Chlorproethazine can be synthesized from a diphenylsulfidederivative. The general scheme is sufficiently flexible to permit the interchange of the order of some of the steps.
Thus alkylation of 2-(2-bromo-phenylsulfanyl)-5-chloro-aniline [105790-02-1] (1) with 3-chloro-1-diethylaminopropane [104-77-8] (2) leads to the intermediate (3). Ring closure as above by nucleophilic aromatic displacement leads to the antipsychotic drug chlorproethazine (4).