From Hydrogenation to Transfer Hydrogenation to Hydrogen Auto-Transfer in Enantioselective Metal-Catalyzed Carbonyl Reductive Coupling: Past, Present, and Future
Catherine G. Santana, Michael J. Krische
Abstract
Atom-efficient processes that occur via addition, redistribution, or removal of hydrogen underlie many large-volume industrial processes and pervade all segments of chemical industry. Although carbonyl addition is one of the oldest and most broadly utilized methods for C–C bond formation, the delivery of nonstabilized carbanions to carbonyl compounds has relied on premetalated reagents or metallic/organometallic reductants, which pose issues of safety and challenges vis-à-vis large-volume implementation. Catalytic carbonyl reductive couplings promoted via hydrogenation, transfer hydrogenation, and hydrogen autotransfer allow abundant unsaturated hydrocarbons to serve as substitutes to organometallic reagents, enabling C–C bond formation in the absence of stoichiometric metals. This Perspective (a) highlights past milestones in catalytic hydrogenation, hydrogen transfer, and hydrogen autotransfer; (b) summarizes current methods for catalytic enantioselective carbonyl reductive couplings; and (c) describes future opportunities based on the patterns of reactivity that animate transformations of this type.