A General Photoredox Platform for Divergent Couplings of Alkenes with Aliphatic Carbonyls via Ligated Boryl Radicals

The activation of aliphatic carbonyls to form ketyl radicals for C–C bond construction remains a formidable challenge, primarily due to their highly negative reduction potentials. Conventional strategies typically rely on stoichiometric metal reductants or strongly reducing conditions. Herein, we disclose a general photoredox platform that leverages ligated boryl radicals to efficiently activate aliphatic carbonyls, thus enabling divergent hydroxyalkylation of alkenes under metal-free and mild conditions. Notably, this strategy accommodates a wide range of alkenes, including α-trifluoromethyl olefins, aliphatic olefins, heteroatom-substituted alkenes, styrenes, and electron-deficient alkenes. Furthermore, by fine-tuning the catalytic system, the coupling of α-CF3 alkenes with aliphatic carbonyls can be selectively directed toward either defluoroalkylation or hydroalkylation products with high chemoselectivity, highlighting the versatility and tunability of this approach. Mechanistic studies confirm the critical involvement of ligated boryl radicals in the carbonyl activation. The synthetic utility of this protocol is further demonstrated through late-stage functionalization of pharmaceutically relevant molecules. With its broad substrate scope, good functional group compatibility, and programmable selectivity, this method provides a general and practical strategy for functionalization of aliphatic carbonyls.