Synthesis of tetradeuterated buspirone

Two methods have been developed for the synthesis of tetradeuterated buspirone. Synthesis of the title compound was accomplished by the reaction of 1-(2-pyrimidinyl)piperazine-3,3,5,5-d4 or 1-(2-pyrimidinyl)-piperazine-2,2,3,3,-d4 with 8-(bromobutyl)-8-azaspiro[4.5]decane-7,9-dione in refluxing acetonitrile.