A New Strategy for the Synthesis of 4-Propargyl-Substituted 1H-Pyrroles from N-(5-phenyl-2,4-pentadiynyl) beta-Enaminones

A new method for the synthesis of 4-propargyl-substituted 1H-pyrroles is described. When treated with sodium hydride in refluxing dichloromethane, N-(5-phenyl-2,4-pentadiynyl) beta-enaminones, synthesized by the coupling of N-propargylic beta-enaminones with phenylacetylene, afforded 4-propargyl-substituted pyrrole derivatives. This conversion was general for a variety of N-(5-phenyl-2,4-pentadiynyl) beta-enaminones and displayed broad functional group tolerance. During the reaction, not only cyclization of linear precursors to pyrrole ring takes place, but also propargyl group is introduced to pyrrole core in one-pot. The enrichment of pyrrole compounds with a propargyl unit might exhibit potential for the synthesis of heterocyclic molecules of pharmacological interest.