Synthetic Aspects of Metal-Catalyzed Oxidations of Amines and Related Reactions

The metabolism of amines is governed by a variety of enzymes such as amine oxidase, flavoenzyme, and cytochrome P‐450. A wide variety of compounds are produced such as ammonia and alkaloids in selective and clean oxidation reactions that proceed under mild reaction conditions. Simulation of the functions of these enzymes with simple transition metal complex catalysts may lead to the discovery of biomimetic, catalytic oxidations of amines and related compounds. Indeed, metal complex catalyzed oxidations have been found to proceed with high efficiency. The first section of this review discusses the dehydrogenative oxidations of amines with transition metal catalysts by transition metal catalysts that simulate amine oxidase. The second section highlights the catalytic oxidation of secondary amines to nitrones by simulation of flavoenzymes. The third section describes the simulation of the function of cytochrome P‐450 with lowvalent ruthenium complexes and peroxides. Biomimetic ruthenium‐catalyzed oxidations of tertiary amines, secondary amines, and other substrates such as amides, β‐lactams, nitriles, alcohols, alkenes, ketones, and even nonactivated hydrocarbons can be performed selectively under mild conditions. These three general approaches provide highly useful strategies for synthesis of fine chemicals and biologically active compounds such as alkaloids, amino acids, and β‐lactams. Simulating the reactions of enzymes is a challenge in organic synthesis. Enzymes, for example amine oxidases, flavoenzymes, and cytochrome P‐450, are a tip from nature that oxidation reactions can be conducted with catalysts. Complexes of low‐valent ruthenium are particularly suitable for synthetically useful conversions of amines, alcohols, and even hydrocarbons.