Reaction of 3-Thioformylindolizines with Tributylphosphine

2-Phenyl-3-thioformylindolizine and 1,2-dimethyl-3-thioformylindolizine undergo a novel desulfur coupling reaction in the presence of tributylphosphine to give (E)-1,2-bis(3-indolizinyl)ethenes in high yields. The structures of products were confirmed by IR, 1H NMR, MS, elemental analysis and single crystal X-ray diffraction analysis. The mechanisms involved in various stages of the reaction were discussed.