Aerobic oxidative N-dealkylation of secondary amines in aqueous solution catalyzed by rhodium porphyrins

Abstract

N-dealkylation demonstrates an important biochemical oxidation reaction by cytochrome P450 and other monooxygenases. In this article, catalytic oxidative N-dealkylation of secondary amines was achieved using rhodium(III) tetra (p-sulfonato-phenyl) porphyrin (( TSPP ) Rh III ) in aqueous solution with oxygen as the sole oxidant. Addition of benzaldehyde to trap primary amine product inhibited catalyst deactivation and dramatically increased reaction turnover numbers (TONs). Substrate scope examination suggested the reaction was performed with a preference for bulkier secondary amines. Kinetic study exhibited first-order kinetics with regard of ( TSPP ) Rh III catalyst. Results from the Hammett study gave a ρ value of -1.38, suggesting formation of an iminium ion intermediate in the rate determining step.