Visible-light photocatalyzed radical dipolar annulations for diastereoselective synthesis of pyrrolo[2,1-a] isoquinoline-fused benzosulfolane skeletons

Abstract

We report a visible-light photocatalyzed stereoselective radical 1,3-dipolar cycloaddition between benzo[b]thiophene sulfones and tetrahydroisoquinolines, providing an approach for the concise synthesis of pseudo-natural inspired fused pentacyclic skeletons. Using this protocol, a diverse range of valuable pyrrolo[2,1-a]isoquinoline-fused benzosulfolanes were rapidly synthesised in moderate to good yields and excellent diastereoselectivities. Mechanistic investigations including radical control experiments and light on/off studies suggest that the reaction underwent a visible-light induced radical pathway. The insights gained from our studies are expected to advance general efforts towards the green and efficient synthesis of biologically-oriented pseudo-natural products and privileged heterocyclic skeletons.