Enamide Derivatives: Versatile Building Blocks for Highly Functionalized α,β-Substituted Amines

Abstract

As demonstrated by earlier successes with enamines, nitrogen-activated C=C double bonds have considerable potential for use in the construction of various nitrogen-containing products. To expand the applications of this class of substrates, we focused on studying the reactivity of enamides and enecarbamates as promising representatives. Starting from the well-known Povarov reaction, we gradually developed other cycloaddition reactions and, more generally, an extended range of methods for α,β-difunctionalization. Our most recent work, which involves radical processes, has contributed to a significant increase in the diversity of scaffolds accessible from these nitrogenous substrates and is potentially applicable to various natural and bioactive synthetic targets. 1 Introduction 2 General Design 3 Asymmetric Brønsted Acid-Catalyzed α,β-Difunctionalization of Enamides 3.1 Intramolecular α,β-Difunctionalization of Enamides Through Cycloaddition Reactions 3.1.1 Povarov Reactions 3.1.2 Diels–Alder Reactions of 1-Azadienes 3.2 Intermolecular α,β-Difunctionalization of Enamides 3.2.1 Mannich Reactions 3.2.2 Addition to Azo Compounds 3.2.3 Halogenation Reactions 4 Radical Tandem Difunctionalization: β-Alkylation Followed by α-Functionalization of Enamides 4.1 Photoredox-Mediated Tandem α,β-Difunctionalization of Enamides 4.1.1 Oxyalkylation 4.1.2 Oxy-, Amino- and Carbotrifluoromethylation 4.2 Single-Electron Transfer-Mediated Tandem α,β-Difunctionalization of Enamides 5 Conclusion