Aryl radical-cation

Cell wall peroxidase/H202 — Formation of phenoxy radicals of monolignols 1. Lignin peroxidase/H202 — Formation of aryl radical cations of nonphenolic units... 

Apparently, surface adsorption of the radical ion intermediates so stabilizes and directs their chemical reactivity that combination with superoxide rather than deprotonation of the aryl radical cation are observed. 

Aryl radical cations generated by electron-transfer processes from methoxy substituted arenes to DCN, tethered by oxygen, nitrogen as well as carbon nucleophile leads to intramolecular cyclizations (Scheme 8.67). The synthetic potentials of... 

Generation of substituted aryl radical cations in the presence of nucleophiles can lead to products of side-chain substitution (processes such as anodic benzylic substitution of toluenes, which are dealt with in a separate chapter) or to products of addition to the aromatic ring itself. Nuclear addition products in /j /m-substituted systems have been proposed to form in essentially one of two ways, depending on substitution pattern and reaction conditions. Radical cations formed by electrochemical reaction (E) may be trapped by chemical reaction (C) with a nucleophile (or its anion). Repeating this sequence leads to nuclear addition products (LXV), formed by what is referred to as the ECEC mechanism [Eq. (31)] [74]. An analogous pattern may be inferred for or / (9-substituted systems. 

Cu(L)(Tpph)]BF4 (L = l-lpyrid-l-yb-S-ll -dimethoxyphenyl)-pyrazole) has been electrochemically investigated. It has been concluded that the intramolecular tt-tt interaction existing in the complex (Fig. 3.21) has no effect on the lifetime of an aryl radical cation.123... 

Dicyanobenzene was converted into 3-cyanobenzoic acid by using the bacterium Rhodococcus rhodochrocus ". Intramolecular electron transfer involving isomeric forms of dicyanobenzene was investigated in detaiP and the mechanisms of electroreduction of all three isomers were studied. When dicyanobenzene was used as catalyst in photoamination reactions of arenes, the first step of the reaction was the formation of an aryl radical cation by electron transfer from the aromatic hydrocarbon to m-dicyano-benzene. ... 

Nitronium salts are capable to induce the OCA reaction via generation of aryl radical-cations, even with relatively electron-poor arenes, such as benzene [105]. Namely, NOBF4 in catalytic amount (1-5 mol%) efficiently catalysed the oxidative coupling reactions of polyalkoxybenzenes in dichloromethane (containing 20% trifluoroacetic acid) under exposure to air affording the corresponding biaryls in almost quantitative yields [105]. Finally, oxidative couplings of arenes can be accomplished under the classical Scholl reaction conditions [106]. For example, 1-ethoxynaphthalene (419) was coupled to binaphthyl 420 by reaction with anhydrous aluminum chloride and nitrobenzene (as oxidant) in 65% yield, Scheme 28. 

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