Substituted dimethyl anilines, oxidation

The involvement of dioxaborinane as the reactive species in the borate-catalysed H2O2 oxidation of substituted dimethyl anilines, methyl-p-tolyl sulfoxide, iodide, bromide, thiosulfate, HS , and hydrazine is supported by the observed kinetics and DFT calculations. There is kinetic evidence that peroxodiborate species, formed at high ratios of boron to peroxide, is unreactive. ... 

Phenols are oxidized by NaBiO3 to polyphenylene oxides, quinones, or cyclohexa-2,4-dienone derivatives, depending on the substituents and the reaction conditions [263]. For example, 2,6-xylenol is oxidized in AcOH to afford a mixture of cyclohexa-dienone and diphenoquinone derivatives (Scheme 14.123) [264] and is oxidatively polymerized in benzene under reflux to give poly(2,6-dimethyl-l,4-phenylene) ether (Scheme 14.124) [265]. Substituted anilines and a poly(phenylene oxide) are oxidatively depolymerized by NaBiO, to afford the corresponding anils [266]. Nal iO, oxidizes olefins to vicinal hydroxy acetates or diacetates in low to moderate yield [267]. Polycyclic aromatic hydrocarbons bearing a benzylic methylene group are converted to aromatic ketones in AcOH under reflux (Scheme 14.125) [268]. 

In the presence of potassium terf-butoxide, molecular oxygen converts certain substituted primary arylamines into azo compounds through radical intermediates 4,4 -dimethoxyazobenzene is obtained in 65% yield from p-anisidine in toluene at room temperature.319 Oxidation by oxygen is more effective with a pyridine solution of the arylamine containing copper(i) chloride an 81% yield of 4,4 -bis(dimethylamino)azobenzene was obtained in this way.320 Results are particularly good with potassium te/7-butoxide in dimethyl sulfoxide,321 giving, for instance, 87% of azobenzene from aniline and also being useful for various haloanilines. 

Anodic oxidation of N, N.-dimethylaniline in methanol yields the -methoxylated derivative (72), which reacts with substituted alkenes in the presence of Lewis acid to give a wide range of tetrahydroquinolines (e.g. 73).94- The adduct (75) from N-methylaniline and allene-1,3-dicarboxylic acid dimethyl ester (7 ) can be converted into the 4-quinolone (76) on treatment with polyphosphoric acid. 95 The use of nitrobenzenes as quinoline precursors is exemplified by the reaction sequence depicted in Scheme 17. The transition-metal-catalysed transformation is thought to involve the reduction of the nitrobenzene to the corresponding aniline via a nitrene intermediate.96... 

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