Regio- and Stereoselective 1,4-(Hetero)arylalkylation of Isoprene by Photoredox Catalysis

Abstract

Selective difunctionalization of isoprene, a bulk chemical with annual production, remains a long-standing challenge, primarily due to competing 1,2-, 3,4-, 1,4-, and 4,1-additions and E:Z isomerism. We report a metal-free photoredox-catalyzed 1,4-arylalkylation via arene C–H functionalization that achieves exclusive regioselectivity and outstanding E:Z stereocontrol (>20:1). Using Mes-Acr+BF4– as an organic photocatalyst under visible light, the reaction accommodates various arenes and imines, affording functionalized isoprenes in synthetically useful yields. Mechanistic studies indicate sequential radical addition and cross-coupling of allylic and α-amino radicals. This protocol offers a direct and selective approach to 1,4-functionalized adducts.