Pyrrolyl-radical-based di-/tri-functionalization of alkenes using sulfonyl pyrroles via radical/radical cross-coupling

Abstract

Installation of a pyrrolyl group on the position adjacent to an electron-withdrawing group presents significant challenges, as both electrophilic and radical addition to pyrroles suffer from some drawbacks. Here, a visible light-mediated radical/radical cross-coupling strategy has been developed using sulfonyl pyrrole as a novel precursor to both the sulfonyl and pyrrolyl radicals, enabling the efficient construction of dipyrrolyl acetonitriles and benzhydryl pyrroles. This success highlighted the utilization of a carbon-centered pyrrolyl radical derived from N–S bond activation in synthetic chemistry. This protocol broadens the transformations of sulfonamides and achieves multi-functionalization of alkenes to build quaternary carbon centers. Density functional theory (DFT) calculations demonstrated that energy transfer between the excited photocatalyst and sulfonyl pyrrole contributed to N–S bond cleavage and resulted in pyrrolylation.