Oxidative arenes

KMn04 impregnated alumina oxidizes arenes to ketones within 10-30 min under solvent-free conditions using focused microwaves [111]. /i,/i-Disubstituted enamines have been successfully oxidized into carbonyl compounds with KMn04-Al203 in domestic (255 W, 82 °C) and in focused microwave ovens (330 W, 140 °C) under sol-vent-free conditions by Hamelin et al. [112]. The yields are better in the latter case. When the same reactions are conducted in an oil bath at 140 °C, no carbonyl compound formation is observed (Scheme 6.36). 

Complex iron(III) salts are frequently used in oxidative arene coupling reactions and quinone formation and tetra-n-butylammonium hexacyanoferrate(III) has several advantages in it use over more conventional oxidative procedures. When used as the dihydrogen salt, Bu4N[H2Fe(CN)6], it oxidizes 2,6-di-z-buty 1-4-methylphenol (1) to the coupled diarylethane (2), or aryl ethers (3) and (4) (Scheme 10.4), depending on the solvent. It is noteworthy that no oxidation occurs even after two days with the tris-ammonium salt. 

In a subsequent study using diphenylnitrenium ion, several intermediates were detected. With 1,3,5-trimethoxybenzene or 1,3-dimethoxybenzene, the decay of the nitrenium ion occurred concurrently with the appearance of sigma adducts (141, Fig. 13.69). These were characterized on the basis of their absorption maxima and their behavior toward pyridine bases. On the other hand, when readily oxidized arenes, such as AW-dimethylanihne were employed, the characteristic ion radicals were detected (Fig. 13.70). ... 

Arenes can also be cleaved with peroxyacetic acid831 and permanganate.636,832 Ru04 effectively oxidizes arenes to cleavage products with the use of a cooxidant such as NaT04. Violent reaction with benzene and immediate oxidation of several other aromatics such as triphenylmethane and tetralin834 take place, but oxidation products could not be isolated. Since alkanes are resistant to Ru04,... 

Electric arcs, in metal vapor synthesis, 1, 224 Electric-field-induced second harmonic generation Group 8 metallocenes, 12, 109 for hyperpolarizability measurement, 12, 107 Electrochemical cell assembly, in cyclic voltammetry, 1, 283 Electrochemical irreversibility, in cyclic voltammetry, 1, 282 Electrochemical oxidation, arene chromium carbonyls, 5, 258 Electrochemical properties, polyferrocenylsilanes, 12, 332 Electrochemical reduction, bis-Cp Zr(III) and (IV) compounds, 4, 745 Electrochemical sensors biomolecule—ferrocene conjugates... 

The carboxylates of indium and thallium are obtained by dissolving the oxides in acid. Acetate and trifluoroacetate salts are used extensively as reagents in organic synthesis. Certain other thallium compounds have been used also. The trifluoroacetate, T1(02CCF3)3, will directly thallate aromatic compounds to give arylthal-lium species, for example, C6H5T1(02CCF3)2 (cf. aromatic mercuration, Section 15-15) and oxidize arenes to biaryls. 

Reaction of aliphatic carbodiimides with 98 % H2O2 produces peroxycarboximidic acid 712, which can be used to oxidize arenes to arene oxides. ... 

Dry ozonization is also an efficient proc ure for oxidation of aliphatic primary amines into nitro groups, with yields of about 70%. Arylamines are also oxidized to nitro aronutics, albeit witii low yields. Ozone on silica gel has also been shown to oxidize arenes in some cases. ... 

Dicarboxy- IV/lb, 1012 (oxid. Aren-Spalt.), VIII, 399 (oxid. Aren-Spalt.) E7b/2, 637 (Chinolin + 03/H202) 3,5-Dicarboxy- IV/la, 337, 722... 

Cu ions, e.g. Cu(N03)2, catalyze the epoxication of alkenes by iodosylbenzene. Oxidation of alcohols to aldehydes can be effected by O2 in the presence of Cu ions and Tempo (2,2,6,6-tetramethylpiperidinyl 1-oxide). Arene hydroxylation of the binucleating ligand (206)... 

The known examples of the synthesis of higher-order annulated systems (exemplified by types XVI-XVn in Figure 2) involve photochemical cyclization followed by oxidation arene analogs of stilbenes. 

Stuart DR, Villemure E, Fagnou K (2007) Elements of regiocontrol in palladium-catalyzed oxidative arene cross-coupling. J Am Chem Soc 129 12072-12073... 

Ruthenium-based catalysts display some utility for electrophilic amination of heteroaromatic substrates. Che and coworkers have found that [Ru(TTP)(CO)J in combination with PhI=NTs will oxidize arenes such as furan, indole, and pyrrole (Fig. 13) [68]. Reactions occur optimally under the action of ultrasound, a rather unusual addendum to the standard protocol for C-H amination. More intriguingly still, iV,A-ditosylated products are isolated in most instances, a finding that is not easily resolved mechanistically. As the substrate profile for this amination process involves only electron-rich heteroaromatics, aziridination of the arene nucleus would seem a likely step along the reaction coordinate. Interestingly, no amination product is observed when stoichiometric [Ru(TMP)(NTs)2] (TMP = tetra(2,4,-6-trimethylphenyl)porphyrin) is mixed with either furan or /V-phenylpyrrole. though a reduction of the starting Ru(VI) complex to a Ru(IV) species is noted... 

Dr. Fred Guengerich at Vanderbilt University has published mechanistic schemata for cytochrome P450 involvement in an extensive array of both common and uncommon oxidative reactions and reductive reactions. Some of those are exhibited later in this chapter in a brief consideration of reductive reactions. Mechanisms for carbon hydroxylation, heteroatom oxygenation, N-dealkylation, O-dealkylation, alcohol oxidation, arene epoxidation, phenol formation, oxidation of olefins and acetylenes, reduction of nitro compounds, reductive dehalogenation, and azo reduction, to name a few, are provided. 

Bis-(2,2-dipyridyl)-silver(II) peroxydisulfate, Ag(dipy)2S2 0g. Mol. wt. 684.44. The reagent is prepared in the same way as the corresponding pyridine complex. Oxidative acetoxylation of arenes. This Ag(II) salt oxidizes arenes in acetic acid containing sodium acetate to acetoxyarenes usually in high yield. The... 

Optically active arene oxides. Arene oxides have been the subject of recent investigation because they are primary intermediates in the metabolism of... 

Potassium permanganate impregnated on alumina oxidizes arenes and alkylarenes to ketones under microwave activation [69c]. Potassium perman-ganate-triethylamine is a convenient reagent for the oxidation of benzylic methyl, methylene and methine groups [70a], Aqueous solutions of permanganate oxidize methane at 40-100 °C to produce carbon dioxide as the sole product [70b], Oxidation of hydrocarbons containing weak C-H bonds (9,10-dihydro-... 

Intermolecular electron transfer between radiolytically-oxidized arenes and [60]fullerenes (25,51) Oxidative electron transfer from [60]fullerene to various organic radical cations was studied in CH2CI2 (DCM) as a solvent. The kinetic study makes use of the unequally sized reaction partners, e.g., a large-sized electron donor and small-sized electron acceptor couple, and benefit from the low viscosity of the DCM, both elevating the diffusion-controlled limit. 

Figure 4.6 Oxidative arene vinyiation using tert-butyi hydroperoxide according to Fujiwara.

Figure 4.8 onho-Directed oxidative arene vinylation using benzoquinone as the oxidant. 

Recently it was pointed out [6] that potassium and sodium bromate oxidize arenes in good yields in a 3 2 dioxane-water solution by using cerium ammonium nitrate (CAN) as catalyst. Toluene derivatives are oxidized to ca. 1 1 mixture of benzaldehydes and benzoic acids, while ethylbenzenes are converted to acetophenones. According to the proposed mechanistic scheme, water either influences the polarity of the reaction medium or acts as the reagent, reacting with the intermediate benzylic carbonium ion to give a hydroxy derivative, which is oxidized from either Ce or BrOa ions. 

Palladium carbon/barium oxide Arenes from lactones s. 13, 904... 

Scheme 6.7 Cu(ll)-catalyzed oxidative arene C-H azidation under aerobic conditions...

Yao B, Liu Y, Zhao L, Wang DX, Wang MX (2014) Designing a Cu(ll)-ArCu(ll)-ArCu (lll)-Cu(l) catalytic cycle Cu(ll)-catalyzed oxidative arene C-H bond azidation with air as an oxidant under ambient conditions. J Org Chem 79(22) 11139-11145... 

Asymmetric Oxidative Arene-Alkene Coupling (Fujiwara-Moritani) Reactions... 

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