Oxidation of carbanions

The resultant radical (86) can, in turn, be reduced back to the carbanion by shaking with sodium amalgam. In suitable cases, e.g. (87), the oxidation of carbanions with one-electron oxidising agents, usually iodine, can be useful synthetically for forming a carbon-carbon bond, through dimerisation (— 88) of the resultant radical (89) ... 

One electron oxidation of monocarbanions leads to carbon radicals and two electron oxidation gives carbocations. In most of these oxidations, the mechanism is not known, though progress is being made on some mechanisms. But there appears to be a parallelism between base strength and ease of oxidation of carbanions. 

Flavin oxidation of carbanions has also been of much concern since active intermediates in some flavoenzyme-mediated reactions (amino acid oxidase, lactate oxidase, etc.) are carbanions (Kosman, 1977). Flavin oxidation of nitroethane carbanion (20), which had not been achieved in non-enzymatic systems, occurs with [56] bound to CTAB micelles (Shinkai etal., 1976b). This suggests that the nitroethane carbanion is also activated by the micellar environment. 

Radicals are generated at the anode by oxidation of carbanions (Scheme lb), for example, alkoxides and carboxylates (see Chapter 5, 6), and at the cathode by reduction of protonated carbonyl compounds or onium salts (Scheme Ic) (see Chapter 7). Thereby, a wide choice of different radical structures can be mildly and simply... 

Received October 9, 1967. Work supported by a grant from the Petroleum Research Fund administered by the American Chemical Society. Part III in a series on Oxidation of Carbanions. Part II (21) was published in 1967. 

The second electronic transfer to the oxygen produces the diradical (C) which evolves into monomer formation. The latter possibility (IV) is a homolytlc cleavage giving another anion radical. If the process follows scheme III or IV, we must obtain monomer formation after the oxidation reaction in all cases. We have carried out the oxidation of carbanionic dimers derived from isoprene, crmethylstyrene, styrene, 1,1-diphenylethylene. 

A useful oxidizing agent. Will convert organic sulfides to sulfoxides without overoxidation and disubstituted enamines to a-aminoketones. Most useful is the oxidation of carbanions to hydroxyl groups. 

As the oxidation potential clearly shows, carbanions may easily be oxidized by the anodic method. The most typical process of the anodic oxidation of carbanions is the formation of radical species (equation 52). 

This is a useful reaction for the formation of a carbon-carbon bond via dimerization of the radicals formed by the oxidation of carbanions. 

In view of the ease of oxidation of carbanions (in the form of organometallies, say RLi or RMgX), one would predict that the reaction between a carbanion and a radical cation of even low oxidizing power would lead to very rapid initial electron transfer and hence that products would be derived from attack of R on ArH. Somewhat surprisingly, such studies have to our knowledge not been performed before but should be of considerable interest.. .. 

Oxidation of carbanions by molecular oxygen is also an important reaction. Equation (3.10) shows the oxidation of the anion of triphenylmethane by molecular oxygen in a solution composed of 80% DMF and 20% t-butyl alcohol. Addition of water to the reaction mixture allowed isolation of triphenylmethyl hydroperoxide in high yields (e.g., 87%). When the reaction was carried out in 80% DMSO-20%... 

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