Dimerization reactions nickel peroxide

Dimerization can also be achieved using nickel peroxide " or through a photooxidation reaction. In these cases, 4-monosubstituted-5(4//)-oxazolones 293 are converted to the corresponding 4,4 -bis(oxazolones) 294 (Scheme 7.97 ... 

The one-electron oxidation of a secondary amine results in the formation of a secondary aminium ion which on deprotonation gives an aminyl radical (Scheme 1). The nature of the final products derived from these intermediates dqiends very much on the structure of the substrate and the reaction conditions. If the amine has a hydrogen atom on the a-carbon atom the major products usually result from deprotonation at this a-position. With aromatic secondary amines, products can result from coupling of the delocalized radicals at a ring carbon atom. The formal dimerization of aminyl radicals shown in Scheme 21 is therefore not often a useful method of preparation of hydrazines. Nickel peroxide has been used to oxidize diphenylamine to tetraphenylhydrazine in moderate yield, and other secondary arylamines also give... 

Oxidation of 2,4-diaryl-5(4//)-oxazolones (94) with molecular oxygen gives dimeric products (Equation (7)) <9iT568i>. The reaction rate is dependent on the solvent and oxygen concentration. The oxidation is faster in highly polar solvents, such as DMSO and DMF, that favor the mesoionic form. The dimers are also formed by nickel peroxide oxidation <85T234l>. 

Contact with many organic compounds can lead to immediate fires or violent explosions (consult Bretherick for references and examples). Hydrogen peroxide reacts with certain organic functional groups (ethers, acetals, etc.) to form peroxides, which may explode upon concentration. Reaction with acetone generates explosive cyclic dimeric and trimeric peroxides. Explosions may also occur on exposure of hydrogen peroxide to metals such as sodium, potassium, magnesium, copper, iron, and nickel. 

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