Some Recent Advances in Metallosalen Chemistry

Metal-oxenoid, -nitrenoid, and -carbenoid are potent active species and react with C=C and C-H bonds, forming C-O, C-N and C-C bonds, respectively. When the metal ion carries an appropriate chiral ligand, these bond-forming reactions occur in an enantioselective manner. In the last decade, many well-designed salen ligands have been found to serve as efficient chiral auxiliaries for these reactions. In this article are described highly enantioselective oxene, nitrene, and carbene transfer reactions using chiral first- and second-generation metallosalen complexes as catalysts. In addition to these reactions, asymmetric oxidation using metallosalen complexes as the catalyst and molecular oxygen or hydrogen peroxide as the terminal oxidant is also described.