Copper catalysis for highly selective aerobic oxidation of alcohols to aldehydes/ketones
Oxidation of alcohols to aldehydes/ketones is a transformation of fundamental importance. Usually stoichiometric amounts of oxidants are required for these types of reactions. Although aerobic oxidations have been studied, there exist challenges: complicated additives, toxic or expensive catalyst(s), a large amount of base or molecular sieves, limited substrate scope, isomerization of Z CC bonds, etc. Herein, a general and practical room temperature aerobic oxidation of different types of alcohols including allenols, alkenols, propargylic alcohols, benzylic alcohols, and aliphatic alcohols in MeCN (acetonitrile) or DCE (1,2-dichloroethane) using readily available and cheap Cu(NO3)2·3H2O and TEMPO (2,2,6,6-tetramethyl-1-piperidinyloxy) or 4-HO-TEMPO as the catalysts forming aldehydes or ketones with an excellent selectivity has been developed. Some thirty to forty mmol scale reactions have been demonstrated.