Chapter 5 - Copper/chiral phosphine ligand–catalyzed enantioselective 1,3-dipole cycloaddition reactions

Abstract

Asymmetric 1,3-dipolar cycloaddition is one of the most important methods for the construction of heterocyclic compounds since it could afford numerous important heterocyclic compounds with high enantioselectivity and atom efficiency. Over the past few decades, a variety of dipoles, such as nitrile oxides, nitrones, carbonyl ylides, diazoalkanes, azomethine imines, azides, and azomethine ylides, have been successfully used in such asymmetric transformations. In particular, asymmetric 1,3-dipolar cycloaddition reactions of azomethine ylides with activated alkenes have emerged as powerful tools for the enantioselective preparation of nitrogen-containing heterocyclic compounds. In the study of the asymmetric transformation of azomethine ylides, most of the reactions require the use of Lewis bases as catalysts. Such catalysts are usually composed of transition metals Au, Ag, Pd, Ir, Cu, Zn, etc., and chiral ligands in situ. Among them, copper, as an inexpensive earth-abundant metal, is the most widely used metal to catalyze 1,3-dipolar cycloaddition reactions in synergy with chiral phosphine ligands.