Patent ID: 8063217
Filing Date: 2011-11-22
Classification: C07D

Abstract:
1. A process for preparation of Methyl-(+)-(S)-alpha-(2-chlorophenyl)-6,7-dihydrothieno[3,2-c]pyridine-5(4H)-acetic acid methyl ester as free base [S(+)clopidogrel free base] of Formula-I, comprising following steps: a) reacting an aqueous solution of a S(+)enantiomer of compound of Formula-II as hydrochloride salt with paraformaldehyde and catalytic amount of hydrochloric acid; b) heating the reaction mixture of step a); c) separating out the aqueous layer from the sticky mass; d) extracting the S(+)clopidogrel free base from the aqueous layer obtained in step c) with petroleum ether or hexane while maintaining the pH varying between 2 to 3; e) repeating the step d) while maintaining the said pH varying between 2 to 3 of the aqueous layer; and f) concentrating the combined organic layers obtained in steps d) and e) to result in S(+)clopidogrel free base in chemical purity, as checked by Gas Chromatography, of 99.5% or more and yield of 80% or more.