Catalytic Strategies to Enantiopure Benzoins: Past and Future

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 Introduction 2 Benzoin Condensation 2.1 Nucleophilic Carbenes as Catalysts 2.2 Homocondensation of Aromatic Aldehydes 2.3 Cross-Benzoin Condensation 2.4 Acyloin Condensation 2.5 Biocatalytic Methods 3 Organocatalytic Friedel–Crafts Reaction 4 Oxidative Methods 4.1 α-Hydroxylation of Ketones 4.2 Ketohydroxylation of Alkenes 4.3 Enantiospecific Oxidation of meso-Hydrobenzoins 4.4 Kinetic Resolution of Racemic Hydrobenzoins 4.5 Biocatalytic Dynamic Kinetic Resolution 5 Asymmetric Hemireduction of Benzils 5.1 Biocatalytic Reductions – A Brief Summary 5.2 Piers Hydrosilylation of Benzils 5.3 Photoreduction of Benzils to Benzoins 5.4 Metal-Catalyzed Hemihydrogenation of Benzils 6 Conclusion and Future Challenges