An Unexpected NH4HSO4-Catalyzed C3-H Alkenylation of Quinoxalin-2(1H)-ones with Allenes

Abstract

A novel and unexpected NH4HSO4-catalyzed C3–H alkenylation of quinoxalin-2(1H)-ones with allenes is described. This protocol offers a practical approach to a diverse array of 3-vinylquinoxalines in moderate to good yields with high regio- and stereoselectivity. The reaction is proposed to proceed via a nucleophilic addition pathway, in which NH4HSO4 may play a dual role by activating the quinoxalinone substrate and facilitating the generation of an alkenyl nucleophile from the allene. Gram-scale synthesis and representative derivatization reactions further highlight the synthetic utility of this method.