Rearrangement, peroxide-induced

Dihydropyridazines were prepared for the first time by a peroxide-induced rearrangement of 1-phenyliminopyridines. The isomers 58 and 59 originate from peroxide attack either at C-2 or C-5 of the pyridine ring, followed by ring opening and recyclization. ... 

L. M. Jeppesen, I. Lundt, and C. Pedersen, Peroxide-induced rearrangement of carbohydrate acetals, Acta Chem. Scand, 21 (1973) 3579-3585. 

Zhao Y, Davis HW Hydrogen peroxide-induced cytoskeletal rearrangement in cultured pulmonary endothelial cells. J Cell Physiol 1998 174 370-379. 

Ideally all reactions should result from unimolecular homolysis of the relatively weak 0-0 bond. However, unimolecular rearrangement and various forms of induced and non-radical decomposition complicate the kinetics of radical generation and reduce the initiator efficiency.46 Peroxide decomposition induced by radicals and redox chemistry is covered in Sections 3.3.2.1.4 and 3.3.2.1.5 respectively. 

The reaction proceeds via a pentacoordinate hydroxycarbonium ion transition state, which cleaves to either fert-butyl alcohol or the tert-butyl cation. Since 1 mol of isobutane requires 2 mol of hydrogen peroxide to complete the reaction, one can conclude that the intermediate alcohol or carbocation reacts with excess hydrogen peroxide, giving fcrt-butyl hydroperoxide. The superacid-induced rearrangement and cleavage of the hydroperoxide results in very rapid formation of the dimethylmethyl-carboxonium ion, which, upon hydrolysis, gives acetone and methyl alcohol. 

Despite many attempts it has not been possible to oxidize 2-substituted 1,2,3-triazoles 382 to the corresponding 1-oxides 326. Peracetic acid, 3-chloroperbenzoic acid, dichloropermaleic acid, trifluoroperacetic acid, peroxydisulfuric acid, and f-pentyl hydrogen peroxide in the presence of molybdenum pentachloride all failed to oxidize 382 (1981JCS(P1)503). Alkylation of 1-hydroxytriazoles 443 invariantly produced the isomeric 3-substituted 1,2,3-triazole 1-oxides 448 (see Scheme 132). However, the 2-substituted 1,2,3-triazole 1-oxides 326 can be prepared by oxidative cyclization of 2-hydroxyiminohydrazones (1,2-hydrazonooximes, a-hydrazonooximes) 345 or by cyclization of azoxyoximes 169. Additional methods of more limited scope are reaction of nitroisoxazoles 353 with aryl-diazonium ion and base, and reaction of nitroimidazoles 355 with hydroxy-amine- or amine-induced rearrangement of nitro-substituted furoxanes 357. 

A migration of an aryl group from carbon to nitrogen takes place also in the Stieglitz rearrangement. For example, the benzylamine derivatives 234 were converted into anils 235 in a reaction induced by p-nitrobenzenesulfonyl peroxide (p-NBSP)337 (equation 94). 

Tetramethylpiperidin-l-oxyl (8) has also been used as a very fast trap for cyclopropyl-alkyl radicals, and rearranged species generated from peroxides.Peroxide decomposition is induced by 8 which then combines with the transient radicals. This work included a study of the decomposition of bis[(bicyclo[2.1.0]pentan-2-yl)carbonyl]peroxide (7) in chlorobenzene and 2,2,4-trimethylpentane good yields of trialkylhydroxylamines 9 and 10 were reported. The rate of the trapping reaction was solvent dependent and the rate constant of the extremely fast clock rearrangement of the bieyclo[2.1.0]pentan-2-yl radical was determined from the yields of the two products. 

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