Efficient Radical‐Mediated Intermolecular α‐Alkylation Reactions of Carbonyl Compounds with Nonactivated Alkenes

Abstract Alkylation reactions are fundamental carbon‐carbon bond‐forming reactions in synthetic organic chemistry. Among them, intermolecular α‐alkylation reactions of carbonyl compounds with alkenes are important because they are more atom‐economical than the equivalent processes using alkyl halides. However, intermolecular reactions with nonactivated alkenes such as 1‐hexene, which can allow the use of a wide range of valuable substrates, have been considered to be very challenging for a long time. In this review, radical‐mediated intermolecular α‐alkylation reactions of carbonyl compounds with nonactivated alkenes are discussed. The examples are grouped into three types of reactions: peroxide‐mediated reactions, metal‐oxidant‐mediated reactions, and photoactivated reactions. Photoredox‐catalyzed alkylation reactions under visible‐light irradiation are discussed as a particularly promising recent hot topic. This review provides brief history and new prospects on the α‐alkylation process with nonactivated alkenes using α‐carbonyl radical species.