Pyrrolyl radical-involved di-/tri-functionalization of alkenes by sulfonyl pyrroles via radical/radical cross-coupling

Abstract

Installation of a pyrrolyl group on the adjacent position of an electron-withdrawing group presents significant challenges, as either the electrophilic or radical addition to pyrrole is suffered from some drawbacks. Herein, by using the sulfonyl pyrrole as the novel precursor of sulfonyl radical and pyrrolyl radical, a visible light-mediated radical/radical cross-coupling strategy has been developed to construct dipyrrolyl acetonitriles and benzhydryl pyrroles in good efficiency. This success highlighted the utilization of carbon-centered pyrrolyl radical derived from N–S bond activation in synthetic chemistry. This protocol broadened the transformations of sulfonamides and achieved multi-functionalization of alkenes to build quaternary carbon centers. DFT calculation demonstrated that the energy transfer between the excited photocatalyst and sulfonyl pyrrole contributed to N–S bond cleavage and resulted in pyrrolylation.