Indirect Electrochemical Oxidations Using Triarylamines as Redox Catalysts

3 Indirect Electrochemical Oxidations Using Triarylamines as Redox Catalysts 

As mentioned above, it is difficult to find organic compounds which are suitable as redox catalysts for oxidations. This is the case because organic cation radicals, which are mostly the active forms in indirect electrochemical oxidations, are usually easily attacked by nucleophiles, thus eliminating them from the regenerative cycle. Therefore, the cation radicals must be stabilized towards the reaction with nucleophiles. Nelson et al. demonstrated that the cation radicals of triaryl amines and related compounds are very stable if the para positions of the aryl 

Triarylamine cation radicals seem to be able to react in two different ways 1 — as simple one-electron transfer agents (mechanism A, Sect. 2.3) 2 — as chemical catalysts (mechanism B, Sect. 2.3) for oxidations in which the redox step is 

oxidation reactions are possible under very mild conditions and with high selectivities. Therefore, this method is especially useful for oxidative deprotections. For example, the oxidative cleavage of the carbon-sulfur bond is easily possible according to Eq. (103). In this way, disulfides and follow-up products of carbenium 

By indirect anodic cleavage of carbon-sulfur bonds it is also possible to initiate rearrangements (Eqs. (105)—(106)) (Table 11, No. 6). 

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