“Tandem” reactivity of 2-Cyano-Δ3-piperideines II: Endocyclic versus exocyclic iminium ion reactions

Abstract The C-7 substituted 2-cyano-Δ 3 -piperideine 2 reacts regioselectively with indole to give a 2/1 mixture of 4-(3-indolyl)piperidines 11 which were converted in four steps to the tetrahydropyridocarbazole derivative 16 .