Synthesis of Enamides by Ruthenium-Catalyzed Reaction of Alkyl Azides with Acid Anhydrides in Ionic Liquid

Enamides were synthesized by a ruthenium-catalyzed one-pot, one-step procedure from alkyl azides and acid anhydrides. The substrate scope includes not only secondary azides, but also primary aliphatic ones to give a wide range of enamides containing various functional groups. This one-step procedure was based on the newly discovered activity of Severin's diruthenium complex ([Cp boolean AND RuCl2](2): Cp boolean AND=(5)-1-methoxy-2,4-di-tert-butyl-3-neopentylcyclopentadienyl) for the transformation of alkyl azides into the corresponding N-H imine intermediates in ionic liquids. The formation of ruthenium tetrazene complexes was observed in the stoichiometric reaction of Severin's complex with alkyl azides, which acted as the catalyst for the formation of N-H imine intermediates.