Sonogashira Reaction of the Indolizine Ring

2-tert-Butyl-5-iodoindolizine underwent Sonogashira reaction with acetylenes in the presence of dichlorobis(triphenylphosphine)palladium, copper(I) iodide, and triethylamine in acetonitrile to give to the corresponding 5-ethynylindolizines in high yields; 5-iodo-2-phenylindolizine and 5-bromo-2-tert-butylindolizine did not undergo the reaction. Several structures were characterized by X-ray. The 5-ethynylindolizines did not undergo cyclization to give cycl[3.2.2]azines.