Efficient synthesis of antihistamines clocinizine and chlorcyclizine

A simple and efficient route has been developed for the synthesis of anti-histamine drugs clocinizine and chlorcyclizine. The common intermediate 1-[(4-chloro phenyl) (phenyl)-methyl]-piperazine (8), is prepared from (4-chlorophenyl) (phenyl)-methanone (5), in three steps with excellent yields. All the reactions proceeded smoothly and the products were also isolated easily.