From Hydrogenation to Transfer Hydrogenation to Hydrogen Auto-Transfer in Enantioselective Metal-Catalyzed Carbonyl Reductive Coupling: Past, Present, and Future

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.

Understanding Halide Counterion Effects in Enantioselective Ruthenium-Catalyzed Carbonyl (α-Aryl)allylation: Alkynes as Latent Allenes and Trifluoroethanol-Enhanced Turnover in The Conversion of Ethanol to Higher Alcohols via Hydrogen Auto-transfer

“…The development of atom-efficient catalytic methods for the valorization of renewable feedstocks is a long-standing goal of chemical research . To this end, our laboratory has introduced a family of hydrogen auto-transfer (“borrowing hydrogen”) processes that convert lower alcohols to higher alcohols. , These reactions affect carbinol C−H functionalization and, hence, differ from Guerbet-type reactions of alcohols, which result in hydroxyl substitution. − This work encompasses the first catalytic enantioselective C−C couplings of methanol , (>30M tons/year) and ethanol (>80M tons/year). Specifically, using iridium catalysts, methanol was coupled to dienes and allenes to form primary neopentyl alcohols, and ethanol was coupled to allylic acetates to form branched secondary homoallylic alcohols.…”

Conversion of Primary Alcohols and Butadiene to Branched Ketones via Merged Transfer Hydrogenative Carbonyl Addition–Redox Isomerization Catalyzed by Rhodium

“…Despite the promise of this approach, catalytic reactions of this type often require reductants that are not ideal (Mn, Zn, Et 3 B, Et 2 Zn, and HSiR 3 ) . Consequently, work from our laboratory has focused on the use of feedstock reductants (H 2 , 2-PrOH, and HCO 2 H) in metal-catalyzed carbonyl reductive coupling. , Additionally, we have developed a unique class of hydrogen autotransfer processes in which alcohols serve dually as reductants and carbonyl pro-electrophiles, thus enabling direct conversion of lower alcohols to higher alcohols. , Given the commercial significance of ketones across diverse chemical industries, and the fact that classical methods for their convergent construction rely on premetalated reagents, , efforts were made to exploit hydrogen transfer in metal-catalyzed ketone syntheses beyond premetalated reagents or metallic reductants (Figure ). Preexisting methods of this type include hydroacylation (which typically requires β-chelating groups to suppress decarbonylation), , “oxa-Heck” reactions (which are restricted to aryl transfer), − two reports of the reductive coupling of styrenes with anhydrides, , and, finally, recently reported formate-mediated reductive coupling–redox isomerizations of aldehydes and vinyl halides or triflates .…”

“…Preexisting methods of this type include hydroacylation (which typically requires β-chelating groups to suppress decarbonylation), , “oxa-Heck” reactions (which are restricted to aryl transfer), − two reports of the reductive coupling of styrenes with anhydrides, , and, finally, recently reported formate-mediated reductive coupling–redox isomerizations of aldehydes and vinyl halides or triflates . Here, we report a method for the direct redox–neutral conversion of primary benzylic or aliphatic alcohols and butadiene (12 × 10 6 tons/year) to branched ketones via merged transfer hydrogenative carbonyl addition–redox isomerization. − These processes represent the first examples of rhodium-catalyzed carbonyl addition via hydrogen autotransfer. , …”

Recyclable Zr/Hf-Containing Acid-Base Bifunctional Catalysts for Hydrogen Transfer Upgrading of Biofuranics: A Review

“…Therefore, the C O bond is hydrogenated while retaining the C C bond (Wu et al, 2018b;Li et al, 2018d;Jin et al, 2019;Liu et al, 2021d). Heterogeneous catalysts were wildly used in MPV reduction reactions, which can be easily recycled and also can effectively reduce industrial production costs (Santana and Krische, 2021;Pan et al, 2022). It goes without saying that the choice of materials is of great importance for the relevant catalytic system.…”