The Electron-Way: Metal-Catalyzed Reductive Umpolung Reactions of Saturated and α,β-Unsaturated Carbonyl Derivatives

Abstract

Reductive umpolung reactions of saturated and unsaturated carbonyl compounds enable the direct synthesis of 1,2-, 1,4-, 1,6-, etc. substituted carbon frameworks that are difficult to access by other methodologies. Herein, the evolution from stoichiometric to catalytic processes with high chemo-, regio- and stereoselectivity is discussed for each carbon–carbon bond connection type. At certain points, summaries of the known reaction conditions and discussions of the underlying mechanisms are included.

1 Introduction

1.1 Redox Umpolung

2 Catalyzed Pinacol Couplings and Related Reductive Homo-Dimerization Reactions

2.1 Evolution of Catalytic Systems

2.2 Diastereoselective Pinacol Coupling Reactions

2.3 Enantioselective Pinacol Coupling Reactions

2.4 Pinacol-Type Homo-Dimerization of Imines

2.5 Reductive Homo-Dimerization of Carboxylic Acid Derivatives

3 Cross-Coupling Reactions of Aldehydes, Ketones or Imines by Catalyzed Reductive Umpolung

3.1 Cross-Pinacol Coupling of Aldehydes and Ketones

3.2 Cross-Coupling of Carbonyl Derivatives with Michael Acceptors

3.3 Cross-Coupling of Carbonyls with a Carboxylic Acid Derivative or Nitrile

4 Reductive Coupling between α,β-Unsaturated Fragments

4.1 Reductive Cyclization Reactions

4.2 Intermolecular Reductive Homo-Coupling

4.3 Intermolecular Reductive Cross-Coupling

5 Conclusion

Key words

catalysis - cross-coupling - reduction - stereoselectivity - umpolung

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