Catalytic Strategies to Enantiopure Benzoins: Past and Future

Abstract

The catalytic strategies developed so far for the synthesis of enantiomerically pure benzoins are reviewed. Particular attention is given to their substrate scope and limitations. Finally, this short review highlights the advantages of more atom-economic methods that have been reported recently.1 Introduction2 Benzoin Condensation2.1 Nucleophilic Carbenes as Catalysts2.2 Homocondensation of Aromatic Aldehydes2.3 Cross-Benzoin Condensation2.4 Acyloin Condensation2.5 Biocatalytic Methods3 Organocatalytic Friedel–Crafts Reaction4 Oxidative Methods4.1 α-Hydroxylation of Ketones4.2 Ketohydroxylation of Alkenes4.3 Enantiospecific Oxidation of meso-Hydrobenzoins4.4 Kinetic Resolution of Racemic Hydrobenzoins4.5 Biocatalytic Dynamic Kinetic Resolution5 Asymmetric Hemireduction of Benzils5.1 Biocatalytic Reductions – A Brief Summary5.2 Piers Hydrosilylation of Benzils5.3 Photoreduction of Benzils to Benzoins5.4 Metal-Catalyzed Hemihydrogenation of Benzils6 Conclusion and Future Challenges