Copper(II)-Bis(oxazolme)-Cataryzed Asymmetric 1,3-Dipolar Cycloadditions of Nitrones with 2-Alkenoyl Pyridine N-Oxides

摘要

The 1,3-dipolar cycloaddition reaction of nitrones with electron-deficient alkenes is an efficient tool for the synthesis of isoxazolidines which are important intermediates for the preparation of a wide variety of natural and unnatural products, particularly alkaloids, amino acids and amino sugars. The generation of up to three stereogenic centers in a stereocontrolled way has stimulated the development of a number of catalytic enantioselective procedures for this transformation, many of them based on the use of chiral Lewis acids. However, despite some development, the reaction remains limited to a short range of substrates. On the other hand, metal complexes with bis(oxazoline) ligands (BOX) have found successful application in a large number of enantioselective reactions involving bidentate substrates.