Synthesis of N-Ureido Pyrrole Derivatives Through Gold-Catalysed Reaction: Solvent and Catalyst Effect

Abstract

Substituted pyrroles were obtained as a result of metal-catalyzed cyclization of alpha propargyl acetophenone and alpha-propargyl-beta-ketoesters with semicarbazide. Optimum conditions and general procedures with high yields were established in a single pot. Eleven different N-ureido-pyrrole derivatives were successfully yielded. Different ynone derivatives having various functionalities did not affect the cyclization reaction but except a slight decrease in product yield. Screening of optimum catalyst revealed that gold(III) chloride was the best catalyst for the cyclization reaction. We believe that this is the first time an N-ureido-pyrrole skeleton starting from ynone has been synthesized in the literature. Unconjugated ynone derivatives, which hold several functional groups, are subjected to reaction with semicarbazide in the presence of Gold (III) chloride catalyst. In consequence of the reactions, the synthesis of eleven different N-ureido pyrrole derivatives, which contain amide group attached to the nitrogen atom in the pyrrole ring, will take place. image