Chemistry of concerto molecular catalysis based on the metal/NH bifunctionality

Abstract

The development of conceptually new bifunctional transition-metal-based catalysts for a wide range of catalytic reactions is described. The bifunctional chiral molecular catalyst based on metalligand cooperation was originally developed for asymmetric transfer hydrogenation of ketones and imines and is now applicable to chemo- and stereoselective reductive and oxidative transformations as well as to enantioselective CC and CN bond formations with a wide scope and high practicability. The structural modification and electronic fine-tuning of the protic amine chelating ligands are crucial to develop unprecedented catalytic reactions. Cp*Ru complexes bearing a diamine (NN) or aminophosphine (PN) ligand readily activate H2, and can effect hydrogenation of polar functionalities. The bifunctional Ir complexes promote aerobic oxidative transformation of alcohols into ketones and esters and are applicable to kinetic resolution of racemic secondary alcohols. A novel imido-bridged dirhodium complex, which is a dinuclear variant of the bifunctional mononuclear amido complexes, promotes aerobic oxidation of a secondary alcohol and H2. In addition, the metal/NH bifunctional property also affects efficiently enantioselective conjugate additions. The present concerto molecular catalysts offer a great opportunity to open up new fundamentals for stereoselective molecular transformations. © 2011 The Chemical Society of Japan.