Patent ID: 6878848
Filing Date: 2005-04-12
Classification: C07B,C07C

Abstract:
1. A process for preparing a pure cis isomer from a mixture of cis-trans isomers of formula wherein Ar is phenyl or naphthyl optionally mono- or disubstituted by C 1-5 alkyl, C 1-5 alkoxy, halogen, trifluoromethyl, ester or amido; and R is C 1-5 alkyl; wherein X is a strongly electron withdrawing moiety selected from the group consisting of nitro, nitroso, nitrilo, isocyanato, sulfonyl, carbonyl and nitro substituted aryl; comprising the steps of: a. dispersing a mixture of cis and trans isomers of formula I in an inert solvent wherein said cis isomer is substantially less soluble than said trans isomer; b. heating said dispersion to completely dissolve said trans isomer and to dissolve at least 10% by weight of the cis isomers; c. maintaining said heating step to allow interconversion of said cis and trans isomers; d. cooling said mixture thereby crystallizing the cis isomer; and e. separating said crystalline cis isomer from said solvent.