Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C45/00—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds
  • C07C45/45—Preparation of compounds having >C = O groups bound only to carbon or hydrogen atoms; Preparation of chelates of such compounds by condensation

Definitions

• the present invention relates to one step process for synthesis of ⁇ , ⁇ - unsaturated ketones from aldehydes and compounds containing allylic carbons.
• the present invention provides Pd/N-Heterocyclic carbene catalyzed synthesis of /?,y-unsaturated ketones.
• acylzirconocene chloride Hanzawa, Y.; Tabuchi, N.; Taguchi, T. Tetrahedron Lett. 1998, 39, 6249
• chromium carbene complexes Sakurai, H.; Tanabe, K.; Narasaka, K. Chem. Lett. 1999, 309
• these reactions results in acylation products as a mixture of regioisomers, which are difficult to separate.
• the main objective of the present invention is to provide one step process for synthesis of / ⁇ -unsaturated ketones from aldehydes and compounds containing allylic carbons.
• Another objective of the present invention is to provide Pd/N-Heterocyclic carbene catalyzed synthesis of /?,y-unsaturated ketones.
• the present invention provides one step ' process for preparation of /?,y-unsaturated carbonyl compounds/unsymmetrical ketones (IV) comprising adding solution of an aldehyde (II) to a solution of Pd-complex, jV-Heterocyclic carbenes (NHC) (III), a base and activated allylic carbon compound (I) in an organic solvent maintained at 0°C further raising the reaction mixture to room temperature ranging between 20-35 °C followed by stirring for a period ranging between 5-24 h to obtain / ⁇ -unsaturated carbonyl compounds/unsymmetrical ketones (IV);
• R represent -H, aromatics, heteroaromatics, cyclic, heterocyclic, alkenes, alkyls, alkynes etc.
• X represent halogens, -OH, -OTs, -OMs, carbonates, acetates etc.
• R 4 and R 5 can be -H
• representative compounds of ⁇ , ⁇ - unsaturated carbonyl compounds/unsymmetrical ketones of formula (IV) are:
• the Pd complex is selected from Pd(PPh 3 ) 4 , Pd(OAc) 2 , PdCl 2 (PPh 3 ) 2 , Pd 2 (dba) 3 , PdCl 2 (PPh 3 ) 2 ferro, PdCl 2 .
• N-Heterocyclic carbenes are selected from,
• the base is selected from organic or inorganic bases either alone or in combination thereof.
• the organic base is selected from DBU, DABCO, TMEDA, 1-Methylpiperazine, DMAP, DIPEA, Pyridine, NaOAc, Et 3 N, ammonia and the inorganic base is selected from alkali and alkaline earth metal hydroxides, carbonates, bicarbonates either alone or in combination thereof.
• inorganic base is selected from the group consisting of K 2 C0 3 , Cs 2 C0 3 Ag 2 C0 3 , K 3 P0 4 and MgS0 4 .
• the solvents are selected from polar and non-polar solvents selected from alcohols, hydrocarbons, chlorinated hydrocarbons, ethers, cyclic ethers, nitriles either alone or in combination thereof.
• - solvent used is acetonitrile.
• yield of ?,y-unsaturated carbonyl compounds/unsymmetrical ketones (IV) is in the range of 46-73%.
• Fig 1 a show 1H NMR of compound 1.
• Fig lb show 13 C NMR of compound 1.
• Fig lc show DEPT spectra of compound 1.
• the present invention provides hitherto unexplored N-heterocyclic Carbene (NHC) mediated acylation of activated allylic carbons with aldehydes in presence of Palladium-complex to provide value added corresponding /?,y-unsaturated carbonyl compounds/unsymmetrical ketones.
• NHC N-heterocyclic Carbene
• the invention disclose Pd/NHC- catalyzed one step process for preparation of ⁇ -unsaturated carbonyl compounds/unsymmetrical ketones comprising adding solution of an aldehyde (II) to a solution of Pd-complex, NHC (III), a base and activated allylic carbon compound (I) in an organic solvent maintained at 0°C; raising the reaction mixture to room temperature followed by stirring at room temperature to obtain desired compound (IV); as shown in scheme 3.
• R 1 , R 2 -H, aromatics, heteroaromatics, cyclic, heterocyclic , alkenes, alkyl; alkynes etc.
• X halogens, -OH, -OTs, -OMs, carbonates, acetates etc.
• R 4 and R 5 can be -H
• the Pd catalyst is selected from but not limited to Pd(PPh 3 ) 4 , Pd(OAc);
• -heterocyclic carbenes are selected from but not limited to;
• the base is selected from organic bases such as DBU, DABCO, TMEDA, 1- Methylpiperazine, DMAP, DIPEA, Pyridine, NaOAc, Et 3 N, ammonia and the like;
• the inorganic base may be selected from alkali and alkaline earth metal hydroxides, carbonates, bicarbonates such as K 2 C0 3 , Cs 2 C0 3 Ag 2 C0 3 , K 3 P0 4 and the like either alone or in combination thereof.
• the solvent for purpose of the invention may be selected from polar and non- polar solvents such as alcohols, hydrocarbons, chlorinated hydrocarbons, ethers, cyclic ethers, nitriles and the like either alone or in combination thereof.
• polar and non- polar solvents such as alcohols, hydrocarbons, chlorinated hydrocarbons, ethers, cyclic ethers, nitriles and the like either alone or in combination thereof.
• the present invention provide corresponding ⁇ , ⁇ - unsaturated ketones in good to moderate yields using various allylic carbon compounds and aldehydes as shown in Table 1.
• compound 8 is prepared (Scheme 4) by treating allyl carbonate with a solution of Pd(PPh 3 ) 4 in an organic solvent with stirring at 0 °C followed by sequential addition of NHC's salt, 4-(phenylsulfonyl)benzaldehyde in presence of an organic base. After stirring for 12 h at room temperature the reaction mixture is concentrated; loaded on silica gel column and purified by using solvent gradient of Pet Ether: Ethyl Acetate (1 :9) to yield desired compound 8, (E)-4-(furan-3- yl)-l -(4-(phenylsulfonyl)phenyl)but-3-en-l-one as colorless oil.
• the compound may optionally be purified from suitable crystallization solvent(s) if it is solid.
• ⁇ -unsaturated are used for the synthesis of fine chemicals and other complex structures.
• reaction mixture After stirring for 12 h at room temperature the reaction mixture was filtered through a pad of celite, and the solvent was removed under reduced pressure. The crude reaction mixture was directly loaded on silica gel column and purified by using solvent gradient of Pet Ether: Ethyl Acetate (1 :9) to yield desired compound as colorless oil (21 mg, 73 %).

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Cited By (7)

• 2013
  • 2013-09-06 WO PCT/IN2013/000541 patent/WO2014037963A1/fr not_active Ceased

Non-Patent Citations (5)

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