Stepwise Carbene Transfer Reaction with Alkenes beyond Cyclopropanation

Abstract Metal carbene transfer reactions have been well-established as an indispensable tool in modern organic synthesis, especially in the construction of C–C and C–X bonds with high efficiency and selectivity. Among these, stepwise carbene transfer reaction with alkenes beyond classical cyclopropanation reaction has been demonstrated as a practical method for the effective olefinic C–H/C–C bond functionalization. This review highlights the recent achievements in this area for the direct C–C bond formation involving metal carbene species with alkenes through a through stepwise reaction pathway. The content of this review is organized into three general categories according to the types of the reactions, including (i) direct nucleophilic addition of alkenes with metal carbene species, (ii) cross-coupling reaction via an alkenylic C–H bond activation and migration insertion sequence, and (iii) catalytic coupling reaction involving radical intermediate. Considering this rapidly evolving field, detailed reaction mechanism, current limitations, and future research directions are discussed. 1 Introduction 2 Nucleophilic Addition of Alkenes to Metal Carbene Species 2.1 Using Polarized Alkenes 2.2 Using Unactivated Alkenes 2.3 Cascade Reactions 3 Cross-Coupling Reaction Involving Metal Carbene Migratory Insertion Process 4 Coupling Reaction Involving Radical Intermediate 5 Conclusions and Perspectives