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GB2283971A - Preparation of 2-alkoxycycloalkanone - Google Patents

Preparation of 2-alkoxycycloalkanone Download PDF

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Publication number
GB2283971A
GB2283971A GB9423015A GB9423015A GB2283971A GB 2283971 A GB2283971 A GB 2283971A GB 9423015 A GB9423015 A GB 9423015A GB 9423015 A GB9423015 A GB 9423015A GB 2283971 A GB2283971 A GB 2283971A
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GB
United Kingdom
Prior art keywords
enantiomer
process according
oxidation
alkoxycycloalkanone
oxidising agent
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Granted
Application number
GB9423015A
Other versions
GB2283971B (en
GB9423015D0 (en
Inventor
Raymond Mccague
David Chaplin
Robin Bannister
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Chirotech Technology Ltd
Original Assignee
Chiroscience Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Chiroscience Ltd filed Critical Chiroscience Ltd
Publication of GB9423015D0 publication Critical patent/GB9423015D0/en
Publication of GB2283971A publication Critical patent/GB2283971A/en
Application granted granted Critical
Publication of GB2283971B publication Critical patent/GB2283971B/en
Anticipated expiration legal-status Critical
Expired - Fee Related legal-status Critical Current

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    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C49/00Ketones; Ketenes; Dimeric ketenes; Ketonic chelates
    • C07C49/385Saturated compounds containing a keto group being part of a ring
    • C07C49/517Saturated compounds containing a keto group being part of a ring containing ether groups, groups, groups, or groups
    • CCHEMISTRY; METALLURGY
    • C07ORGANIC CHEMISTRY
    • C07CACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C45/00Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
    • C07C45/27Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation
    • C07C45/30Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by oxidation with halogen containing compounds, e.g. hypohalogenation

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  • Chemical & Material Sciences (AREA)
  • Organic Chemistry (AREA)
  • Organic Low-Molecular-Weight Compounds And Preparation Thereof (AREA)
  • Low-Molecular Organic Synthesis Reactions Using Catalysts (AREA)

Abstract

A process for preparing an enantiomer of a 2-alkoxycycloalkanone comprises contacting a corresponding 2-alkoxycyclohexanol enantiomer with an oxidising agent, under conditions promoting the oxidation, wherein the oxidising agent is a hypohalite or a source thereof.

Description

OXIDATION PROCESS 2-Alkoxycycloalkanones in single-enantiomer form are important as pharmaceutical intermediates. For instance, EP-A-0416952 and EP-A-0416953 disclose that (S)-2-methoxycyclohexanone is a precursor of tricyclic B-lactam antibiotics.
Czech Patent Publication No. 265359/1990 discloses that the singleenantiomer 2-alkoxycycloalkanones can be obtained by oxidation of the hydroxyl group in the corresponding 2-alkoxycycloalkanols that are prepared, in turn, by a technique such as resolution of the racemate, e.g. by biocatalysis of an ester.
However, difficulty exists in the finding of an oxidation procedure that is scaleable and does not promote racemisation of the configurationally-labile product. For instance, the reported oxidation procedure of 2-alkoxycyclohexanols to the ketones using zinc chromite catalyst at over 3000C would certainly promote racemisation and, additionally, use of basic reaction conditions would result in racemised ketone product. Chromic acid is effective at the oxidation without promoting racemisation but the stoichiometric use of chromium is unacceptable on environmental grounds and similar difficulties emerge with other metal-based oxidation procedures.
According to the present invention, it has been found that using hypohalorite as oxidant gives a surprisingly high yielding oxidation, with minimal racemisation, in a conversion as represented in Scheme 1. The procedure is scaleable and economic.
In Scheme 1, n indicates that the ring is of 5-8 C atoms, Rl is C,10 alkyl and R2 represents H or optional substituent(s) in the ring which do not directly affect the oxidation reaction. A particularly valuable case is where R2 is a substituent vicinal to the hydroxyl function, prepared for example by opening of the 2,3-epoxy-1 -alkoxycycloalkanone with an alkyl (R2) nucleophile. Configuration at the hydroxyl group could be cis or trans to the adjacent alkoxy substituent, depending on the mode of preparation; for instance, if prepared by reaction of a cycloalkane epoxide with an alcohol (R'OH), the hydroxyl group would be trans to the alkoxy.The configuration at the alkoxy function could be as indicated in Scheme 1 or, equally, as the opposite enanriomer The reaction is preferably conducted using simply an oxidising mixture of a hypohalite, e.g. hypochlorite, or a source thereof which generates the hypohalite in situ. For example, the oxidising agent may be an aqueous solution of sodium hypochlorite or, for example, calcium hypochlorite, an organic solvent, and an acid.
The hypochlorite source may be bleaching powder. The acid is any that can provide a pH < 2; examples are sulphuric acid, hydrochloric acid, phosphoric acid and potassium hydrogen sulphate. Preferred solvents possess a ketone function, such as acetone, methyl ethyl ketone or methyl isobutyl ketone.
The following Example illustrates the invention.
ExamDle A solution of lS,S]-2-methoxycyclohexanol (194 g, 1.5 mol) in acetone (1164 ml) was added to a stirred mixture of orthophosphoric acid (85%; 291 g, 2.45 mol) in water (11 64 ml). With the mixture maintained at less than 250C and pH < 1.7, sodium hypochlorite solution (8% min. available chlorine, 1261 ml) was added over 1-2 h. The mixture was then stirred for a further 0.5 h and excess oxidant destroyed by the addition of sodium metabisulphite until the mixture no longer darkened start-iodide paper. A further amount of sodium metabisulphite was added (5 g) and the product extracted with methyl tert-butyl ether (4 x 450 ml).The combined extracts were washed with 30% sodium chloride solution (660 ml), dried over magnesium sulphate and concentrated under vacuum to give the product (as 180 ml being a 90% solution of product).
The following Table shows the results from a series of experiments, using a variety of related reaction conditions.
TABLE SHOWING RESULTS FROM MCH EXPERIMENTATION
No Oxidant Solvent* Acid Complete? EE+ 2 equiv 1 5% NaOCl MEK H2SO4 100% 97 1 equiv 2 " xI n N HOAc 0% NA 3 " " " " KHSO4 0% NA 0.4 equiv 4 " " NONE " " 0% NA 5 * n MEK KHSO4 95% 96% 4 equiv 6 " " " " NaHSO4 75% NA 7 " " MEK KHSO4 50% NA 2,2 equiv 8 " " DCM " " 50% NA 9 " " Heptane H2SO4 10% NA 1 equiv 10 " " NONE " " 40% NA 11 " " MEK H2SO4 98% 97% 12 " " MIBK " " 97% 91% 13 " " MEK " " 100% 97% 14 " " Acetone " " 100% 97% 15 8% NaOCl " " " " 97% 93% 16 " " " " H3PO4 100% 97% 17 " " " " HCl 100% 97% 18 " " " " H3PO4 100% 97% 19 " " " " HCl 95% 96% 20 Ca(OCl)2 " " H3PO4 82% NA * MEK = methyl ethyl ketone (2-butanone) DCM = dichloromethane MIBK = methyl isobutyl ketone + Enantiomeric excess of recovered ketone product Scheme 1

Claims (6)

  1. CLAIMS 1. A process for preparing an enantiomer of a 2-alkoxycycloalkanone by contacting a corresponding 2-alkoxycyclohexanol enantiomer with an oxidising agent, under conditions promoting the oxidation, wherein the oxidising agent is a hypohalite or a source thereof.
  2. 2. A process according to claim 1, which is conducted in the presence of an acid, providing acidity at least equivalent to 2.2 eq. KHSO4.
  3. 3. A process according to claim 2, which is conducted in the presence of a solvent.
  4. 4. A process according to claim 3, wherein the solvent is a ketone.
  5. 5. A process according to any preceding claim, wherein the product is an enantiomer of 2-methoxycyclohexanone.
  6. 6. A process according to any preceding claim, wherein the oxidising agent is a hypochlorite.
GB9423015A 1993-11-16 1994-11-15 Oxidation process Expired - Fee Related GB2283971B (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB939323632A GB9323632D0 (en) 1993-11-16 1993-11-16 Oxidation process

Publications (3)

Publication Number Publication Date
GB9423015D0 GB9423015D0 (en) 1995-01-04
GB2283971A true GB2283971A (en) 1995-05-24
GB2283971B GB2283971B (en) 1997-11-26

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GB939323632A Pending GB9323632D0 (en) 1993-11-16 1993-11-16 Oxidation process
GB9423015A Expired - Fee Related GB2283971B (en) 1993-11-16 1994-11-15 Oxidation process

Family Applications Before (1)

Application Number Title Priority Date Filing Date
GB939323632A Pending GB9323632D0 (en) 1993-11-16 1993-11-16 Oxidation process

Country Status (1)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998000382A1 (en) * 1996-07-02 1998-01-08 Toray Industries, Inc. Processes for the preparation of optically active ketones

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4005932A1 (en) * 1990-02-25 1991-08-29 Bayer Ag Cycloalkanone(s) prepn., useful as plant protectant intermediates

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE4005932A1 (en) * 1990-02-25 1991-08-29 Bayer Ag Cycloalkanone(s) prepn., useful as plant protectant intermediates

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1998000382A1 (en) * 1996-07-02 1998-01-08 Toray Industries, Inc. Processes for the preparation of optically active ketones

Also Published As

Publication number Publication date
GB9323632D0 (en) 1994-01-05
GB2283971B (en) 1997-11-26
GB9423015D0 (en) 1995-01-04

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PCNP Patent ceased through non-payment of renewal fee

Effective date: 20001115