Cascade cyclization for the synthesis of indolo[2,1-α]isoquinoline derivatives via visible-light-induced halogen-atom-transfer (XAT) and hydrogen-atom-transfer (HAT)

A transition metal-free photoredox cascade cyclization is herein reported. In this protocol, sustainable visible light was used as the energy source and organic light-emitting molecule eosin Y served as an efficient photocatalyst. A variety of easily available 2-aryl-N-acryloyl indoles can readily react with alkyl radicals, which are generated from organohalides and tertiary amines via either the halogen-atom-transfer (XAT) or the hydrogen-atom-transfer (HAT) process, furnishing the desired indolo[2,1-α]isoquinoline derivatives in good to moderate yields. This protocol features broad substrate scope and good functional group tolerance under mild conditions.