Horner-Wadsworth-Emmons Reagents as Azomethine Ylide Analogues: Pyrrole Synthesis via (3+2) Cycloaddition

Amido-substituted Horner-Wadsworth-Emmons reagents can serve as precursors to 1,3-dipoles for use in cycloaddition. These compounds are assembled in one pot via the TMSOTf-catalyzed Arbuzov reaction of imines, acid chlorides, and phosphites. The coupling of this synthesis with alkyne cycloaddition provides a three-component synthesis of pyrroles. The dipoles can be prepared with a diverse range of imines and acid chlorides, and (3 + 2) cycloaddition with unsymmetrical alkynes is highly regiospecific, providing a modular approach to form substituted pyrroles.