Process for the preparation of high purity buspiron and the hydrochloride thereof

Process for the preparation of 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-butyl]-8-aza-spiro[4.5]decane-7 ,9-dione (buspiron) of the Formula I ##STR6## and the hydrochlorides thereof having high purity by subjecting 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-but-2-inyl]-8-aza-spiro[4.5]dec ane-7,9-dione of the Formula II ##STR7## to catalytic hydrogenation in the presence of a palladium or Raney-nickel catalyst in an inert organic solvent and optionally converting the 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-butyl]-8-aza-spiro[4.5]decane-7 ,9-dione thus obtained into the hydrochloride thereof which comprises continuously adding a solution of 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-but-2-inyl]-8-aza-spiro[4.5]dec ane-7,9-dione formed with an inert organic solvent having a concentration of a least 40% by weight to a suspension of a catalyst in an inert organic solvent, removing the catalyst and subsequently

• a) isolating the 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-butyl]-8-aza-spiro[4.5]decane-7 ,9-dione base, and/or
• b) treating the 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-butyl]-8-aza-spiro[4.5]decane-7 ,9-dione base with hydrogen chloride in ethanol or isopropanol under stirring at a temperature between 15.degree. C. and 40.degree. C. and isolating the 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-butyl]-8-aza-spiro[4.5]decane-7 ,9-dione hydrochloride melting at 188.degree.-191.degree. C., or
• c) treating the 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-butyl]-8-aza-spiro[4.5]decane-7 ,9-dione base with hydrogen chloride in ethyl acetate or isopropanol at a temperature not exceeding 70.degree. C. under stirring and isolating the 8-[4-[4-(pyrimidine-2-yl)-piperazine-1-yl]-butyl]-8-aza-spiro[4.5]decane-7 ,9-dione hydrochloride melting at 201.degree.-203.degree. C.