Light-switchable divergent C–H activation and cross-coupling of cyclic ethers with aromatic aldehydes

Divergent coupling reactions of cyclic ethers provide a powerful strategy for accessing high-value small molecules. We report a metal-free, light-regulated divergent method for C-H functionalization of cyclic ethers with aromatic aldehydes that selectively yields either hydroxyarylation or cross-dehydrogenative coupling products. Using <i>tert</i>-butyl peroxybenzoate as an oxidant and cyclic ether as both the solvent and the reductant, the reaction proceeds <i>via</i> a condition-dependent radical/ionic mechanism. This strategy enables sustainable access to diverse cyclic ether derivatives for medicinal and materials applications.