US20190040028A1

US20190040028A1 - Arylation of aliphatic amines

Info

Publication number: US20190040028A1
Application number: US16/076,380
Authority: US
Inventors: Frederik Diness; Morten Meldal; Christian Borch Jacobsen
Original assignee: AAA Chemistry Aps
Current assignee: AAA Chemistry Aps
Priority date: 2016-02-08
Filing date: 2017-02-06
Publication date: 2019-02-07
Also published as: BR112017021277A2; US10562872B2; EP3414231A1; EP3414231B1; DK3414216T3; CN108473451B; EP3414216B1; CN108473451A; JP2019506411A; WO2017137048A1; WO2017137047A1; CN109071374A; US20190040027A1; JP6987064B2; ES2819831T3; EP3414216A1

Abstract

The invention relates to a method for arylation of amines, such as aliphatic amines by reaction of aryl-halogens, e.g. chloro- or fluorobenzene derivatives without strongly electron withdrawing substituents in the presence of a strong base.

Description

TECHNICAL FIELD

BACKGROUND OF INVENTION

N-arylations of aliphatic amines are important chemical transformations as the resulting aniline derivatives have found broad applications as pharmaceuticals, materials for organic electronics and dyes for industrial and research applications. Pyrazine and morpholine derivatives are of special interest, as these are found in a range of top selling pharmaceuticals.
A range of transition metal-catalyzed reactions has been developed for the formal halide to nitrogen substitution on aryl halides. Most renowned are the Ullmann and Buchwald-Hartwig couplings employing copper and palladium catalysis respectively. These results notwithstanding, the employment of transition metals as catalysts has several drawbacks in industrial applications, especially due to high costs, oxygen sensitivity, challenging purifications and toxic metal contaminants being present in the final products.
To overcome these shortcomings, catalyst-free S_NAr reactions on highly activated halide-substituted benzene derivatives have been applied. However, the scope of this approach has so far been limited as strongly electron-withdrawing groups, such as nitro or cyano substituents, have been considered essential for reactivity. Thus, leading text books in organic chemistry describes: a) “Without electron-attracting groups present, nucleophilic aromatic substitution occurs only under extreme reaction conditions” F. A. Carey, R. J. Sundberg in Advanced Organic Chemistry: Part A: Structure and Mechanisms; 4th ed. Springer Science and Business Media, New York, 2000. b) “To summarize: Any anion-stabilizing (electron-withdrawing) group ortho or para to a potential leaving group can be used to make nucleophilic aromatic substitution possible.” J. Clayden, N. Greeves, S. Warren, P. Wothers in Organic Chemistry; Oxford University Press, New York, 2001.
WO 2014/191548 discloses a synthetic process for the production of 1-(2-((2,4-dimethyl-phenyl)sulfonyl)phenyl)piperazine by arylation in the presence of Cs₂CO₃. The process however requires incubation at elevated temperature for more than 14 days.

SUMMARY OF INVENTION

The present invention provides catalyst free N-arylation of amines. The methods are very effective, and can typically results in high yields.
Thus, the invention provides methods for preparing an arylated amine, said method comprising the steps of

- a. Providing a nucleophile, wherein said nucleophile comprises an —NH— or an —NH₂group directly linked to only non-aromatic carbon atoms or a salt of said nucleophile;
- b. Providing an electrophile, wherein said electrophile is aryl substituted with at least two substituents, wherein the first substituent is halogen and the second substituent and any further optional substituent(s) are selected from the group consisting of halogen, aryl, substituted aryl, alkenyl, substituted alkenyl, heteroalkenyl, alkyl, substituted alkyl, heteroalkyl, alkoxy, substituted alkoxy, amino, substituted amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl, with the proviso that said aryl is substituted with at the most 4 halogens;
- c. Providing a base, wherein the corresponding acid has a pKa above 32 in DMSO and/or a pKa above 26 in THF;
- d. Providing an organic solvent that only contain protons with a pKa above 32 in DMSO.
- e. Reacting said nucleophile with said electrophile in said organic solvent in the presence of the base, thereby obtaining an arylated amine consisting of said aryl, wherein the first substituent is substituted by said amine;
- f. Optionally purifying the arylated amine.

DESCRIPTION OF DRAWINGS

FIG. 1: Examples of pharmaceuticals containing an N-arylated secondary amine.

FIG. 2 shows the yield of catalyst-free N-arylation of morpholine using various different polyfluorinated benzene derivatives.

FIG. 3 shows the yield of catalyst-free N-arylation of various amines. General reaction conditions used in is: Amine (1.0 eq.), LiHMDS (1.0M in THF, 1.5 eq.) and benzene derivative (1.5 eq.) were mixed and heated.

Compounds

3r, 3s, 3t, 3ad, 3ae, 3af, and 3ag were synthesized by slightly modified procedures.

DETAILED DESCRIPTION OF THE INVENTION

Definitions

The term “alkane” refers to saturated linear or branched carbohydrides of the general formula C_nH_2n+2.
The term “alkenyl” as used herein refers to a substituent derived from an alkene by removal of one —H. An alkene may be any acyclic carbonhydride comprising at least one double bond. Frequently, alkenyl will have the general formula —C_nH_2n−1.
The term “alkyl” refers to a substituent derived from an alkane by removal of one —H.
The term “alkynyl” as used herein refers to a substituent derived from an alkyne by removal of one —H. An alkyne may be any acyclic carbonhydride comprising at least one triple bond. Frequently, alkynyl will have the general formula —C_nH_2n−3.
The term “amino” as used herein refers to a substituent of the general formula
The waved line indicates the point of attachment of the substituent. Amino may thus for example be —NH₂or —NH—.
The term “arene” as used herein refers to aromatic mono- or polycyclic carbonhydrides.
The term “aromatic” refers to a chemical substituent characterised by the following:

- contains a delocalized conjugated π system, most commonly an arrangement of alternating single and double bonds
- has a coplanar structure, with all the contributing atoms in the same plan
- the contributing atoms are arranged in one or more rings
- it contains a number of π delocalized electrons that is even, but not a multiple of 4.

The term “aromatic carbon atom” as used herein refers to a carbon atom, which contributes to an aromatic moiety. Consequently a “non-aromatic carbon atom” is a carbon atom which is not an integral part of an aromatic moiety. Accordingly, a non-aromatic carbon atom may optionally be linked to an aromatic moiety by a covalent bond. By way of examples, all carbon atoms of a phenyl group are considered “aromatic carbon atoms”, however the carbon atoms of an alkyl group covalently linked to phenyl are considered “non-aromatic carbon atoms”.
The term “aryl” as used herein refers to a substituent derived from an arene by removal of one —H from a C in the ring. Examples of useful aryls to be used with the present invention comprise phenyl, napthyl, anthracenyl, phenanthrenyl, and pyrenyl.
The term halogen as used herein refers to a substituent selected from the group consisting of —F, —Cl, —Br and —I.
The term “heteroalkenyl” refers to an alkenyl group, of which one or more carbon has been replaced by a heteroatom selected from S, O and N.
The term “heteroalkyl” refers to a straight- or branched-chain alkyl group, of which one or more carbon has been replaced by a heteroatom selected from S, O and N. Exemplary heteroalkyls include alkyl ethers, secondary and tertiary alkyl amines, and alkyl sulfides.
The term “heteroaryl” as used herein refers to a substituent derived from an heteroarene by removal of one —H from an atom in the ring structure of said heteroarene. Heteroarenes are mono- or polycyclic aromatic compounds comprising one or more heteroatoms in the ring structure. Said heteroatoms are preferably selected from the group consisting of S, N and O. Non limiting examples of useful heteroaryls to be used with the present invention comprise azolyl, pyridinyl, pyrimidinyl, furanyl, and thiophenyl.
The term “non-aromatic heterocycle” refers to a mono- or polycyclic compound, which is not aromatic, and which comprises one or more heteroatom in the ring structure. Said heteroatoms are preferably selected from the group consisting of S, N and O. Examples of non-aromatic heterocycle includes but are not limited to pyrrolidine, piperidine, piperazine, morpholine, and thiomorpholine.
The term “phosphinyl” as used herein refers to a substituent of the general structure
The waved line indicates the point of attachment of the substituent. Thus, phosphinyl may be —PH₃.
The term pKa as used herein refers to the negative logarithmic of the dissociation constant K_afor an acid in a given solvent: pK_a=−Log₁₀K_a.
K_a, also called the acidity constant, is defined as:
$K_{a} = \frac{[A^{-}] [{SH}^{+}]}{[HA] [S]}$
for the reaction:
HA+S
A⁻+SH⁺
wherein S is the solvent and HA is an acid that dissociates into A-, known as the conjugate base of the acid, and a hydrogen ion which combines with a solvent molecule. When the concentration of solvent molecules can be taken to be constant, K_a, is:
$K_{a} = \frac{[A^{-}] [H^{+}]}{[HA]}$
The term “substituted” as used herein in relation to chemical compounds refers to hydrogen group(s) being substituted with another moiety. Thus, “substituted with X” as used herein in relation to chemical compounds refers to hydrogen group(s) being substituted with X. Similarly, “substituted X” refers to X, wherein one hydrogen group has been substituted with another moiety. By way of example “substituted alkyl” refers to alkyl-R, wherein R is any moiety but —H.
The term “substituent” as used herein in relation to chemical compounds refers to an atom or group of atoms substituted in place of a hydrogen atom.
The term “strongly electron withdrawing substituents” as used herein refers to substituents with a Hammet meta substituent constant above 0.5, as described in Hanhsch 1991, and/or substituents having a double bond to oxygen of the linking atom.
The term “thioalkyl” as used herein refers to a substituent of the general formula —S-alkyl.
The term “thioaryl” as used herein refers to a substituent of the general formula —S-aryl.
The term “transition metal catalyst” refers to a compound capable of catalysing a chemical reaction, wherein said compound comprises a transition element or an ion of a transition element. A transition element is an element whose atom has an incomplete d sub-shell, or which can give rise to cations with an incomplete d sub-shell.

Method for Preparing an Arylated Amine

The present invention provides methods for preparing arylated amines. In particular, the methods of the present invention can be performed even in the absence of a transition metal catalyst.
The methods of the invention may comprise the steps of

- a. Providing a nucleophile comprising an —NH— or and —NH₂group, wherein the nucleophile for example may be any of the nucleophiles described herein below in the section “Nucleophile”;
- b. Providing an electrophile comprising an aryl substituted with at least one halogen and optionally further substituents, wherein the electrophile for example may be any of the electrophiles described herein below in the section “Electrophile”,
- c. Providing a base, which for example may be any of the bases described herein below in the section “Base”
- d. Providing an organic solvent, wherein the solvent for example may be the solvent described herein below in the section “Solvent”;
- e. reacting said nucleophile with said electrophile in said organic solvent in the presence of the base, there by obtaining an arylated amine consisting of said aryl, wherein the halogen is substituted by said amine,
- f. Optionally purifying the arylated amine.

The steps a., b., c. and d. may be performed in any suitable order. In one embodiment step e) comprises the sub-steps of

- i) Reacting said nucleophile with said base,
- ii) Reacting the product of sub-step i) with said electrophile,
  wherein sub-steps i) and ii) are performed in the indicated order. This may in particular be the case in embodiments of the invention, where a strong base is used, e.g. a base, wherein the corresponding acid has a pKa above 45, such as above 49.

In case the nucleophile provided in a) comprises more than one —NH— and/or —NH₂group, the amino group mentioned in a) is the amine acting as nucleophile in reaction to obtain the arylated amine.
As mentioned above one advantage of the methods according to the present invention is that the methods can be performed in the absence of a transition metal catalyst. Thus, it is preferred that step e. is performed in the absence of a transition metal catalyst. In some embodiments, it may be preferred that the methods are performed in the absence of any transition metals, and in particular that step e. is performed in the absence of any transition metals. In particular, it may be preferred that the methods are performed in the absence of cupper, palladium and nickel, and in particular that step e. is performed in the absence of any cupper, palladium and nickel. Thus, the reaction, and in particular step e. is preferably performed in the absence of cupper, palladium and nickel in any oxidation state and any form.
Reacting said nucleophile with said electrophile may be done at any useful temperature. Thus, step e. may be performed at any useful temperature. One advantage of the methods of the invention is that the methods generally can be performed at temperatures, which are easy to handle, even in large scare. Thus, reacting said nucleophile with said electrophile may be performed at a temperature of at the most 120° C., such as at the most 110° C. Frequently even lower temperatures can be applied.
Reacting said nucleophile with said electrophile may be done for a time sufficient to allow the reaction. Thus, step e. may be performed for sufficient time to allow the reaction. One advantage of the methods of the invention is that generally a relative short time is required for the reactions. Thus, said nucleophile may typically be allowed to react with said electrophile for at the most one week. Frequently, the reaction may be even faster, thus in some embodiments of the invention, said nucleophile may be allowed to react with said electrophile for at the most 900 min, such as for at the most 720 min, such as for the most 180 min, for example for in the range of 5 to 900 min or in the range of 5 to 720 min.

Nucleophile

The methods of the invention involve reacting a nucleophile and an electrophile. The nucleophile useful with the present invention must comprise an —NH— or and —NH₂group. In general, said nucleophile comprises an —NH— or an —NH₂group directly linked to only non-aromatic carbon atoms.
Thus, in one embodiment the nucleophile contains an —NH— group, which is covalently linked to two non-aromatic carbon atoms. Said non-aromatic carbon atoms may for example be a carbon atom of an alkyl or of an alkyl substituted with one or more substituents. It follows that the nucleophile thus may be a secondary amine.
In another embodiment, said nucleophile comprises an —NH₂group, which is covalently linked to a non-aromatic carbon atom. For example said nucleophile may be alkyl-NH₂or alkyl-NH₂, wherein said alkyl is substituted with one or more substituents. It follows that the nucleophile may be a primary amine.
In one embodiment, the nucleophile may be a compound of the formula I:
wherein
R_aand R_bindividually are selected from the group consisting of —H and alkyl, wherein said alkyl optionally may be substituted with aryl or substituted aryl with the proviso that only one of R_aand R_bmay be —H; or
R_aand R_btogether forms a non-aromatic heterocycle, which optionally may comprise one or more heteroatoms, wherein said heterocycle optionally may be substituted.
Thus, in one embodiment R_amay be selected from the group consisting of —H, C_1-50-alkyl, C_1-10-alkyl-aryl. For example, R_amay be selected from the group consisting of —H, C_1-10-alkyl and C_1-10-alkyl-phenyl. In particular, R_amay be selected from the group consisting of —H, C_1-5-alkyl and —CH₂-phenyl.
In one embodiment R_bmay be selected from the group consisting of C_1-50-alkyl, C_1-10-alkyl-aryl. For example, R_bmay be selected from the group consisting of C_1-10-alkyl and C_1-10-alkyl-phenyl. In particular, R_bmay be selected from the group consisting of C_1-5-alkyl and —CH₂-phenyl.
The nucleophile may also be a compound of formula I, wherein R_aand R_btogether forms a non-aromatic heterocycle, which optionally may comprise one or more heteroatoms, and which may be substituted.
Thus, it is comprised in the invention that the nucleophile may be 4 to 10 membered non-aromatic heterocycle comprising at least one N atom. For example, the nucleophile may be a 4 to 10 membered non-aromatic heterocycle comprising 1 or 2 heteroatoms, wherein at least one is an N atom. Said 4 to 10 membered non-aromatic heterocycle may for example be a monocyclic or a bicyclic non-aromatic heterocycle.
Said 4 to 10 membered non-aromatic heterocycle comprising at least one N atom may optionally be substituted with one or more substituents, e.g. with one or more substituents selected from the group consisting of aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl or substituted alkynyl. For example, said 4 to 10 membered non-aromatic heterocycle may be substituted with one or more substituents selected from the group consisting of C_1-6-alkyl and aryl. For example said 4 to 10 membered non-aromatic heterocycle may be substituted with one substituent selected from the group consisting of phenyl and C_1-3-alkyl, e.g. methyl.
It is also comprised within the invention that the nucleophile may be a 4 to 8 membered non-aromatic heterocycle comprising at least one N atom. Thus, the nucleophile may be a 4 to 8 membered non-aromatic heterocycle comprising only 1 heteroatom, wherein said heteroatom is an N atom. The term “comprising only 1 heteroatom” as used herein refers to that the ring of said heterocycle consists of carbon atoms and said one heteroatom. Said carbon atoms may optionally be substituted. Thus, said 4 to 8 membered non-aromatic heterocycle comprising at least one N atom may optionally be substituted with one or more substituents, e.g. with one or more substituents selected from the group consisting of aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl or substituted alkynyl. For example, said 4 to 8 membered non-aromatic heterocycle may be substituted with one or more substituents selected from the group consisting of C_1-6-alkyl and aryl. For example said 4 to 8 membered non-aromatic heterocycle may be substituted with one substituent selected from the group consisting of phenyl and C_1-3-alkyl, e.g. methyl. Said non-aromatic heterocycle may for example be selected from the group consisting of piperazine, morpholine, tetrahydroisoquinoline, dioxa-azaspiro-decane, piperidine, and thiomorpholine.
In one embodiment of the invention the nucleophile is a compound of the formula II
wherein X is NR_c, NH, O or S.
R_cmay for example be aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, 3 to 8 membered cycloalkyl or 3-8 membered nonaromatic heterocycle. For example, R_cmay be selected from the group consisting of aryl, C_1-10-alkyl, C_2-10-alkenyl, C_2-10-alkynyl and 3-8 membered nonaromatic heterocycle. For example, R_cmay be selected from the group consisting of phenyl, and C_1-10-alkyl.
In one embodiment the nucleophile is selected from the group consisting of: pyrrolidine, N-methylpiperazine, 1-methylpiperazine, 1,4-dioxa-8-azaspiro[4.5]decane, piperidine, piperazine, morpholine, thiomorpholine, 1-phenylpiperazine, N-ethylbutan-1-amine, 1,2,3,4-tetrahydroisoquinoline, dibenzylamine, N-methyl-benzylamine and benzylamine.
In one preferred embodiment the nucleophile is selected from the group consisting of N-methylpiperazine, piperazine, morpholine and 1,2,3,4-tetrahydroisoquinoline. In one preferred embodiment the nucleophile is selected from the group consisting of N-methylpiperazine, piperazine and morpholine.
The nucleophile may also be salts of any of the aforementioned nucleophiles. For example, the nucleophile may be a salt of any of the aforementioned nucleophiles with various inorganic or organic acids. In embodiments of the invention, where the arylated amine is for pharmaceutical use, said salt may be a pharmaceutically acceptable salt.

Electrophile

The methods of the invention involve reacting a nucleophile and an electrophile. The electrophile useful with the present invention comprises or consists of an aryl substituted with at least one halogen and optionally further substituents. Preferably, the electrophile is aryl substituted with at least two substituents, wherein the first substituent is halogen and the second substituent is selected from the group of substituents consisting of halogen, aryl, substituted aryl, alkenyl, substituted alkenyl, heteroalkenyl, alkyl, substituted alkyl, heteroalkyl, alkoxy, substituted alkoxy, amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl, with the proviso that said aryl is substituted with at the most 4 halogens. In addition to said first and second substituents, said aryl may be substituted with one or more additional substituents, which preferably are selected from the same group of substituents as the second substituents.
In one embodiment, the second substituent may also be selected from the group of substituents consisting of halogen, aryl, substituted aryl, alkyl, substituted alkyl, alkoxy, substituted alkoxy, amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl, with the proviso that said aryl is substituted with at the most 4 halogens.
The aryl may be any aryl, for example the aryl may be selected from the group consisting phenyl and naphtalenyl. In preferred embodiments of the invention the aryl is phenyl. Thus, the electrophile may be aryl (e.g. phenyl) substituted with halogen (e.g. —F) and a 2^ndsubstituent. The electrophile may be aryl (e.g. phenyl) substituted with halogen (e.g. —F) and a 2^ndand a 3^rdsubstituent. The electrophile may be aryl (e.g. phenyl) substituted with halogen (e.g. —F) and a 2^nd, a 3^rdand a 4^thsubstituent. The electrophile may be aryl (e.g. phenyl) substituted with halogen (e.g. —F) and a 2^nd, a 3^rd, a 4^thand a 5^thsubstituent. The electrophile may be aryl (e.g. phenyl) substituted with halogen (e.g. —F) and a 2^nd, a 3^rd, a 4^th, a 5^th, and a 6^thsubstituent. Said 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituent may for example be any of the substituents described herein below in this section.
In one embodiment, the electrophile may be a chloro- or fluorobenzene derivative without strongly electron withdrawing substituents.
The electrophile may also be a weakly or non-electron deficient chloro- or fluorobenzene derivative.
The electrophile may also be phenyl substituted with only 2 halogens and optionally a 3^rd, 4^th, 5^thand/or 6^thsubstituent. Thus, in such embodiment the phenyl is covalently linked to exactly two halogens. Said halogen may in particular be —F. In addition, said phenyl may be substituted with a 3^rd, 4^th, 5^thand/or 6^thsubstituent, which is not halogen. The 3^rd, 4^th, 5^thand/or 6^thsubstituent may be any of the substituents described herein below in this section.
The electrophile may also be phenyl substituted with only 1 —F and optionally a 2^nd, 3^rd, 4^th, 5^thand/or 6^thsubstituent. Thus, in such embodiment the phenyl is covalently linked to exactly one —F. In addition, said phenyl may be substituted with a 2^nd, 3^rd, 4^th, 5^thand/or 6^thsubstituent, which is not —F, and preferably not halogen. The 2^nd, 3^rd, 4^th, 5^thand/or 6^thsubstituent may be any of the substituents described herein below in this section.
Said 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituent may be individually selected from the group of consisting of aryl,

R_gO—,

Azolyl- Br—, Cl—, F—, F₃C, R_jS—, and
wherein R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lindividually are selected from the group consisting of —H, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substituted alkynyl. The waved line indicates the point of attachment of the substituent.
Said 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituent may be individually selected from the group consisting of

R_gO—,

Azolyl-, Cl—, F—, and R_jS—,

wherein R_d, R_e, R_f, R_g, R_h, R_iand R_jindividually are selected from the group consisting of —H, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substituted alkynyl. The waved line indicates the point of attachment of the substituent.
Said 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituent may be individually selected from the group consisting of R_gO—,

Cl—, F—, and R_jS—,

wherein R_g, R_h, R_iand R_jindividually are selected from the group consisting of —H, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substituted alkynyl. The waved line indicates the point of attachment of the substituent.
Said 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituent may be individually selected from the group consisting of Cl—, F—, and R_jS—,
wherein R_jis selected from the group consisting of —H, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substituted alkynyl.
In one embodiment electrophile is aryl (e.g. phenyl) substituted with 2 to 4 substituents, wherein all of said substituents are halogen.
The first substituent may be halogen. Preferably, said halogen is selected from the group consisting of —F, —Cl and —Br, more said first substituent is selected from the group consisting of —F and —Cl, for example the first substituent is —F.
In embodiments of the invention, wherein one or more of the 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituents are halogen, then said halogen may be any halogen, preferably said halogen is selected from the group consisting of —F, —Cl and —Br, more preferably said halogen is selected from the group consisting of —F and —Cl.
In one embodiment of the invention the electrophile is aryl (e.g. phenyl) substituted with one or more substituents, where all of said substituents are selected from the group consisting of —F and —Cl.
In embodiments of the invention, wherein one or more of R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lis aryl, said aryl may be selected from the group consisting of phenyl, napthyl, indenyl, and fluorenyl, in particular said aryl may be phenyl.
In embodiments of the invention, wherein one or more of R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lis substituted aryl, said substituted aryl may be selected from the group consisting of phenyl, napthyl, indenyl, and fluorenyl substituted with one or more selected from the group consisting of —OH, aryl, C_1-6-alkyl, C_2-6-alkenyl and C_2-6-alkynyl, in particular said substituted aryl may be phenyl substituted with one or more selected from the group consisting of phenyl, —OH, C_1-6-alkyl, C_2-6-alkenyl and C_2-6-alkynyl.
In embodiments of the invention, wherein one or more of R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lis heteroaryl, said heteroaryl may individually for example be selected from the group consisting of tetrazolyl, imidazolyl, anthracenyl, phenanthrenyl, fluorenyl, pentalenyl, azulenyl, biphenylenyl, furanyl, triazolyl, pyranyl, thiadiazinyl, benzothiophenyl, dihydro-benzo[b]thiophenyl, xanthenyl, isoindanyl, benzhydryl, acridinyl, benzisoxazolyl, quinolinyl, isoquinolinyl, phteridinyl, azepinyl, diazepinyl, imidazolyl, thiazolyl, quinolyl, carbazolyl, pyridinyl, pyridazinyl, imidazolyl, pyrimidinyl, pyrazolyl, triazolyl, pyrazinyl, quinolyl, isoquinolyl, tetrazolyl, furyl, thienyl, isoxazolyl, thiazolyl, oxazolyl, isothiazolyl, pyrrolyl, indolyl, benzimidazolyl, benzofuranyl, cinnolinyl, indazolyl, indolizinyl, phthalazinyl, triazinyl, isoindolyl, purinyl, oxadiazolyl, thiadiazolyl, furazanyl, benzofurazanyl, benzothiophenyl, benzotriazolyl, benzothiazolyl, benzoxazolyl, quinazolinyl, quinoxalinyl, naphthyridinyl, dihydroquinolyl, tetrahydroquinolyl, dihydroisoquinolyl, tetrahydroisoquinolyl, benzofuryl, furopyridinyl, pyrolopyrimidinyl, azaindolyl, imidazolyl, pyrazolyl, pyridyl, pyridazinyl, pyrazinyl, pyrimidinyl, tetrazolyl, pyrazolinyl, and pyrazolidinyl.
In embodiments of the invention, wherein one or more of R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lis substituted heteroaryl, said substituted heteroaryl may individually for example be any of the aforementioned heteroaryl substituted with one or more selected from the group consisting of —OH, aryl, C_1-6-alkyl, C_2-6-alkenyl and C_2-6-alkynyl, in particular substituted with one or more selected from the group consisting of phenyl, —OH, C_1-6-alkyl, C_2-6-alkenyl and C_2-6-alkynyl.
In embodiments of the invention, wherein one or more of R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lis alkyl, said alkyl may individually for example be C_1-10-alkyl, such as C_1-6-alkyl, for example C_1-3-alkyl.
In embodiments of the invention, wherein one or more of R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lis substituted alkyl, said alkyl may individually for example be C_1-10-alkyl, C_1-6-alkyl or C_1-3-alkyl.
In embodiments of the invention, wherein R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand/or R_lis alkyl, said alkyl may for example be C_1-10-alkyl, such as C_1-6-alkyl, for example C_1-3-alkyl, substituted with one or more selected from the group consisting of —OH and aryl, in particular substituted with one or more selected from the group consisting of phenyl and —OH.
In embodiments of the invention, wherein one or more of R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lis substituted alkenyl, said alkenyl may individually for example be C_2-10-alkenyl, C_2-6-alkenyl or C_2-3-alkenyl.
In embodiments of the invention, wherein R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand/or R_lis alkenyl, said alkenyl may for example be C_2-10-alkenyl, such as C_2-6-alkenyl, for example C_2-3-alkenyl, substituted with one or more selected from the group consisting of —OH and aryl, in particular substituted with one or more selected from the group consisting of phenyl and —OH.
In embodiments of the invention, wherein one or more of R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lis substituted alkynyl, said alkynyl may individually for example be C_2-10-alkynyl, C_2-6-alkynyl or C_2-3-alkynyl.
In embodiments of the invention, wherein R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand/or R_lis alkynyl, said alkynyl may for example be C_2-10-alkynyl, such as C_2-6-alkynyl, for example C_2-3-alkynyl, substituted with one or more selected from the group consisting of —OH and aryl, in particular substituted with one or more selected from the group consisting of phenyl and —OH.
In one embodiment, said 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituent may be individually selected from the group of consisting of —NH-alkenyl, —S-alkenyl, —O-alkenyl, —NH—(CH)_n—NH, —O—(CH)_n—NH, —S—(CH)_n—NH, —NH—N—(CH)_n—CH₂, —NH—N═NH, —NH—(CH₂)_n—CH₃, —(CH₂)_n—NH—(CH₂)_m—CH₃, wherein n and m are individually 0 or an integer.
In particular, one substituent may be fused directly with the arene. In other embodiments, the substituent is not fused with the arene.
Two of said 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituents may be fused and thereby forming a ring. Preferably, such fused substituents form a ring selected from the group consisting of pyrrole, furan, thiophene, pyrazole, oxazole, thiazole, imidazole, 1,2,3-triazole, 3,4-dihydro-pyrrole, and 2,3-dihydro-pyrrole rings. In one embodiment, the electrophile is an indole substituted with at least one halogen on the arene. In another embodiment, the electrophile is a benzofuran substituted with at least one halogen on the arene. In yet another embodiment, the electrophile is a benzothiophene substituted with at least one halogen on the arene. In yet another embodiment, the electrophile is an indazole substituted with at least one halogen on the arene. In yet another embodiment, the electrophile is a benzoxazole substituted with at least one halogen on the arene. In yet another embodiment, the electrophile is a benzothiazole substituted with at least one halogen on the arene. In yet another embodiment, the electrophile is a benzimidazole substituted with at least one halogen on the arene. In yet another embodiment, the electrophile is a benzotriazole substituted with at least one halogen on the arene. In yet another embodiment, the electrophile is an isoindoline substituted with at least one halogen on the arene. In yet another embodiment, the electrophile is an indoline substituted with at least one halogen on the arene.
In embodiments of the invention, the electrophile is selected from the group consisting of indole, benzothiophene, benzofuran, benzimidazole, benzoxazole, benzothiazole, indazole, benzotriazole, isoindoline and indoline (shown below), substituted with at least one halogen on the benzene moiety and optionally further substituents. In the cases where a secondary amine is present in the ring fused with the aryl, said secondary amine is preferably first transformed into a tertiary amine, such as being alkylated, alkenylated or arylated.
The electrophile may for example be selected from the group consisting of the following compounds, wherein said compounds are substituted with at least one halogen on the benzene moiety and optionally further substituents:
wherein R_pis selected from the group consisting of hydrogen, alkyl, alkenyl, carbamate, sulfone, benzyl, acetyl, benzoyl, carbobenzyloxy, p-methoxybenzyl carbonyl, tert-butyloxycarbonyl, p-methoxybenzyl, 3,4-dimethoxybenzyl, p-methoxyphenyl, tosyl, and trichloroethyl chloroformate. In some embodiments, R_pis not hydrogen.
In other embodiments, none of the said 2^nd, 3^rd, 4^th, 5^thand 6^thsubstituents are fused with each other.
In one embodiment the electrophile is phenyl substituted with first substituent selected from the group consisting of —F and —Cl, and with a 2^ndsubstituent selected from the group consisting of —F, —Cl, C_1-3-alkoxy, C_1-3-alkyl, thioaryl and phenyl, wherein said thioaryl may be substituted with up to 3 C_1-3-alkyl.
In one embodiment the electrophile is phenyl substituted with first substituent selected from the group consisting of —F, —Cl, C_1-3-alkoxy, C_1-3-alkyl, thioaryl and phenyl, wherein said thioaryl may be substituted with up to 3 C_1-3-alkyl.
In one embodiment the electrophile is selected from the group consisting of tetra-fluorobenzene, trifluorobenzene, difluorobenzene, fluoro-chlorobenzene, dichloro-fluorobenzene, trichlorobenzene, dichlorobenzene, chloro-difluorobenzene, methyl-difluorobenzene, methyl-chloro-fluorobenzene, methoxy-fluorobenzene, di-methyl-thiophenol-fluorobenzene, fluoro-1,1′-biphenyl, N-benzyl-3,5-difluoro-N-methylaniline and bi-phenyl.
In one embodiment the electrophile is selected from 2,3-dichloro-fluorobenzene, 1,2,3-trichlorobenzene, 2-(4,2-di-methyl-thiophenol-yl)-fluorobenzene, and 2-(4,2-di-methyl-thiophenol-yl)-chlorobenzene.
The electrophile may be a product of an organic synthesis and may thus be considered an intermediate. For example, the electrophile may be a product of a cross coupling reaction.

Base

The methods of the present invention involve reacting a nucleophile and an electrophile in the presence of a base. Preferably said base is a base, wherein the corresponding acid has a pKa above 29, such as at least 30 in DMSO. It may also be preferred that said base has a pKa above 25, preferably at least 26 in THF. Thus, it is generally preferred that the base is not a weak base, for example the base is preferably not Cs₂CO₃.
In some embodiments of the invention the base may be a base, wherein the corresponding acid has a pKa above 32 in DMSO. In some embodiments the base may be a base, wherein the corresponding acid has a pKa above 26 in THF.
In some embodiments of the invention it may be preferred that the base is not too strong. Thus, in some embodiments it is preferred that the base is a base, wherein the corresponding acid has a pKa in the range of 29 to 49, such as in the range of 29 to 45. In other embodiments the base is a base, wherein the corresponding acid has a pKa in the range of 32 to 49, such as in the range of 32 to 45. Aforementioned pKa is preferably determined in DMSO.
pKa may be determined by any conventional method. pKa values in DMSO is preferably measured up to the value of 35, and values above 35 may be extrapolated as described in Bordwell, Acc. Chem. Res. 1988, 21, 456-463.
The corresponding acid to butyllithium (BuLi) has a pKa 50, and may thus in some embodiments be less preferable. Thus, in some embodiments the base is a base, wherein the corresponding acid has a pKa above 29, for example above 32, with the proviso that the base is not BuLi.
In some embodiments, the base is a metal hydride, such as an alkali metal hydride. In some embodiments, the base is selected from the group consisting of lithium hydride, sodium hydride, potassium hydride, cesium hydride, magnesium hydride, calcium hydride, lithium aluminium hydride, sodium aluminium hydride, potassium aluminium hydride, lithium borohydride, sodium borohydride and potassium borohydride.
In one embodiment the base is selected from the group consisting of lithium bis(trimethylsilyl)amide (LiHMDS), sodium bis(trimethylsilyl)amide (NaHMDS), potassium bis(trimethylsilyl)amide (KHMDS), lithium 2,2,6,6,-tertmethylpiperidide (LiTMP), and BuLi.
In some embodiments, the base is a non-nucleophilic base, i.e. a base only acting as a nucleophile in the removal of protons. Typical non-nucleophilic bases are sterically hindered and bulky, preventing them from attacking as nucleophiles. Hence, protons can attach to the basic center of the base but alkylation and complexation is inhibited. Examples of non-nucleophilic bases are lithium diisopropylamide (LDA), LiTMP and silicon-based amides such as LiHMDS, NaHMDS and KHMDS. Generally, non-nucleophilic bases are sterically hindered and bulky, and thus the base may be a base having a M_wof at least 120 g/mol, preferably of at least 130 g/mol, such as of at least 140 g/mol. More preferably the base has aforementioned Mw and aforementioned pKa. Thus, it may be preferred that the base has:

- a pKa above 29 in DMSO and/or a pKa in THF above 25; and
- a Mw of at least 120 g/mol or a M_wof at least 140 g/mol.

In other embodiments the base is selected from the group consisting of LiHMDS, NaHMDS, KHMDS and LiTMP.

Solvent

The methods of the present invention involve reacting a nucleophile and an electrophile in a solvent and in the presence of a base. The solvent may be any organic solvent.
In one embodiment the solvent may be chosen according to the base used in the particular reaction. Thus, the solvent may be an organic solvent, which is stable in the presence the base employed under the reaction conditions employed.
In addition, it is preferred that the solvent is a liquid at the reaction temperature.
It is preferred that the solvent is a solvent that only contain protons with a pKa above 35.1 in DMSO. In one embodiment the solvent is a solvent that only contains protons with a pKa above 32 in DMSO. In one embodiment the solvent is not DMSO. Thus, the solvent may be a solvent that only contains protons with a pKa above 32 in DMSO, with the proviso that the solvent is not DMSO.
In one embodiment the solvent is a solvent that does not contain any carbonyl groups. In one embodiment the solvent is a solvent that does not contain any sulfoxide groups.
The solvent may for example be selected from the group consisting of ethers, alkanes, benzene and substituted benzene.
Ethers useful as solvent include any ether. In particular, the ether may be an ether, which only contain protons with a pKa above 32, for example above 35.1 in DMSO. It may further be preferred that the ether is a liquid at the reaction temperature. It may further be preferred that the ether does not contain any carbonyl groups. The ether may for example be selected from the group consisting of tetrahydrofuran (THF), dioxane, dimethoxyethane (DME), 2-methyl-tetrahydrofuran (2-Me-THF), and diethoxyethane.
Alkanes useful as solvent include any alkane. In particular, the alkane may be an alkane, which only contain protons with a pKa above 32, for example above 35.1 in DMSO. It may further be preferred that the alkane is a liquid at the reaction temperature. It may further be preferred that the alkane does not contain any carbonyl groups. The alkane may be a linear, branched or cyclic alkane, e.g. a C_4-20linear, branched or cyclic alkane. For example, the alkane may be methylcyclohexane.
Substituted benzenes useful as solvent include any substituted benzene. In particular, the substituted benzene may be a substituted benzene, which only contain protons with a pKa above 32, for example above 35.1 in DMSO. It may further be preferred that the substituted benzene is a liquid at the reaction temperature. It may further be preferred that the substituted benzene does not contain any carbonyl group. The substituted benzene is in general different from the electrophile used in the reaction. However in some embodiments, the electrophile may also be used as solvent. For example the substituted benzene may be substituted with one or more substituents selected from the group consisting of C_1-3-alkyl. In addition or alternatively, the benzene may be substituted with up to 1 —Cl. The substituted benzene may for example be selected from the group consisting of toluene, xylene and chlorobenzene.

Arylated Amine

The arylated amine to be prepared by the methods according to the invention may be any of the electrophiles described herein above, wherein in place of the first substituent, the aryl of the electrophile is covalently N-linked to one of the nucleophiles described herein above.
In one embodiment of the invention the arylated amine is selected from the group of compounds shown in FIG. 2 as compounds 3c, 3d, 3e, 3f, 3g, 3h, 3i, 3j, 3l and 3m.
In one embodiment of the invention the arylated amine is selected from the group of compounds shown in FIG. 3 as compounds 3n, 3o, 3p, 3q, 3r, 3s, 3t, 3u, 3v, 3w, 3x, 3y, 3z, 3aa, 3ab, 3ac, 3ad, 3ae, 3af and 3ag.
In one embodiment the arylated amine is selected from the group of compounds shown in FIG. 1.
The arylated amine may be used in further organic synthesis, and thus in some embodiments the arylated amine may be an intermediate. Thus, the arylated amine may be a substrate for further functionalization e.g. through cross coupling reactions. In other embodiments the arylated amine may be a final product. The arylated amine may be purified by any conventional method including for example extraction, precipitation, crystallisation, distillation and/or chromatography.

EXAMPLES

The invention is further illustrated by the following examples, which however should not be construed as being limiting for the invention.

Example 1

In the following examples, N-arylation of amines was performed as follows unless otherwise specified:
To a vial was added amine nucleophile (1.0 mmol) and base. If nothing else is specified the base employed was LiHMDS (1.0 M in THF, 1.5 mL). The vial was sealed and stirred at the designated temperature for 10 minutes. To this mixture was then added fluoro electrophile (1.5 mmol) at room temperature. The reaction was stirred at the designated temperature until judged complete by HPLC. The reaction was then quenched by addition of solid NaHCO₃and loaded directly onto a silica gel column. The product was purified by flash chromatography on silica gel using a suitable mixture of ethyl acetate and heptane as eluent.

Example 2

N-arylation of compound 1a (N-methylpiperazine) with compound 2 (1,3,5-trifluorobenzene) was performed using the following general reaction conditions: 1a (0.2 mmol) and the base (0.5 mmol) was mixed in solvent (0.5 mL) at room temperature. Different solvents, bases and temperatures were tested.
After 10 minutes 2 (0.6 mmol) was added and reaction heated to temperature and stirred for 12 h. Yields assessed by HPLC. The results are shown in table 1 below.

TABLE 1

		M_w	pK_a	pK_a			Yield 3a
Entry	Base	(g/mol)	DMSO	THF	Solvent	Temperature	(%)^a

A	None	—	—	—	THF	50° C.	0
B	Cs₂CO₃	325.82	**	**	THF	50° C.	0
C	LiO^tBu	80.05	29		THF	50° C.	<5**
D	LiHMDS	167.33	30***	26	THF	50° C.	>95
E*	LiTMP	147.19	37		THF	90° C.	42 (3b)
F	LiHMDS	167.33	30***	26	DME	50° C.	73
G	LiHMDS	167.33	30***	26	2-Me-THF	50° C.	51

^aEvaluated by HPLC.
*1-fluoro-3-methoxybenzene used instead of 1,3,5-trifluorobenzene.
**pKa of Cs₂CO₃is expected to be lower than 29 in DMSO and 25 in THF.
***pKa of LiHMDS has been reported to be 30 in DMSO (http://www.d-bernier.fr/pKa.php)

The reaction was successfully performed using LiOtBu as base, but it was significantly less efficient than using some of the other bases.

Example 3

The scope of arylation reactions with respect to the fluorobenzenes in reaction with morpholine 1 b was investigated, and the results are provided in FIG. 2. Polyfluorinated benzene derivates perform well in these reactions as seen from the formation of products 3c-3m, which was isolated in yields up to 93%. Important notions about these reactions are the ability to achieve mono-substitution in the presence of additional fluorine atoms as well as the high degree of regioselectivity. For example, product 3c is formed as a single regioisomer even though the starting 1,2,3,5-tetrafluorobenzene contains no less than three distinct fluorine atoms. Difluorinated benzenes can also be employed as electrophiles in the reactions as illustrated by the formation of 3f and 3g isolated in 81% and 86% yield, respectively.
The general reaction conditions used in this example: Morpholine 1 b (1.0 mmol), LiHMDS (1.0M in THF, 1.5 mL) and fluorobenzene derivative (1.5 mmol) was mixed and heated. Details regarding the individual reactions are given below.
The structure of the compounds is provided in FIG. 2.

Compound 3c, 4-(2,3,5-trifluorophenyl)morpholine

Synthesized from 1,2,3,5-tetrafluorobenzene according to the general procedure.
After 3 hours at room temperature the compound 3c was isolated in 70% yield as an off-white solid. ¹H NMR (CDCl₃) δ ppm 6.58-6.48 (m, 1H), 6.41 (ddt, J=11.2, 5.6, 2.6 Hz, 1H), 3.90-3.81 (m, 4H), 3.12-3.07 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 157.9 (ddd, J=243.5, 13.4, 3.3 Hz), 151.3 (ddd, J=247.4, 15.3, 13.5 Hz), 142.1 (ddd, J=10.5, 6.8, 3.5 Hz), 140.5 (ddd, J=242.9, 14.1, 4.6 Hz), 100.7 (dt, J=26.1, 2.4 Hz), 97.7 (dd, J=27.7, 21.9 Hz), 66.7, 50.5 (d, J=3.8 Hz).

Compound 3d, 4-(2,5-difluorophenyl)morpholine

Synthesized from 1,2,4-trifluorobenzene according to the general procedure.
After 14 hours at 50° C. the compound 3d was isolated in 73% yield as a yellowish solid. ¹H NMR (CDCl₃) δ ppm 6.96 (ddd, J=12.1, 8.7, 5.2 Hz, 1H), 6.73-6.44 (m, 2H), 3.95-3.73 (m, 4H), 3.16-2.89 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 159.1 (dd, J=241.9, 2.2 Hz), 151.6 (dd, J=241.2, 2.9 Hz), 141.0 (dd, J=10.5, 8.8 Hz), 116.5 (dd, J=23.6, 10.0 Hz), 107.9 (dd, J=23.9, 8.3 Hz), 105.8 (dd, J=26.3, 3.5 Hz), 66.8, 50.5 (d, J=3.8 Hz).

Compound 3e, 4-(3,5-difluorophenyl)morpholine

Synthesized from 1,3,5-trifluorobenzene according to the general procedure.
After 14 hours at 50° C. the compound 3e was isolated in 76% yield as a yellowish solid. ¹H NMR (CDCl₃) δ ppm 6.39-6.32 (m, 2H), 6.28 (tt, J=8.8, 2.2 Hz, 1H), 3.86-3.79 (m, 4H), 3.16-3.11 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 164.0 (dd, J=244.4, 15.8 Hz), 153.3 (t, J=12.2 Hz), 98.3-97.0 (m), 94.5 (t, J=26.1 Hz), 66.5, 48.3.

Compound 3f, 4-(2-fluorophenyl)morpholine

Synthesized from 1,2-difluorobenzene according to the general procedure.
After 2.5 hours at 100° C. the compound 3f was isolated in 81% yield as a dark yellow oil. ¹H NMR (CDCl₃) δ ppm 7.10-7.00 (m, 2H), 6.98-6.91 (m, 2H), 3.89-3.83 (m, 4H), 3.10-3.06 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 155.7 (d, J=246.1 Hz), 139.9 (d, J=8.4 Hz), 124.4 (d, J=3.6 Hz), 122.6 (d, J=8.1 Hz), 118.6 (d, J=2.9 Hz), 116.1 (d, J=20.6 Hz), 67.0, 50.9 (d, J=3.4 Hz).

Compound 3g, 4-(3-fluorophenyl)morpholine

Synthesized from 1,3-difluorobenzene according to the general procedure.
After 2.5 hours at 100° C. the compound 3g was isolated in 86% yield as a dark yellow oil. ¹H NMR (CDCl₃) δ ppm 7.21 (td, J=8.2, 6.9 Hz, 1H), 6.67 (dd, J=8.3, 2.2 Hz, 1H), 6.61-6.53 (m, 2H), 3.88-3.81 (m, 4H), 3.19-3.12 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 163.8 (d, J=243.4 Hz), 152.9 (d, J=9.8 Hz), 130.1 (d, J=10.0 Hz), 110.7 (d, J=2.5 Hz), 106.2 (d, J=21.4 Hz), 102.4 (d, J=25.1 Hz), 66.7, 48.8.

Compound 3h, 4-(2-chlorophenyl)morpholine

Synthesized from 1-chloro-2-fluorobenzene according to the general procedure.
After 1.5 hours at 100° C. the compound 3h was isolated in 72% yield as a yellow oil. ¹H NMR (CDCl₃) δ ppm 7.37 (dd, J=7.9, 1.5 Hz, 1H), 7.24 (td, J=7.7, 1.6 Hz, 1H), 7.04 (dd, J=8.1, 1.5 Hz, 1H), 6.99 (td, J=7.7, 1.6 Hz, 1H), 3.88 (t, J=4.6 Hz, 4H), 3.06 (t, J=4.6 Hz, 4H). ¹³C NMR (CDCl₃) δ ppm 149.0, 130.7, 128.8, 127.6, 123.9, 120.2, 67.1, 51.6.

Compound 3i, 4-(4-chlorophenyl)morpholine

Synthesized from 1-chloro-4-fluorobenzene according to the general procedure.
After 14 hours at 80° C. the compound 3i was isolated in 53% yield as a white solid. ¹H NMR (CDCl₃) δ ppm 7.25-7.15 (m, 2H), 6.86-6.80 (m, 2H), 3.87-3.82 (m, 4H), 3.14-3.07 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 149.9, 129.0, 124.9, 116.9, 66.8, 49.3.

Compound 3j, 4-(2-chloro-5-methylphenyl)morpholine

Synthesized from 1-chloro-2-fluoro-4-methylbenzene according to the general procedure.
After 14 hours at 90° C. the compound 3j was isolated in 77% yield as a clear oil. ¹H NMR (CDCl₃) δ ppm 7.23 (d, J=8.0 Hz, 1H), 6.84 (d, J=2.0 Hz, 1H), 6.82-6.77 (m, 1H), 3.97-3.72 (m, 4H), 3.13-2.93 (m, 4H), 2.32 (s, 3H). ¹³C NMR (CDCl₃) δ ppm 148.6, 137.5, 130.3, 125.5, 124.5, 120.9, 67.1, 51.6, 21.1.

Compound 3l, 4-(3-methoxyphenyl)morpholine

Synthesized from 1-fluoro-3-methoxybenzene according to the general procedure.
After 14 hours at 90° C. the compound 3l was isolated in 93% yield as a bright yellow oil. ¹H NMR (CDCl₃) δ ppm 7.24-7.16 (m, 1H), 6.54 (ddd, J=8.3, 2.3, 0.9 Hz, 1H), 6.48-6.42 (m, 2H), 3.88-3.82 (m, 4H), 3.80 (s, 3H), 3.19-3.11 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 160.6, 152.6, 129.8, 108.4, 104.6, 102.1, 66.8, 55.1, 49.2.

Compound 3m, 4-([1,1′-biphenyl]-4-yl)morpholine

Synthesized from 4-fluoro-1,1′-biphenyl according to the general procedure.
After 14 hours at 100° C. the compound 3m was isolated in 65% yield as a yellowish solid. ¹H NMR (CDCl₃) δ ppm 7.62-7.51 (m, 4H), 7.45-7.39 (m, 2H), 7.33-7.28 (m, 1H), 7.02-6.97 (m, 2H), 3.93-3.85 (m, 4H), 3.26-3.18 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 150.5, 140.8, 132.6, 128.7, 127.8, 126.5, 126.5, 115.7, 66.9, 49.2.
The reactions proved to be selective to fluorine substitution over chlorine-substitution in derivatives containing both, leading to e.g. 3h-3j. Such structural motifs are in themselves important for the pharmaceutical industry (see examples of pharmaceutically important compounds in FIG. 1), while the chlorine substituent may also provide a site for further functionalization e.g. through cross coupling reactions. It should be stressed that the benzyne mechanism is ruled out for the here presented reactions as no or negligible regioisomers are observed in NMR spectra of the crude reaction mixtures.
Of special interests were the findings that no additional halogen substituents were required and that even electron-rich fluorobenzene derivatives are feasible reaction partners. Simply adding LiHMDS in THF and fluorobenzene to a vial containing morpholine 1 b provides product 3k in 82% yield. Employing 3-fluoroanisole under similar conditions forms the product 3l, which can be isolated in 93% yield. Formation of product 3l from morpholine have previously (Desmartes 2002, Katoka 2002, Maes 2004, Urgaonkar 2004, Lerma 2005, Shen 2008, Otsuka 2010, Guo 2010, Lu 2011, Jacobsen 2016) been accomplished by employing, nickel, copper, palladium or ruthenium catalysis utilizing 3-halogen-substituted anisole derivatives. Product 3m further illustrates the complementary properties of these reactions to cross coupling reactions. This product may be synthesized by a cross coupling reaction of 4-chloro-fluorobenzene and phenyl boronic acid followed by the here presented catalyst-free reaction with morpholine, or in the vice versa reaction order through initial generation of 3i followed by a cross coupling reaction.

Example 4

The methods are useful for arylation of a range of secondary amines as seen in FIG. 3. Both cyclic and acyclic secondary amines can be functionalized as illustrated by formation of products 3n-3ag in high yields. Thus, most of these compounds were obtained with a 75-80% yield. Moreover, pyrazine and 1-methylpyrazine can be employed as nucleophiles and the resultant products 3q and 3r isolated in 62 and 72% yield, respectively. As seen in FIG. 1 both mono- and diarylated pyrazines are common substructures in pharmaceutical substances. Interestingly, by simply increasing the amount of base and electrophile, the reaction switched from mono- to bis-substitution on pyrazine to afford 3r or 3s respectively.
General reaction conditions used in this example: Amine (1.0 mmol), LiHMDS (1.0M in THF, 1.5 mmol) and benzene derivative (1.5 mmol) was mixed and heated.
The structure or the compounds is provided in FIG. 3.

Compound 3n, 1-(3-fluorophenyl)pyrrolidine

Synthesized from pyrrolidine and 1,3-difluorobenzene according to the general procedure.
After 3 hours at 80° C. the compound 3n was isolated in 80% yield yellow oil. ¹H NMR (CDCl₃) δ ppm 7.14 (td, J=8.2, 6.9 Hz, 1H), 6.39-6.28 (m, 2H), 6.24 (dt, J=12.4, 2.4 Hz, 1H), 3.30-3.21 (m, 4H), 2.08-1.97 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 164.1 (d, J=241.6 Hz), 149.5 (d, J=11.0 Hz), 130.0 (d, J=10.5 Hz), 107.3 (d, J=2.1 Hz), 101.7 (d, J=21.7 Hz), 98.4 (d, J=25.4 Hz), 47.7, 25.4.

Compound 3o, N-benzyl-3,5-difluoro-N-methylaniline

Synthesized from N-methyl-benzylamine and 1,3,5-trifluorobenzene according to the general procedure. After 14 hours at 50° C. the compound 3o was isolated in 79% yield as a dark yellow oil. ¹H NMR (CDCl₃) δ ppm 7.36-7.32 (m, 2H), 7.30-7.23 (m, 1H), 7.22-7.14 (m, 2H), 6.28-6.17 (m, 2H), 6.14 (tt, J=9.1, 2.2 Hz, 1H), 4.52 (s, 2H), 3.03 (s, 3H). ¹³C NMR (CDCl₃) δ ppm 164.2 (dd, J=242.9, 16.3 Hz), 151.6 (t, J=13.2 Hz), 137.7, 128.7, 127.2, 126.4, 95.2-94.6 (m), 91.4 (t, J=26.3 Hz), 56.2, 38.7.

Compound 3p, N-benzyl-3-methoxy-N-methylaniline

Synthesized from N-methyl-benzylamine and 1-fluoro-3-methoxybenzene according to the general procedure. After 14 hours at 90° C. the compound 3p was isolated in 75% yield as a clear oil. ¹H NMR (CDCl₃) δ ppm 7.38-7.31 (m, 2H), 7.31-7.22 (m, 3H), 7.16 (td, J=8.1, 2.0 Hz, 1H), 6.46-6.38 (m, 1H), 6.37-6.31 (m, 2H), 4.56 (s, 2H), 3.80 (s, 3H), 3.04 (s, 3H). ¹³C NMR (CDCl₃) δ ppm 160.7, 151.1, 138.9, 129.8, 128.5, 126.8, 126.7, 105.5, 101.3, 98.9, 56.5, 55.0, 38.5.

Compound 3q, 1-(2-fluorophenyl)-4-methylpiperazine

Synthesized from N-methyl-piperazine and 1,2-difluorobenzene according to the general procedure. After 3 hours at 80° C. the reaction was quenched by the addition of HCl (0.01M in H₂O), the solvent evaporated and the compound redissolved in CH₃CN:H₂O (1:1). The compound 3q was isolated as the HCl salt by VLC on C18 gel (0 to 50% CH₃CN in 0.01M HCl) in 62% yield as light brown solid. ¹H NMR (DMSO-d₆) δ ppm 11.37 (s, 1H), 7.24-6.95 (m, 4H), 3.51-3.40 (m, 4H), 3.25-3.12 (m, 4H), 2.78 (d, J=4.8 Hz, 3H). ¹³C NMR (DMSO-d₆) δ ppm 154.84 (d, J=244.3 Hz), 138.29 (d, J=8.6 Hz), 124.97 (d, J=3.4 Hz), 123.40 (d, J=7.9 Hz), 119.63 (d, J=2.6 Hz), 116.14 (d, J=20.3 Hz), 52.27, 47.00 (d, J=3.4 Hz), 41.98.

Compound 3r, 1-(3-methoxyphenyl)piperazine

Synthesized according to a modified procedure. Piperazine (3.0 mmol), LiHMDS (1.0M in THF, 1.5 mmol) and 1-fluoro-3-methoxybenzene (1.0 mmol) was mixed and heated. After 3 hours at 80° C. the reaction was quenched by the addition of HCl (0.01M in H₂O), the solvent evaporated and the compound redissolved in CH₃CN:H₂O (1:1). The compound 3r was isolated as the HCl salt by VLC on C18 gel (0 to 50% CH₃CN in 0.01M HCl) in 72% yield as light brown solid. ¹H NMR (DMSO-d₆) δ ppm 9.19 (s, 2H), 7.15 (t, J=8.2 Hz, 1H), 6.56 (dd, J=8.2, 2.3 Hz, 1H), 6.51 (t, J=2.4 Hz, 1H), 6.45 (dd, J=8.1, 2.3 Hz, 1H), 3.72 (s, 3H), 3.43-3.25 (m, 4H), 3.27-3.07 (m, 4H). ¹³C NMR (DMSO-d₆) δ ppm 160.23, 150.94, 129.91, 108.65, 105.77, 102.45, 55.01, 45.60, 42.29.

Compound 3s, 1,4-bis(3-fluorophenyl)piperazine

Synthesized according to a modified procedure. Piperazine (1.0 mmol), LiHMDS (1.0M in THF, 3.0 mmol) and 1,3-difluorobenzene (3.0 mmol) was mixed and heated.
After 3 hours at 80° C. the compound 3s was isolated in 72% yield as a bright yellow solid. ¹H NMR (CDCl₃) δ ppm 7.23 (td, J=8.2, 6.9 Hz, 2H), 6.73 (ddd, J=8.4, 2.4, 0.8 Hz, 2H), 6.64 (dt, J=12.2, 2.4 Hz, 2H), 6.57 (tdd, J=8.2, 2.4, 0.8 Hz, 2H), 3.34 (s, 8H). ¹³C NMR (CDCl₃) δ ppm 163.8 (d, J=243.6 Hz), 152.7 (d, J=9.8 Hz), 130.2 (d, J=9.9 Hz), 111.4 (d, J=2.6 Hz), 106.3 (d, J=21.4 Hz), 103.0 (d, J=25.0 Hz), 48.7.

Compound 3t, 1-(2,3-dichlorophenyl)piperazine

Synthesized according to a modified procedure. Piperazine (3.0 mmol), LiHMDS (1.0M in THF, 3.0 mmol) and 2,3-dichlorofluorobenzene (1.0 mmol) was mixed and heated.
After 12 hours at 50° C. the reaction was quenched by the addition of HCl (0.01M in H₂O), the solvent evaporated and the compound redissolved in CH₃CN:H₂O (1:1). The compound 3t was isolated as the HCl salt by VLC on C18 gel (0 to 50% CH3CN in 0.01M HCl) in 66% yield as white solid.
Employing 1,2,3-trichlorobenzene as electrophile instead of 2,3-dichlorofluorobenzene the same product was obtained in 51% yield after 22 hours at 65° C. ¹H NMR (DMSO-d₆) δ ppm 9.50 (s, 2H), 7.42-7.30 (m, 2H), 7.20 (dd, J=7.2, 2.3 Hz, 1H), 3.22 (s, 8H). ¹³C NMR (DMSO-d₆) δ ppm 150.00, 132.69, 128.62, 126.15, 125.20, 119.82, 47.78, 42.98.

Compound 3u, 8-(3-methoxyphenyl)-1,4-dioxa-8-azaspiro[4.5]decane

Synthesized from 1,4-dioxa-8-azaspiro[4.5]decane and 1-fluoro-3-methoxybenzene according to the general procedure. After 14 hours at 90° C. the compound 3u was isolated in 90% yield as a yellow oil. ¹H NMR (CDCl₃) δ ppm 7.16 (t, J=8.2 Hz, 1H), 6.56 (ddd, J=8.2, 2.4, 0.8 Hz, 1H), 6.49 (t, J=2.4 Hz, 1H), 6.40 (ddd, J=8.1, 2.4, 0.8 Hz, 1H), 3.98 (s, 4H), 3.79 (s, 3H), 3.39-3.27 (m, 4H), 1.88-1.77 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 160.50, 152.19, 129.66, 109.24, 107.11, 104.04, 102.81, 64.23, 55.05, 47.51, 34.40.

Compound 3v, 1-(3,5-difluorophenyl)piperidine

Synthesized from piperidine and 1,3,5-trifluorobenzene according to the general procedure. After 14 hours at 50° C. the compound 3v was isolated in 61% yield as a clear oil. ¹H NMR (CDCl₃) δ ppm 6.46-6.27 (m, 2H), 6.19 (tt, J=8.9, 2.2 Hz, 1H), 3.23-3.04 (m, 4H), 1.72-1.47 (m, 6H). ¹³C NMR (CDCl₃) δ ppm 164.03 (dd, J=243.2, 16.1 Hz), 153.65 (t, J=12.4 Hz), 98.96-96.87 (m), 93.12 (t, J=26.2 Hz), 49.40, 25.32, 24.18.

Compound 3w, 1-(3-methoxyphenyl)-4-phenylpiperazine

Synthesized from 1-phenylpiperazine and 1-fluoro-3-methoxybenzene according to the general procedure. After 14 hours at 90° C. the compound 3w was isolated in 73% yield as an off-white solid. ¹H NMR (CDCl₃) δ ppm 7.34-7.27 (m, 2H), 7.22 (t, J=8.2 Hz, 1H), 7.02-6.97 (m, 2H), 6.91 (tt, J=7.3, 1.1 Hz, 1H), 6.62 (ddd, J=8.3, 2.4, 0.8 Hz, 1H), 6.54 (t, J=2.4 Hz, 1H), 6.47 (ddd, J=8.2, 2.4, 0.8 Hz, 1H), 3.82 (s, 3H), 3.35 (s, 8H). ¹³C NMR (CDCl₃) δ ppm 160.60, 152.60, 151.19, 129.83, 129.15, 120.03, 116.30, 109.04, 104.72, 102.74, 55.19, 49.34.

Compound 3x, 1-(2-chlorophenyl)-4-phenylpiperazine

Synthesized from 1-phenylpiperazine and 1-chloro-2-fluorobenzene according to the general procedure. After 2.5 hours at 100° C. the compound 3x was isolated in 50% yield as a white solid. ¹H NMR (CDCl₃) δ ppm 7.41 (dd, J=8.0, 1.5 Hz, 1H), 7.35-7.29 (m, 2H), 7.29-7.22 (m, 1H), 7.11 (dd, J=8.0, 1.6 Hz, 1H), 7.05-6.98 (m, 3H), 6.91 (ddt, J=8.4, 7.3, 1.1 Hz, 1H), 3.41-3.36 (m, 4H), 3.26-3.21 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 151.35, 149.12, 130.68, 129.12, 128.84, 127.60, 123.84, 120.35, 119.85, 116.21, 51.30, 49.49.

Compound 3y, N-butyl-N-ethyl-3-methoxyaniline

Synthesized from N-ethylbutan-1-amine and 1-fluoro-3-methoxybenzene according to the general procedure. After 14 hours at 90° C. the compound 3y was isolated in 82% yield as a clear oil. ¹H NMR (CDCl₃) δ ppm 7.17 (td, J=8.5, 1.0 Hz, 1H), 6.40-6.31 (m, 1H), 6.33-6.19 (m, 2H), 3.40 (q, J=7.1 Hz, 2H), 3.34-3.24 (m, 2H), 1.69-1.57 (m, 2H), 1.45-1.36 (m, 2H), 1.20 (t, J=6.9 Hz, 3H), 1.02 (t, J=7.4 Hz, 3H). ¹³C NMR (CDCl₃) δ ppm 160.86, 149.36, 129.80, 105.01, 99.78, 98.32, 55.02, 50.20, 44.96, 29.71, 20.35, 13.99, 12.32.

Compound 3z, 8-(3,5-difluorophenyl)-1,4-dioxa-8-azaspiro[4.5]decane

Synthesized from 1,4-dioxa-8-azaspiro[4.5]decane and 1,3,5-trifluorobenzene according to the general procedure. After 14 hours at 50° C. the compound 3z was isolated in 76% yield as an yellow oil. ¹H NMR (CDCl₃) δ ppm 6.43-6.30 (m, 2H), 6.25-6.12 (m, 1H), 3.98 (s, 4H), 3.41-3.25 (m, 4H), 1.84-1.69 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 164.02 (dd, J=243.7, 16.1 Hz), 152.48 (t, J=12.4 Hz), 106.89, 99.15-97.06 (m), 93.50 (t, J=26.2 Hz), 64.36, 46.59, 34.08.

Compound 3aa, 2-(2-chlorophenyl)-1,2,3,4-tetrahydroisoquinoline

Synthesized from 1,2,3,4-tetrahydroisoquinoline and 1-chloro-2-fluorobenzene according to the general procedure. After 2.5 hours at 100° C. the compound 3aa was isolated in 74% yield as an yellow oil. ¹H NMR (CDCl₃) δ ppm 7.59-7.38 (m, 1H), 7.38-7.14 (m, 6H), 7.12-6.87 (m, 1H), 4.34 (s, 2H), 3.47 (t, J=5.8 Hz, 2H), 3.10 (t, J=5.9 Hz, 2H). ¹³C NMR (CDCl₃) δ ppm 149.17, 134.75, 134.57, 130.76, 129.04, 128.88, 127.56, 126.43, 126.36, 125.84, 123.64, 120.69, 53.32, 49.99, 29.16.

Compound 3ab, N-butyl-N-ethyl-3,5-difluoroaniline

Synthesized from N-ethylbutan-1-amine and 1,3,5-trifluorobenzene according to the general procedure. After 14 hours at 50° C. the compound 3ab was isolated in 41% yield as a clear oil. ¹H NMR (CDCl₃) δ ppm 6.19-5.98 (m, 3H), 3.32 (q, J=7.1 Hz, 2H), 3.25-3.14 (m, 2H), 1.63-1.49 (m, 2H), 1.42-1.31 (m, 2H), 1.15 (t, J=7.1 Hz, 3H), 0.97 (t, J=7.3 Hz, 3H). ¹³C NMR (CDCl₃) δ ppm 164.41 (dd, J=241.7, 16.7 Hz), 149.98 (t, J=13.3 Hz), 94.43-93.37 (m), 90.09 (t, J=26.5 Hz), 50.28, 45.12, 29.46, 20.26, 13.92, 12.08.

Compound 3ac, N,N-dibenzyl-3-methoxyaniline

Synthesized from dibenzylamine and 1-fluoro-3-methoxybenzene according to the general procedure. After 14 hours at 90° C. the compound 3ac was isolated in 89% yield as a clear oil. ¹H NMR (CDCl₃) δ ppm 7.40-7.32 (m, 4H), 7.32-7.20 (m, 6H), 7.11 (td, J=8.2, 1.4 Hz, 1H), 6.41 (ddd, J=8.4, 2.3, 1.2 Hz, 1H), 6.36-6.28 (m, 2H), 4.67 (s, 4H), 3.76-3.68 (m, 3H). ¹³C NMR (CDCl₃) δ ppm 160.73, 150.59, 138.50, 129.86, 128.60, 126.85, 126.61, 105.61, 101.49, 99.07, 54.99, 54.20.

Compound 3ad, N-benzyl-2-chloroaniline

Synthesized by a modified procedure. Benzyl amine (2.5 mmol), LiHMDS (1.0M in THF, 2.5 mmol) and 2-chlorofluorobenzene (0.5 mmol) were mixed and heated. After 3 hours at 100° C. the compound 3ad was isolated in 42% yield as a clear oil. ¹H NMR (CDCl₃) δ ppm 7.26-7.21 (m, 4H), 7.20-7.15 (m, 2H), 6.98 (td, J=7.8, 1.5 Hz, 1H), 6.56-6.49 (m, 2H), 4.64 (d, J=5.7 Hz, 1H), 4.29 (d, J=5.7 Hz, 2H). ¹³C NMR (CDCl₃) δ ppm 143.82, 138.71, 129.07, 128.68, 127.76, 127.31, 127.23, 119.07, 117.38, 111.47, 47.81.

Compound 3ae, N-benzyl-3,5-difluoroaniline

Synthesized by a modified procedure. Benzyl amine (2.5 mmol), LiHMDS (1.0M in THF, 2.5 mmol) and 1,3,5-trifluorobenzene (0.5 mmol) were mixed and heated. After 14 hours at 50° C. the compound 3ae was isolated in 41% yield as an yellow oil. ¹H NMR (CDCl₃) δ ppm 7.42-7.27 (m, 5H), 6.21-6.08 (m, 3H), 4.30 (s, 2H), 4.28 (s, 1H). ¹³C NMR (CDCl₃) δ 164.16 (dd, J=244.2, 16.0 Hz), 150.28 (t, J=13.3 Hz), 138.23, 128.82, 127.61, 127.42, 96.68-94.46 (m), 92.60 (t, J=26.1 Hz), 48.08.

Compound 3af, 4-(4-methylpiperazin-1-yl)benzothiophene-2-carboxylic acid

Synthesized by a modified procedure. N-methyl-piperazine (0.2 mmol), 4-fluoro-1-benzothiophene-2-carboxylic acid (0.1 mmol) and LiHMDS (1.0 M in THF, 0.25 mmol) were mixed and heated. After 14 hours at 65° C. the reaction was quenched by the addition of HCl (1.0 M in H₂O), the solvent evaporated and the compound redissolved in CH₃CN:H₂O (1:1). The compound 3af was isolated as the HCl salt by chromatography on C18 gel (0 to 50% CH₃CN in 0.01M HCl) in 31% yield as white solid.
¹H NMR (500 MHz, DMSO-d6) δ 13.53 (s, 1H), 10.74 (s, 1H), 8.04 (s, 1H), 7.73 (d, J=8.2 Hz, 1H), 7.46 (t, J=7.9 Hz, 1H), 7.05 (d, J=7.6 Hz, 1H), 3.60-3.48 (m, 4H), 3.42-3.31 (m, 2H), 3.24-3.12 (m, 2H), 2.86 (d, J=4.7 Hz, 3H). ¹³C NMR (126 MHz, DMSO) δ 163.4, 148.1, 142.9, 133.7, 132.9, 128.0, 127.5, 118.0, 113.6, 52.7, 48.9, 42.1.

Compound 3ag, 1-methyl-6-(4-phenylpiperazin-1-yl)-indole

Synthesized by a modified procedure. 1-Phenylpiperazine (0.2 mmol), 6-fluoro-1-methyl-indole (0.1 mmol) and LiHMDS (1.0 M in THF, 0.2 mmol) were mixed and heated. After 14 hours at 90° C. in a sealed tube the reaction was quenched by the addition of HCl (1.0 M in H₂O), the solvent evaporated and the compound redissolved in CH₃CN:H₂O (1:1). The compound 3ag was isolated as the HCl salt by chromatography on C18 gel (0 to 50% CH₃CN in 0.01 M HCl) in 53% yield as white solid.
¹H NMR (500 MHz, DMSO-d6) δ 8.07 (s, 1H), 7.70 (d, J=8.5 Hz, 1H), 7.65-7.54 (m, 1H), 7.51 (d, J=3.1 Hz, 1H), 7.40-7.24 (m, 3H), 7.18-7.07 (m, 2H), 6.98-6.90 (m, 1H), 6.52 (d, J=3.2 Hz, 1H), 3.91-3.67 (m, 11H). ¹³C NMR (126 MHz, DMSO) δ 149.3, 135.8, 132.0, 129.2, 129.1, 121.3, 120.2, 116.3, 116.1, 112.2, 103.0, 100.7, 54.5, 46.5, 32.7.

Example 5

Compound 4, N-benzyl-3-fluoro-N-methyl-5-morpholinoaniline

N-benzyl-3,5-difluoro-N-methylaniline (3o) (0.5 mmol), morpholine (1.0 mmol) and LiHMDS (1.0M in THF, 1.0 mmol) were mixed and heated. After 24 hours at 100° C. the compound 4 was isolated in 62% yield as a bright yellow oil. ¹H NMR (CDCl₃) δ ppm 7.37-7.29 (m, 2H), 7.29-7.19 (m, 3H), 6.06-5.97 (m, 3H), 4.52 (s, 2H), 3.85-3.78 (m, 4H), 3.13-3.07 (m, 4H), 3.02 (s, 3H). ¹³C NMR (CDCl₃) δ ppm 164.9 (d, J=238.5 Hz), 153.4 (d, J=12.5 Hz), 151.6 (d, J=13.2 Hz), 138.5, 128.6, 127.0, 126.6, 95.0 (d, J=1.7 Hz), 91.8 (d, J=18.1 Hz), 91.6 (d, J=17.3 Hz), 66.8, 56.5, 49.2, 38.7.
A two steps reaction applying first a weaker nucleophile followed by an amine nucleophile also proved viable (scheme 2). Applying imidazole as the weak azole nucleophile followed by addition of morpholine provided derivative 7, which is a substructure in metabotropic glutamate 5 receptor antagonists with nanomolar activity. Thiophenol also proved highly applicable in this approach, illustrated by the synthesis of recently marketed pharmaceutical antidepressant Vortioxetine 9 from 1,2-difluorobenzene. This should be compared to the present industrial production process, which utilizes two subsequent cross-coupling reactions on 2-bromo-iodobenzene.

Compound 6, 1-(3,5-difluorophenyl)-1H-imidazole

To a vial was added imidazole (1.0 mmol), 1,3,5-trifluorobenzene (2.0 mmol), Cs₂CO₃(3.0 mmol) and dimethylacetamide (2.0 mL). The vial was sealed and stirred at 120° C. for 12 hours. The reaction was quenched with water and brine and then extracted into Et₂O. After evaporation, the product 6 was purified by chromatography on silica gel (EtOAC), and isolated in 75% yield as a white solid. ¹H NMR (CDCl₃) δ ppm 7.90 (t, J=1.1 Hz, 1H), 7.27 (t, J=1.4 Hz, 1H), 7.23 (t, J=1.2 Hz, 1H), 7.01-6.93 (m, 2H), 6.83 (tt, J=8.7, 2.3 Hz, 1H). ¹³C NMR (CDCl₃) δ ppm 163.6 (dd, J=250.7, 14.1 Hz), 139.2 (t, J=12.2 Hz), 135.3, 130.99, 117.8, 105.5-104.1 (m), 102.9 (t, J=25.3 Hz).

Compound 7, 4-(3-fluoro-5-(1H-imidazol-1-yl)phenyl)morpholine

Morpholine (0.5 mmol), 1-(3,5-difluorophenyl)-1H-imidazole (6) (0.6 mmol) and LiHMDS (1.0M in THF, 1.2 mmol) were mixed and heated. After 2 hours at 80° C. the compound 7 was isolated by flash chromatography (5% EtOH in EtOAc) in 71% yield as a yellowish solid. ¹H NMR (CDCl₃) δ ppm 7.82 (t, J=1.2 Hz, 1H), 7.23 (t, J=1.4 Hz, 1H), 7.18 (d, J=1.2 Hz, 1H), 6.63 (d, J=2.2 Hz, 1H), 6.60-6.51 (m, 2H), 3.91-3.81 (m, 4H), 3.26-3.15 (m, 4H). ¹³C NMR (CDCl₃) δ ppm 164.2 (d, J=245.0 Hz), 153.5 (d, J=11.4 Hz), 139.2 (d, J=13.0 Hz), 135.6, 130.5, 118.3, 103.7 (d, J=2.5 Hz), 100.8 (d, J=25.4 Hz), 99.9 (d, J=25.6 Hz), 66.5, 48.3.

Compound 8, 2-(2,4-di-methyl-thiophenol-yl)-fluorobenzene

To a vial was added 2,4-dimethylthiophenol (1.0 mmol), 1,2-difluorobenzene (2.0 mmol), Cs₂CO₃(2.5 mmol) and dimethylacetamide (2.0 mL). The vial was sealed and stirred at 140° C. for 4 hours. The reaction was quenched with water and brine and then extracted into Et₂O. After evaporation, the product 8 was purified by VLC on silica gel, and isolated in 87% yield as a clear oil. ¹H NMR (CDCl₃) δ ppm 7.28 (d, J=7.8 Hz, 1H), 7.19-7.09 (m, 2H), 7.09-7.03 (m, 1H), 7.02-6.95 (m, 2H), 6.87 (td, J=7.7, 1.7 Hz, 1H), 2.37 (s, 3H), 2.34 (s, 3H). ¹³C NMR (CDCl₃) δ ppm 160.0 (d, J=245.2 Hz), 141.0, 138.9, 134.4, 131.7, 130.2 (d, J=1.9 Hz), 127.7, 127.6, 127.5 (d, J=7.5 Hz), 124.6 (d, J=3.5 Hz), 124.4, 115.5 (d, J=21.8 Hz), 21.1, 20.5.

Compound 9, 1-[2-(2,4-Dimethyl-phenylsulfanyl)-phenyl]piperazine

Piperazine (1.25 mmol), 2-(2,4-di-methyl-thiophenol-yl)-fluorobenzene (8) (0.25 mmol) and LiHMDS (1.0 M in THF, 1.0 mmol) were mixed and heated in a sealed vial. After 2 hours at 80° C. the reaction was quenched by the addition of HCl (0.01M in H₂O), the solvent evaporated and the compound redissolved in CH₃CN:H₂O (1:1). The compound 9 was isolated as the HCl salt by VLC on C18 gel (0 to 50% CH₃CN in 0.01M HCl) in 53% yield as white solid. ¹H NMR (DMSO-d₆) δ ppm 9.41 (s, 2H), 7.33 (d, J=7.8 Hz, 1H), 7.24 (d, J=1.9 Hz, 1H), 7.16-7.07 (m, 3H), 6.96 (ddd, J=7.9, 5.9, 2.7 Hz, 1H), 6.44-6.39 (m, 1H), 3.21 (s, 8H), 2.32 (s, 3H), 2.24 (s, 3H). ¹³C NMR (DMSO-d₆) δ 147.8, 141.6, 139.3, 135.7, 133.3, 131.7, 128.1, 126.8, 126.0, 125.8, 125.1, 120.2, 48.1, 43.3, 20.7, 20.1.
The invention provides a novel method for the amination of unactivated fluorobenzene derivatives. A key factor for reactivity is the applied base's ability to sufficiently deprotonate the amine nucleophile under the applied reaction conditions without simultaneously degrading the fluorobenzene electrophile. For secondary aliphatic amines the reactions proceed readily by addition of a simple base such as LiHMDS, and thus circumvent the need for transition metals. The reactions proceed with great regio- and chemoselectivity and are compatible with a broad range of additional substituents including alkyl, aryl, alkoxy, amine, azolyl, thioethers, fluorine and chlorine. The versatility of these new reactions was illustrated by the synthesis of a variety of anilines including the antidepressant Vortioxetine.

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Claims

1. A method for preparing an arylated amine, said method comprising the steps of

a. Providing a nucleophile, wherein said nucleophile comprises an —NH— or an —NH₂group directly linked to only non-aromatic carbon atoms or a salt of said nucleophile;

b. Providing an electrophile, wherein said electrophile is aryl substituted with at least two substituents, wherein the first substituent is halogen and the second substituent and any further optional substituent(s) are selected from the group consisting of halogen, aryl, substituted aryl, alkenyl, substituted alkenyl, heteroalkenyl, alkyl, substituted alkyl, heteroalkyl, alkoxy, substituted alkoxy, amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl, with the proviso that said aryl is substituted with at the most 4 halogens;

c. Providing a base, wherein the corresponding acid has a pKa above 29 in DMSO and/or a pKa above 25 in THF;

d. Providing an organic solvent that only contain protons with a pKa above 32 in DMSO.

e. Reacting said nucleophile with said electrophile in said organic solvent in the presence of the base, thereby obtaining an arylated amine consisting of said aryl, wherein the first substituent is substituted by said amine;

f. Optionally purifying the arylated amine,

wherein steps a., b., c. and d. may be performed in any order.

2. The method according to claim 1, wherein step e. is performed in the absence of a transition metal catalyst.

3. The method according to claim 1, wherein step b. consists of providing an electrophile, wherein said electrophile is aryl substituted with at least two substituents, wherein the first substituent is halogen and the second substituent and any further optional substituent(s) are selected from the group consisting of halogen, aryl, substituted aryl, alkyl, substituted alkyl, alkoxy, substituted alkoxy, amino, substituted amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl, with the proviso that said aryl is substituted with at the most 4 halogens.

4. The method according to any one of the preceding claims, wherein step e. comprises the sub-steps of i) reacting said nucleophile with said base and ii) reacting the product of step i) with said electrophile, and wherein sub-steps i) and ii) are performed in the indicated order.

5. The method according to claim 4, wherein the base used is a strong base, such as a base wherein the corresponding acid has a pKa above 45, such as above 49.

6. The method according to any one of the preceding claims, wherein the nucleophile is an alkyl amine or a salt thereof.

7. The method according to any one of the preceding claims, wherein the nucleophile is a secondary amine or a salt thereof.

8. The method according to any one of the preceding claims, wherein the nucleophile is a compound of the formula I:

wherein

R_aand R_bindividually are selected from the group consisting of —H and alkyl, wherein said alkyl optionally may be substituted with aryl or substituted aryl with the proviso that only one of R_aand R_bmay be —H; or

R_aand R_btogether forms a non-aromatic heterocycle, which comprises one or more heteroatoms,

or a salt thereof.

9. The method according to claim 8, wherein R_aand R_bindividually are selected from the group consisting of alkyl, wherein said alkyl optionally may be substituted with aryl; or

R_aand R_btogether forms a non-aromatic heterocycle, which optionally may comprise one or more heteroatoms

or a salt thereof.

10. The method according to any one of claims 8 to 9, wherein R_ais selected from the group consisting of —H, C_1-10-alkyl, C_1-10-alkyl-aryl, for example, wherein R_ais selected from the group consisting of —H, C_1-5-alkyl and alkyl-phenyl, such as —CH₂-phenyl.

11. The method according to any one of claims 8 to 10, wherein R_bis selected from the group consisting of C_1-10-alkyl, C_1-10-alkyl-aryl, for example wherein R_bis selected from the group consisting of C_1-5-alkyl and alkyl-phenyl, such as —CH₂— phenyl.

12. The method according any one of the preceding claims, wherein the nucleophile is 4 to 10 membered non-aromatic heterocycle comprising at least one N atom or a salt thereof.

13. The method according any one of the preceding claims, wherein the nucleophile is 4 to 10 membered non-aromatic heterocycle comprising 1 or 2 heteroatoms, wherein at least one is an N atom.

14. The method according any one of the preceding claims, wherein the nucleophile is 4 to 8 membered non-aromatic heterocycle comprising exactly 2 heteroatoms, wherein at least one is an N atom.

15. The method according to any one of the preceding claims, wherein the nucleophile is a compound of the formula II

wherein X is NR_c, NH, O or S.

16. The method according to claim 15, wherein R_cis aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl, substituted alkynyl, 3 to 8 membered cycloalkyl or 3-8 membered nonaromatic heterocycle.

17. The method according to any one of the preceding claims, wherein the nucleophile is selected from the group consisting of piperazine, morpholine and salts hereof.

18. The method according to any one of the preceding claims, wherein the nucleophile is selected from the group consisting of N-methylpiperazine, morpholine, pyrrolidine, N-methyl-benzylamine, piperazine, 1,4-dioxa-8-azaspiro[4.5]decane, piperidine, 1-phenylpiperazine, N-ethylbutan-1-amine, 1,4-dioxa-8-azaspiro[4.5]decane, 1,2,3,4-tetrahydroisoquinoline, dibenzylamine, benzyl amine and imidazole.

19. The method according to any one of the preceding claims, wherein said second substituent is a substituent selected from the group of consisting of aryl,

R_gO—,

Azolyl- Br—, Cl—, F—, F₃C, R_jS—, and

wherein R_d, R_e, R_f, R_g, R_h, R_i, R_j, R_kand R_lindividually are selected from the group consisting of —H, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substituted alkynyl.

20. The method according to any one of the preceding claims, wherein said second substituent is a substituent selected from the group consisting of

R_gO—,

Azolyl-, Cl—, F—, and R_jS—,

wherein R_d, R_e, R_f, R_g, R_h, R_iand R_jindividually are selected from the group consisting of —H, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substituted alkynyl.

21. The method according to any one of the preceding claims, wherein said second substituent is a substituent selected from the group consisting of R_gO—,

Cl—, F—, and R_jS—,

wherein R_g, R_h, R_iand R_jindividually are selected from the group consisting of —H, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substituted alkynyl.

22. The method according to any one of the preceding claims, wherein said second substituent is a substituent selected from the group consisting of Cl—, F—, and R_jS—,

wherein R_jis selected from the group consisting of —H, aryl, substituted aryl, heteroaryl, substituted heteroaryl, alkyl, substituted alkyl, alkenyl, substituted alkenyl, alkynyl and substituted alkynyl.

23. The method according to any one of the preceding claims, wherein the electrophile is aryl substituted with 2 to 6 substituents, wherein the first substituent is halogen and the 2^nd, 3^rd, 4^th, 5^thand/or 6th substituent individually are selected from the group consisting of halogen, aryl, substituted aryl, alkenyl, substituted alkenyl, heteroalkenyl, alkyl, substituted alkyl, heteroalkyl, alkoxy, substituted alkoxy, amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl,

24. The method according to any one of the preceding claims, wherein the electrophile is arene substituted with 2 to 4 substituents, wherein the first substituent is halogen and the 2^nd, 3^rdand 4^thsubstituent individually are selected from the group consisting of halogen, aryl, substituted aryl, alkenyl, substituted alkenyl, heteroalkenyl, alkyl, substituted alkyl, heteroalkyl, alkoxy, substituted alkoxy, amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl.

25. The method according to any one of the preceding claims, wherein the electrophile is benzene substituted with 2 halogens and optionally a 3^rd, 4^th, 5^thand/or 6^thsubstituent, wherein said 3^rd, 4^th, 5^thand/or 6^thsubstituent individually are selected from the group consisting of halogen, aryl, substituted aryl, alkenyl, substituted alkenyl, heteroalkenyl, alkyl, substituted alkyl, heteroalkyl, alkoxy, substituted alkoxy, amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl.

26. The method according to any one of the preceding claims, wherein the electrophile is benzene substituted with 1 —F, a 2^ndsubstitutent and optionally a 3^rd, 4^th, 5^thand/or 6^thsubstituent, wherein said 2^nd, 3^rd, 4^th, 5^thand/or 6^thsubstituent individually are selected from the group consisting of —Cl, aryl, substituted aryl, alkenyl, substituted alkenyl, heteroalkenyl, alkyl, substituted alkyl, heteroalkyl, alkoxy, substituted alkoxy, amino, thioalkyl, substituted thioalkyl, thioaryl, substituted thioaryl, heteroaryl, and phosphinyl.

27. The method according to any one of claims 23 to 26, wherein the 2^nd, 3^rd, 4^th, 5^thand/or 6th substituent individually are selected from the group consisting of substituents defined in any one of claims 19 to 22.

28. The method according to any one of the preceding claims, wherein the electrophile is aryl substituted with 2 to 4 substituents, wherein all of said substituents are halogen.

29. The method according to any one of the preceding claims, wherein two of said substituents are fused to form a ring.

30. The method according to any one of the preceding claims, wherein said arene of the electrophile is benzene.

31. The method according to any one of the preceding claims, wherein halogen is selected from the group consisting of —F, —Cl and —Br.

32. The method according to any one of the preceding claims, wherein said first substituent is selected from the group consisting of —F and —Cl.

33. The method according to any one of the preceding claims, wherein said first substituent and any additional substituents are selected from the group consisting of —F and —Cl.

34. The method according to any one of the preceding claims, wherein said electrophile is selected from 2,3-dichloro-fluorobenzene, 1,2,3-trichlorobenzene, 2-(2,4-di-methyl-thiophenol-yl)-fluorobenzene, and 2-(2,4-di-methyl-thiophenol-yl)-chlorobenzene.

35. The method according to any one of the preceding claims, wherein the electrophile is selected from the group consisting of 1,3,5-trifluorobenzene, 1,2,3,5-tetrafluorobenzene, 1,2,4-trifluorobenzene, 1,2-difluorobenzene, 1,3-difluorobenzene, 1-chloro-2-fluorobenzene, 1-chloro-4-fluorobenzene, 1-chloro-2-fluoro-4-methylbenzene, 1-fluoro-3-methoxybenzene, 4-fluoro-1,1′-biphenyl, 2,3-dichlorofluorobenzene, 2-chlorofluorobenzene, 4-fluoro-1-benzothiophene-2-carboxylic acid, 6-fluoro-1-methyl-indole, N-benzyl-3,5-difluoro-N-methylaniline, and 1-(3,5-difluorophenyl)-1H-imidazole.

36. The method according to any one of the preceding claims, wherein alkyl is C_1-10-alkyl, preferably C_1-6-alkyl.

37. The method according to any one of the preceding claims, wherein alkenyl is C_2-10-alkenyl, preferably C_2-6-alkenyl.

38. The method according to any one of the preceding claims, wherein alkynyl is C_2-10-alkynyl, preferably C_2-6-alkynyl.

39. The method according any one of the preceding claims, wherein aryl is phenyl.

40. The method according to any one of the preceding claims, wherein said substituents are selected from the group consisting of —NH-alkenyl, —S-alkenyl, —O-alkenyl, —NH—(CH)n-NH, —O—(CH)n-NH, —S—(CH)n-NH, —NH—N—(CH)n-CH2, —NH—N═NH, —NH—(CH2)n-CH3, —(CH2)n-NH—(CH2)m-CH3, wherein n and m are individually 0 or an integer.

41. The method according to any one of the preceding claims, wherein said electrophile is selected from the group consisting of indole, benzothiophene, benzofuran, benzimidazole, benzoxazole, benzothiazole, indazole, benzotriazole, isoindoline and indoline (shown below), substituted with at least one halogen on the benzene moiety and optionally further substituents.

42. The method according to any one of the preceding claims, wherein the solvent is a solvent that only contains protons with a pKa above 35.1 in DMSO.

43. The method according to any one of the preceding claims, wherein the solvent contains no carbonyl groups.

44. The method according to any one of the preceding claims, wherein the solvent contains no sulfoxide groups.

45. The method according to any one of the preceding claims, wherein the solvent is selected from the group consisting of ethers, alkanes, benzene and substituted benzene.

46. The method according to claim 45, wherein the ether is selected from the group consisting of tetrahydrofuran (THF), dioxane, dimethoxyethane (DME), and 2-methyl-tetrahydrofuran (2-Me-THF).

47. The method according to claim 45, wherein the alkane is an alkane, which is a liquid at the reaction temperature.

48. The method according to any one of claims 45 and 47, wherein the alkane is methylcyclohexane.

49. The method according to claim 45, wherein the substituted benzene is benzene substituted with one or more substituents selected from the group consisting of C_1-3-alkyl and —Cl, wherein said benzene is substituted with at the most 1 —Cl.

50. The method according to any one of claims 45 and 49, wherein the substituted benzene is selected from the group consisting of xylene, toluene and chlorobenzene.

51. The method according to any one of the preceding claims, wherein the base is a base wherein the corresponding acid has a pKa of less than 45 in THF.

52. The method according to any one of the preceding claims, wherein the base has a molecular weight (M_w) of at least 120 g/mol, such as at least 130 g/mol, such as at least 140 g/mol.

53. The method according to any one of the preceding claims, wherein the base has a pKa higher than 29 in DMSO and/or a pKa higher than 25 in THF, and a M_wof at least 120 g/mol, such as at least 140 g/mol.

54. The method according to any one of the preceding claims, wherein the base is selected from the group consisting of LiHMDS, NaHMDS, KHMDS, LiTMP, and BuLi.

55. The method according to any one of the preceding claims, wherein the base is selected from the group consisting of LiHMDS, NaHMDS, KHMDS and LiTMP.

56. The method according to any one of the preceding claims, wherein the reaction in step e. is performed at a temperature of at the most 120° C., such as at the most 110° C.

57. The method according to any one of the preceding claims, wherein the reaction of step e. takes places for at the most one week.

58. The method according to any one of the preceding claims, wherein the reaction of step e. takes places for in the range of 5 to 900 min, such as 5 to 720 min.

59. The method according to any one of the preceding claims, wherein said arylated amine is obtained as a salt thereof.