Triazolopyridines. Part 12: A New Synthesis of Indolizines from Triazolopyridine Ylides

Abstract

Treatment of 2-acylmethyl-1.2.3-triazoloIl.5-a]pyridiniumylides (1) with methyl propiolate in non-polar solvent gives good yfelds of 1.2.3-trisubstituted indolizines (5).A mechanism for the transformation is suggested.We have recently reported1 that ylides of general type 11) derived from 2-acylmethyl-1.2.3-triazolo[1.5-alpyridinesreact with acetylenic esters in acetonitrile to give new ylides of type ( 2) and (3).We have further reported 2 that a change in the reaction of the ylides with dimethyl acetylenedicarboxylate (DMAD) gives rise to