Exploiting the Nucleophilicity of N-H Imines: Synthesis of Enamides from Alkyl Azides and Acid Anhydrides

The nucleophilicity of N-unsubstituted imines, which were generated from alkyl azides by a ruthenium-catalyzed reaction, was investigated in the reaction with acid anhydrides. The initial products were N-acylimines, which isomerized to the corresponding enamides. Heating or triethylamine facilitated the isomerization of N-acylimines that are stable at room temperature. A wide range of acyclic and cyclic enamides containing various functional groups was successfully synthesized under mild conditions. In addition to acetic anhydride, various acid anhydrides were applicable. From the reaction with cyclic anhydrides, enamides containing carboxylic acid group were obtained.