Patent ID: 8436182

Claim:
A process for the preparation of solifenacin and/or pharmaceutically acceptable salt or salts thereof of high pharmaceutical purity, comprising, reacting (S)-1-phenyl-1,2,3,4-tetrahydroisoquinoline with triphosgene in the presence of a tertiary aromatic amine, in an aromatic hydrocarbon to form a reaction mixture, evaporating said reaction mixture, treating the evaporated reaction mixture with a non-polar aprotic solvent at reflux, crystallizing the treated evaporated reaction mixture at 5-15° C., isolating (S)-1-phenyl-1,2,3,4-tetrahydroisoquinolinecarbonyl chloride as crystalline solid of at least 98% purity, dissolving said crystalline solid in a polar aprotic solvent, and adding said crystalline solid in polar aprotic solvent to a suspension generated in situ of (R)-3-quinuclidinoloxy anion in the same polar aprotic solvent to acylate the (R)-3-quinuclidinoloxy anion and form solifenacin base.