Amines transition metal peroxide oxidation

Selective oxidation of aromatic amines to nitroso-derivatives with hydrogen peroxide and a catalyst is also studied [68, 69], In kinetic systems with transition metal complexes substrate oxidation is accompanied by H202 dissociation to H20 and 02. Therefore, in this case, the occurrence of chemical induction would be expected. 

In oxidation reactions, however, osmium is significantly more selective than catalysts derived from other transition metals. Osmium-based catalysts for the hydroxylation and amination of aUcenes are very widely used in organic synthesis. With alkaloid-derived ligands, the hydroxylation and amination reactions are highly enantioselective (see Enantioselectivity). The use of bleach, hydrogen peroxide, ferric cyanide, and oxygen have been reported as secondary oxidants for some of these reactions. 

High-valent transition metal complexes, e.g. complexes of Mo, V and Ti, catalyze numerous oxidations of organic substrates by alkyl hydroperoxides, such as epoxidation of alkenes, oxidation of tertiary amines to the corresponding N-oxides, of sulfides to sulfoxides. It is now generally understood that the active intermediates in these transformations consist of metal-alkyl peroxide complexes M—OOR in their triangular form (7a) resulting... 

The mechanism of formation of radicals from saccharin/amine complexes by higher oxidation state metals is unclear, but perhaps is related to oxidation of tertiary amines by benzoyl peroxide. Scheme 2 describes a catalytic effect of the transition metal on free radical production when both saccharine/amine and hydroperoxide initiators are present, instead of an essentially stoichiometric mechanism if only one initiator were present. 

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