[3 + 2] radical sulfuration of alkenes by organic photocatalysis

Abstract

The C–S bond is one of the most fundamental chemical bonds in synthetic chemistry. However, how to control the highly reactive thiyl radical and develop new strategies for forming C–S bonds remains a challenging yet elusive objective. Herein, we demonstrate that a triple radical catalytic cycle, specifically the combination of organic photocatalysis, hydrogen atom transfer (HAT) catalysis and a programmed radical relay cycle, can be leveraged to enable the [3 + 2] radical sulfuration of alkenes by carrying out multi-component radical cross-coupling. CS₂ is a masked 1,3-disulfur radical equivalent, successfully leading to five-membered-ring sulfur-containing scaffolds with six C–S bonds. This visible-light-mediated organic photocatalytic mechanism can allow multiple reactive radicals to be used programmatically. Applying this strategy enables us to find new methods for forming chemical bonds that had previously been inaccessible or uninvestigated.