Addition reactions of heterocyclic compounds. Part 67. Products from 1-phenylbut-1-yn-3-one with various heterocycles, and from dimethyl acetylenedicarboxylate with some 2-substituted pyridines

Abstract

1-Phenylbut-1-yn-3-one was dimerised by 1-alkylpyrroles but with furan gave a 1 : 2 molar adduct. With 3-methylpyridine and quinoline it yielded dihydro-H-quinolizinones, with benzimidazole Michael addition at nitrogen occurred, but with N-alkylbenzimidazoles ring expansion to 1,6-benzodiazocin-2(1H)-ones took place. Dimethyl acetylenedicarboxylate with 1-(2-pyridyl)-butan-2-one gave a tricyclic quinolizine while quinolizines, azepines and indolizines were obtained from other pyridines. The structures of the products were deduced from their ¹H, ¹³C n.m.r., and other spectra.