Site-Selective Access to Functionalized Pyrroloquinoxalinones via H-Atom Transfer from N═Csp2–H Bonds of Quinoxalinones

Abstract

Site-selective hydrogen atom transfer (HAT) from the N═C_sp²–H bonds of quinoxaline-2(1H)-ones is a highly attractive but underdeveloped domain. Reported herein is a highly selective, practical, and economically efficient approach for facile assembly of pyrroloquinoxalinones by synergistic photocatalysis and HAT catalysis. The reaction proceeds through bromine radical-mediated HAT of quinoxalinones and imine radical addition to α-cyano-α,β-unsaturated ketones that establishes a cross-coupling/annulation cascade process, resulting in the synthesis of a series of functionalized pyrroloquinoxalinones. This protocol does not require transition metals or excess oxidants and uses easy-to-synthesize starting materials with excellent scalability and broad substrate scope. The establishment of N═C_sp² radical chemistry illustrates great potential for the synthesis of imine-containing molecules that are not possible with some traditional methods.