Visible light photoredox catalysis with N-hydroxyphthalimide for [4+2] cyclization between N-methylanilines and maleimides

An efficient [4+2] cyclization of N-methylanilines with maleimides to afford tetrahydroquinolines using N-hydroxyphthalimide as a metal-free and cheap organophotoredox catalyst is reported. The protocol involves C(sp(3))-H activation of N-methylanilines for the formation of alpha-amino radical without an oxidant at room temperature. The present method describes an easy preparation of tricyclic heterocycles in good to excellent yields under mild reaction conditions. 2016 Elsevier Ltd. All rights reserved.