Chloroalkylation of Unactivated Alkenes via a Cobalt-Mediated Radical Ligand Transfer (RLT) Photoredox Catalysis Platform

The development of modular difunctionalization strategies for unsaturated hydrocarbons is of particular interest, as it enables access to complex building blocks in a single step. Although great progress has been recently achieved in this field, difunctionalization of simple, nonconjugated alkenes represents a substantial challenge. Inspired by the radical rebound paradigm found in metalloenzymes, radical ligand transfer (RLT) catalysis has recently emerged as a powerful and broadly applicable strategy for the selective functionalization of alkyl radicals. Here, we present our advancements on the metallaphotoredox platform, which leverages the efficient cooperation between photoredox and cobalt RLT catalysis. A variety of electrophilic, functionalized carbon-centered radicals can be generated and efficiently incorporated into alkene derivatives, while the resulting nucleophilic radicals are further harnessed through homolytic substitution at a cobalt-bound ligand, enabling controlled transfer of a halogen nucleophile. The method accommodates a wide variety of radical precursors and exhibits excellent functional group tolerance, enabling efficient access to chloroalkyl derivatives. An integrated approach combining experimental and density functional theory studies revealed fundamental aspects of cobalt-mediated RLT and provided a plausible explanation for the key roles of the silver carbonate additive.