BigPatents India

The present invention provides a process of preparing Risperidone which comprises: i) reacting 3-(2-chloroethyl)-6, 7,8,9-tetrahydro-2-methyl-4H-pyrido-(1,2- a]pyrimidin-4-one (Compound II) with 4-(2,4-difluorobenzoyl)piperidine oxime (Compound III) using a base and catalyst in a solvent selected from a group consisting of acetonitrile, N,N-dimethylformamide and methyl isobutyl ketone at a temperature in the range of75-110°C to form oxime (Compound IV) and ii) in situ cyclization of oxime (Compound IV) to form Risperidone, which is further purified by crystallization.