Efficient Synthesis of Medium‐sized Nitrogen Heterocycles by Brønsted Acid‐Catalyzed Cyclization of Ene‐ynamides

Abstract

A Brønsted acid‐catalysed cyclization of ene‐ynamides has been developed to construct 7‐ or 8‐membered azacycles in good to high yields. The use of a simple C=C double bond as a nucleophile enables the synthesis of medium‐sized ring from an acyclic ynamide. This reaction system features simple and mild reaction conditions without any metal catalysts, and no requirement of high dilution for medium‐sized ring formation. This method is applicable to a variety of substituents on the ynamides, such as alkyl, aryl, acetylene and silyloxy group.