The Reaction of N -Isocyaniminotriphenylphosphorane With Biacetyl in the Presence of (E) -Cinnamic Acids: Synthesis of Fully Substituted 1,3,4-Oxadiazole Derivatives via Intramolecular AZA -Wittig Reactions of in Situ Generated Iminophosphoranes

Reaction of N-isocyaniminotriphenylphosphorane with biacetyl in the presence of (E)-cinnamic acids proceeds smoothly at room temperature and under neutral conditions to afford sterically congested 1,3,4-oxadiazole derivatives in high yields. The reaction proceeds smoothly and straightforward under mild conditions and no side reactions are observed.