Enamines, with one amino group connected with carbon-carbon double bond, are key frameworks of many drugs. They have important applications in organic synthesis, especially in the synthesis of natural products and N-containing heterocycles owing to their unique structures. Therefore, the synthesis of enamines is particularly noticeable. In order to develop novel and applicable methodologies to synthesize enamines, the recent progress in their synthesis has been reviewed herein. Firstly, the related work of conventional synthesis, which include condensation reaction, addition reaction, heterocyclic cracking Curtius rearrangement, Wittig reaction, α, β-elimination of amide, reductive acylation of ketoxime, etc. has been summarized. Then, the catalytic amination of olefins to prepare enamine has been introduced in detail. In transition-metal catalyzed (mainly Cu (Ⅰ or Ⅱ) or Pd (0 or Ⅱ)) Buchwald-Hartwig reaction, the research progress of using various substituted olefins as substrates, including halogenated olefins, pseudohalogenated olefins and alkenyl boronic acid, has been reviewed. The methodology called Aza-Wacker oxidative coupling reaction to synthesize enamine via C (sp²)-H direct activation to construct C-N bond with different amines have also been summarized. Finally, the progress to prepare enamines and their derivatives by hydroamination of alkynes has been introduced here. It is of great significance for the development of the new methodologies to synthesize enamine.
Contents
1 Introduction
2 Synthese of enamine by traditional methods
3 Synthese of enamine from olefins and amines
3.1 Synthese of enamine from substituted olefins and amines
3.2 Synthese of enamine by C-H activation of olefins
4 Synthese of enamine from alkynes and amines
4.1 Synthese of enamine from alkynes and aliphatic amines and its derivatives
4.2 Synthese of enamine from alkynes and aromatic amines
4.3 Synthese of enamine from alkynes and amides and its derivatives
4.4 Synthese of enamine from alkynes and diazo or azide
5 Conclusion