Bismuth-photocatalysed Heck-type coupling with alkyl and aryl electrophiles

The Heck reaction, which is widely used for the construction of C‒C bonds, is a cornerstone of modern organic synthesis. Traditionally, this transformation relies on transition metal catalysts, whose frontier <i>d</i>-orbitals cement the mechanism and scope of the reaction. Here we present a conceptually distinct Heck-type coupling strategy that replaces transition metals with a photoactive bismuth complex, marking an advance in main group catalysis. This approach leverages the distinctive electronic and photophysical properties of bismuth, providing a reimagined reaction pathway. The bismuth catalyst undergoes a photo-induced ligand-to-metal charge transfer processes, unmasking a Bi(II) species capable of halogen atom transfer (XAT) processes with alkyl iodides. The multifaceted redox-dependent photophysical properties of the bismuth catalyst facilitate the coupling of aryl and alkyl electrophiles with styrenes through an intricate interplay of mechanistic steps. The method provides a mechanistic blueprint for accessing coveted Bi(II) species, offering an alternative to transition metal catalysis in organic synthesis.