METHOD FOR CONVERSION OF CIS-TRANS-MIXTURE OF SUBSTITUTED BENZYLIDENEAMINES TO PURE CIS-ISOMER Russian patent published in 2007 - IPC C07C251/24 C07C249/14 C07B55/00 

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to a method for preparing pure cis-isomer from mixture of cis-trans-isomers of the formula (I): wherein Ar represents phenyl or naphthyl optionally mono- or disubstituted with (C₁-C₅)-alkyl, (C₁-C₅)-alkoxy-group, halogen atom, trifluoromethyl, ester or amido-group; R represents (C₁-C₅)-alkyl wherein indicated formula (I) comprises chiral C₁-carbon atom and adjacent chiral C₂-carbon atom, and wherein C₂-atom is added to hydrogen atom and to strong electron-acceptor group G chosen from group including nitro-, nitroso-group, nitrile, cyanato-, isocyanato-group, nitro-substituted aryl, sulfonyl and carbonyl, and wherein at least one atom or group added to C₁-atom distinct from atoms or groups added to C₂-atom that can be used as intermediate compound in synthesis of cis-isomers of benzamide-piperidine compounds eliciting activity as antagonists of NK-1 receptors. Method involves steps for dispersing a mixture of cis- and trans-isomers of the formula (I) in inert solvent medium wherein indicated cis-isomer is essentially less soluble as compared with indicated trans-isomer followed by heating indicated dispersion to complete dissolving indicated trans-isomer and dissolving at least 10 wt.-% of cis-isomer, maintaining indicated heating step for providing possibility for mutual conversion of indicated cis- and trans-isomers, cooling the indicated mixture providing crystallization of cis-isomer and separation of indicated crystalline cis-isomer from indicated solvent.

EFFECT: improved method of conversion.

9 cl, 1 tbl, 4 sch, 1 dwg, 5 ex