With hydrogen peroxide in acetic acid

Weak to moderate chemiluminescence has been reported from a large number of other Hquid-phase oxidation reactions (1,128,136). The Hst includes reactions of carbenes with oxygen (137), phenanthrene quinone with oxygen in alkaline ethanol (138), coumarin derivatives with hydrogen peroxide in acetic acid (139), nitriles with alkaline hydrogen peroxide (140), and reactions that produce electron-accepting radicals such as HO in the presence of carbonate ions (141). In the latter, exemplified by the reaction of h on(II) with H2O2 and KHCO, the carbonate radical anion is probably a key intermediate and may account for many observations of weak chemiluminescence in oxidation reactions. 

A U.S. patent describes the reaction of commercial oleic acid with hydrogen peroxide in acetic acid foUowed by air oxidation using a heavy metal compound and an inorganic bromine or chlorine compound to catalyze the oxidation. ExceUent yields of dibasic acids are obtained (up to 99%) containing up to 72% azelaic acid (55). 

IV-Oxidation of cinnoline (2) with hydrogen peroxide in acetic acid results in the formation of four products cinnoline 1-oxide (92 26%), cinnoline 2-oxide (93 50%), cinnoline... 

Benzocyclobutene-l,2-dione (11) can be condensed with benzene-1.2-diamine to provide an annulated quinoxaline (cf. Houben-Weyl, Vol. E9b/Part 2, p203), which on oxidation with hydrogen peroxide in acetic acid leads to the 1,4-diazocine derivative 12.34... 

A number of 4//-thiopyrans were converted to their corresponding sulfones with hydrogen peroxide in acetic acid 132... 

The first synthesis of stable 3-hydroperoxy-sultams (24) which are a new class of sultam with oxidising properties, was reported. The synthesis involved oxidation of the isothiazolium salts (23) with hydrogen peroxide in acetic acid. Reduction of (24) with aqueous sodium bisulphite afforded the corresponding novel 3-hydroxysultams whereas thermolysis in ethanol resulted in the elimination of water to give 3-ketone derivatives, which are versatile as dieneophiles <96T783>. 

Oxidation on the sulfur atom of pyrrolo-benzothiazepine 175 (Scheme 34, Section 2.3.1 (1994MI283)), indolo benzothiazepine (Scheme 65, Section 3.3.1.2 (1998MI139)) and pyrrolo-benzothiadiazepine (Scheme 74, Section 4.2 (1994SC2685)) proceeds smoothly with hydrogen peroxide in acetic acid or with MCPBA to afford cyclic sulfones in good yields. 

Thiadiazole sulfides are readily oxidised to the corresponding sulfoxides and sulfones. For example, the sulfide (139) is converted into the sulfoxide (140) (Equation (19)) using m-chloroperbenzoic acid <84CHEC-I(6)463> and reaction of the 5-methylthio derivative (137) (R = Ph) with hydrogen peroxide in acetic acid gives the sulfone (141) (R = Ph) (Equation (20)) (89MI 408-0l>. 

For benzo[Z ]thiophene the heterocycle is rather more resistant to ring opening and oxidation with hydrogen peroxide in acetic acid at 95 C, for example, gives the 1,1-dioxide (Scheme 7.22) reduction with either sodium and ethanol or triethylsilane in trifluoroacetic acid affords 2,3-dihydrobenzo[Z)]thiophene. Electrophiles give mainly 3-substituted benzo[Z ]thiophenes, although these products are often accompanied by smaller amounts of the 2-isomers. 

Methyl-2,4,6-triphenyl-2f/-thiopyran (2461) reacts with hydrogen peroxide in acetic acid to produce sulfoxide 411,39 whereas condensed 2//-thio-pyrans 412 and 414 gave the corresponding sulfones 413100 and 415,368 respectively. 

With hydrogen peroxide in acetic acid 1,2,4-benzotriazine gave 1,2,4-benzotriazine 1-oxide and benzotriazole, but oxidation with MCPBA afforded a mixture of the 1-oxide and the 2-oxide (82T1793). 

Isatoic anhydride (223 R = H) is easily prepared by passing phosgene into a solution of anthranilic acid in dilute hydrochloric acid (5SOSC(3)488), and clearly this approach can be used to form derivatives substituted in the benzene ring. There is an alternative approach, namely the Baeyer-Villiger oxidation of isatins with hydrogen peroxide in acetic acid (Scheme 100) < 0AG(E)222>. 

The N-oxidation of 1,6-naphthyridine with hydrogen peroxide in acetic acid forms the 2-oxo (116) and 1-hydroxy-2-oxo derivatives (117), along... 

Phenylazirine (178), the photolysis product of a-azidostyrene (177), dimerizes on standing to 2,5-dihydro-3,6-diphenylpyrazine (179). The latter compound, unlike the isomeric 2,3-dihydro-5,6-diphenyl-pyrazine is readily aromatized by treatment with hydrogen peroxide in acetic acid.378 2,5-Dibenzyloxy-2,5-dihydropyrazine is prepared by... 

The parent 1,2-dithiolylium ion (4) is readily prepared by treatment of l,2-dithiole-3-thione (3b R = R = H) with hydrogen peroxide in acetic acid (65JCS32). The method may be applied to the alkyl and aryl derivatives with equal success. For cations with 3- and 5-substitution the acid catalyzed reactions of j8-dicarbonyl compounds with hydrogen disulfide or equivalent are best (80AHC(27)l5i), whereas the benzo-1,2-dithiolylium ion (172) and related compounds are best prepared by ring contraction of benzo-l,3-dithiins (171) (63LA(661)84>. 

The unsubstituted 1,3-dithiolylium salt (1) can be prepared by reaction of l,3-dithiole-2-thione (21) with peracetic acid in acetone or with hydrogen peroxide in acetic acid (76S489). Another method includes borohydride reduction of 2-methylthio-l,3-dithiolylium salts to the 2-methylthio-l,3-dithiole followed by acidification (76S489). 

Angeli38,112 first observed that pyrrole with hydrogen peroxide in acetic acid developed a dark color and later a black precipitate. This product, which contains oxygen, was named pyrrole black . Its physical characteristics were very similar to those of natural melanins and this fact stimulated research on the structure of this product, considered an interesting model for natural pigments. 

Methoxypyridazine when treated with hydrogen peroxide in acetic acid yielded 3-methoxypyridazine 1-oxide, obtainable also by catalytic dehalogenation of 3-methoxy-6-chloropyridazine... 

Oxidation of 4-methoxypyridazine has been carried out with hydrogen peroxide in acetic acid and a mixture of 4-methoxypyridazine 1-oxide (11%), 2-oxide (8%), and 4(l T)-pyridazinone (2%) was isolated,the last compound resulting from hydrolysis. If the reaction temperature is raised to 100°, in addition to the foregoing three compounds l-methyl-4(l//)-p3Tidazinone is formed in very low yield. Of other alkoxypyridazines to be mentioned, 6-chloro-3,4-dimethoxypyridazine when oxidized with monoperphthalic acid yielded only the 1-oxide in 50% yield. 

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