A Convenient Synthesis of Centperazine, an Antifilarial Candidate Drug

7-Ethyl-octahydro-2-methyl-6H-pyrazino[1,2-c]pyrimidin-6-one (centperazine) (1), an antifilarial candidate drug, currently undergoing phase II clinical trials, has been synthesized by a more economically viable alternative route. Condensation of N,N′-dibenzylethylenediamine (2) with 3,4-dibromobutyronitrile (3) gives 2-(1,4-dibenzyl-2-piperazinyl)acetonitrile (4), which, on catalytic reduction, debenzylation, cyclocarbamation and N-alkylation yields the target molecule 1 in 10.1% overall yield.