Reaction of Hexachloroacetone with Activated Acetylenes in the Presence of N-Heterocycles. Synthesis of Trichloromethylated Bridgehead N-Heterocycles

Pyridine reacts smoothly with hexachloroacetone (HCA) in the presence of dialkyl acetylenedicarboxylates or dibenzoylacetylene to produce indolizines. Under similar conditions, isoquinoline led to oxazino[2,3-a]isoquinolines and/or pyrrolo[2,1-a]isoquinolines. Dimethyl 3,3-bis(trichloromethyl)-3H,4aH-[1,3]oxazino[2,3-a]quinoline-1,2-dicarboxylate or dimethyl 1-methyl-7-(2,2,2-tri­chloroacetyl)-1H-pyrrolo[1,2-a]imidazole-5,6-dicarboxylate was obtained from the reaction of quinoline or N-methylimidazole with dimethyl acetylenedicarboxylate in the presence of HCA.