[3+2]Cycloaddition of Propargylamines and α-Acylketene Dithioacetals: A Synthetic Strategy for Highly Substituted Pyrroles

A new [3+2]?cycloaddition strategy for the direct synthesis of highly substituted pyrroles from the readily available a-acylketene dithioacetals (or related substrates) and commercially available propargylamines under mild metal-free conditions has been developed. In this reaction, the acyl group plays a critical role in driving the conjugate addition of propargylamine and further cyclization to give pyrroles. Furthermore, the wide scope was confirmed by the preparation of 1,2,3,4-tetrasubstituted pyrroles (6070% yields) via a formal 1,2-acyl migrating [3+2]?cycloaddition pathway with N-methylprop-2-yn-1-amine as the secondary amine component.