PROCESS FOR PREPARATION OF CRYSTALLINE FORM A OF PIMOBENDAN

摘要

The invention relates to the process of obtaining pimobendan. A method is proposed for the preparation of pimobendan polymorphous crystalline form A, comprising following steps:(i) dissolution of pimobendan in a polar solvent at a temperature close to the boiling point of the solvent, adding hot water in small portions, holding at temperature about 60 centigrade, cooling of the solution up to ambient temperature, isolation of crystals, washing them with acetone and drying thereof, therefore yielding pimobendan monohydrate;(ii) suspension of pimobendan monohydrate obtained in step (i) in simmering aprotic polar solvent;(iii) cooling of the suspension obtained in step (i) up to ambient temperature, filtration, washing with acetone, drying and isolation of pimobendan crystalline form A.