Synthesis and reactivity of (1S)-N-(1-phenylethyl)maleimide towards nucleophiles: an application to preparation of chiral pyrroloisothiochroman and pyrrolobenzo[d]thiepine based on π-cationic cyclization

Chiral pyrroloisothiochroman and pyrrolo[d]thiepine were obtained efficiently in four steps from N-alkylated maleimides via, successively, sulfurization, regioselective reduction followed by π-cationic cyclization of the N-acyliminium ion intermediates. These latter, in addition, led to conjugate enamides as a consequence of the dehydration reaction.