Deoxygenative Transition-Metal-Promoted Reductive Coupling and Cross-Coupling of Alcohols and Epoxides

Abstract

Abstract The prospective utilization of abundant, CO2-neutral, renewable feedstocks is driving the discovery and development of new reactions that refunctionalize oxygen-rich substrates such as alcohols and polyols through C–O bond activation. In this review, we highlight the development of transition-metal-promoted reactions of renewable alcohols and epoxides that result in carbon–carbon bond-formation. These include reductive self-coupling reactions and cross-coupling reactions of alcohols with alkenes and arene derivatives. Early approaches to reductive couplings employed stoichiometric amounts of low-valent transition-metal reagents to form the corresponding hydrocarbon dimers. More recently, the use of redox-active transition-metal catalysts together with a reductant has enhanced the practical applications and scope of the reductive coupling of alcohols. Inclusion of other reaction partners with alcohols such as unsaturated hydrocarbons and main-group organometallics has further expanded the diversity of carbon skeletons accessible and the potential for applications in chemical synthesis. Catalytic reductive coupling and cross-coupling reactions of epoxides are also highlighted. Mechanistic insights into the means of C–O activation and C–C bond formation, where available, are also highlighted. 1 Introduction 2 Stoichiometric Reductive Coupling of Alcohols 3 Catalytic Reductive Coupling of Alcohols 3.1 Heterogeneous Catalysis 3.2 Homogeneous Catalysis 4 Reductive Cross-Coupling of Alcohols 4.1 Reductive Alkylation 4.2 Reductive Addition to Olefins 5 Epoxide Reductive Coupling Reactions 6 Conclusions and Future Directions