Visible-light-induced synthesis of bibenzofuranones via a cerium-mediated energy transfer process

Benzofuran-3(2H)-one compounds are important bioactive molecules. Synthesis of bibenzofuranones from benzils via a radical cyclization-dimerization tandem process, efficiently constructing the C-O/C-C bonds and contiguous quaternary carbon centers in a single step was reported. This reaction exhibits high regioselectivity, affording bibenzofuranones in moderate to excellent yields under mild conditions. Mechanistic studies suggest that cerium sulfate serves as both an energy transfer reagent and an oxidant in this process.