Oxidative Cyclization of 2-Aryl-3-arylamino-2-alkenenitriles to N-Arylindole-3-carbonitriles Mediated by NXS/Zn(OAc)2

A variety of 2-aryl-3-arylamino-2-alkenenitriles were converted to N-arylindole-3-carbonitriles in a one-pot manner through NBS- or NCS-mediated halogenation followed by Zn(OAc)(2)-catalyzed intramolecular cyclization. It is postulated that the process involves the formation of arylnitrenium ion intermediates, which undergo the electrophilic aromatic substitution to give the cyclized N-arylindole product.