IMPROVED PROCESS FOR RIMONABANT

摘要

The present invention provides an improved and commercially viable process for the preparation of rimonabant substantially free of amide impurity, namely 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl-4-methyl-pyrazole-3-carboxamide and its pharmaceutically acceptable acid addition salts thereof. Thus, for example, 5-(4-chlorophenyl)-1-(2,4-dichlorophenyl-4-methyl-pyrazole-3-carboxylic acid chloride is reacted with 1-minopiperidine in the presence of a base and optionally using a phase transfer catalyst such as tetra-butylammonium bromide in a biphasic reaction medium containing water and a water-immiscible solvent to obtain pure rimonabant.