Electron-transfer Reactions of Amines

Radical Cations of n-Donors — Electron Transfer Reactions of Amines 169... 

In summary, the electron transfer reactions of amines offer an interesting variety of pathways, involving free radical or ionic intermediates and leading to two-electron oxidation as well as coupling and fragmentation reactions. In many systems, however, the most important reaction involves electron return from the acceptor radical anion, i.e. quenching of an excited state without net chemical change. 

In this chapter, we focus on the mechanistic and synthetic aspects of electron-transfer reactions of amines. The role of electron transfer of amines in enzyme-catalyzed oxidations of amines is also briefly discussed. 

The mechanism of electron-transfer reactions of amines has been studied by different methods, including the thermochemical, electrochemical, photochemical, and radiation chemical techniques. 

Picosecond and nanosecond transient spectroscopic studies to elucidate the nature of various intermediates formed in the photoinduced electron-transfer reaction of amines have been most extensive for the ketone-amine systems. These studies have been described in detail in a recent review by Yoon et al. [10]. Some aspects of these studies are briefly described here. In the earlier studies of Cohen and coworkers, the photochemical reactions of benzophenone with aliphatic amines were probed by fluorescence quenching, determination of product quantum yields, and nanosecond laser-flash photolysis [143-147]. They proposed that the reactions of amines with... 

Electron-transfer Reactions of Amines in Biochemical Systems... 

Electron-transfer reactions of amines are of significant importance in biochemical systems. Enzymes known to catalyze the oxidative dealkylation of amines include monoamine oxidase [16, 17], cytochrome-P450 [18, 184-186], horseradish peroxidase [187], hemoproteins [188, 189], and chloroperoxidase [187, 188]. N-dealkylation of amines by peroxidases are generally accepted to occur via one-electron transfer, whereas the role of electron transfer in reactions catalyzed by enzymes such as monoamine oxidase [16, 17] and cytochrome P-450 [18, 184, 185] is currently a topic of debate. 

The a-aminoalkyl radicals as well as iminium ions generated as intermediates in electron-transfer reactions of amines can be used for bringing about synthetically useful transformations of amines. The synthetic applications of amine oxidation reactions brought about by thermal, electrochemical and photochemical methods as discussed below. 

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