Ketene N,S-acetals are an important class of organic synthesis intermediates, and the diversity of their functional groups determines the diversity of their reactivities. The main reactions with ketene N,S-acetals are the nucleophilic conjugate addition, the selective addition with the organometallic reagents, cyclization (forming a five-membered ring or a six-membered ring), reduction, condensation and other reactions, so it is of great significance in the research of heterocycle synthesis. This review summarizes the general methods for synthesis of ketene N,S-acetals and the research on synthesis of heterocycles from ketene N,S-acetals in the recent years, including the synthesis of N-heterocyclic compounds (pyrrole, indole, pyridine, pyrimidine), O-heterocyclic compounds (furan, pyran) and multi-component reactions. The reaction generality, reaction mechanisms or derivatization results of various types of reactions are also introduced to better understand ketene N,S-acetals molecules and to expect for the selective synthesis of object heterocyclic compounds by ketene N,S-acetals. This will promote the development and applications of ketene N,S-acetals in heterocycle synthesis. In addition, most of the heterocyclic compounds synthesized by ketene N,S-acetals have potential biological activities, and the purpose of this paper is also to promote the development of ketene N,S-acetals in the field of medicinal chemistry and pharmaceutical synthesis.
Contents
1 Introduction
2 General methods for synthesis of ketene N,S-acetals
3 Application of ketene N,S-acetals in organic synthesis
3.1 The synthesis of N-heterocycles
3.2 The synthesis of O-heterocycles
3.3 Multi-component reactions
4 Conclusion