Potential metabolites of the neuroleptic agent chlorprothixene; synthesis and pharmacology of the 3-, 4-, 6- and 7-hydroxy and methoxy derivatives of 2-chloro-9-(3-dimethylaminopropylidene)-thioxanthenes

Abstract

Cyclization of the acids IV-VII with sulfuric or polyphosphoric acid resulted in the thioxanthones VIIIa-d which were treated with 3-dimethylaminopropylmagnesium chloride and gave the amino alcohols Xa-d. Their acid catalyzed dehydrations afforded the methoxy derivatives of chlorprothixene IIIa-d, mostly in form of mixtures of geometric isomers. Whereas the results of attempts to demethylate these products with boron tribromide gave mostly unsatisfactory results, the demethylation with pyridine hydrochloride at 190-200 °C was successful; alcohols X were the most suitable starting materials. In this manner, the hydroxy derivatives of chloroprothixene IIa-d were obtained, mostly as pure geometric isomers. The configuration was assigned on the basis of their IR spectra. Z-Isomers are potential metabolites of the neuroleptic agent chlorprothixene (I). Compounds II and III are little toxic, have low central depressant activity and are inactive cataleptically.