Copper-induced reaction

Another copper-induced reaction which may be reinterpreted in view of our mechanism is the copper-induced chlorination of ketones (64). It seems reasonable to suggest that Cu(II) bound to the ketone is oxidized to Cu(III) by C11CI2, which, in the given medium, is less stable than Cu(I). Subsequently, Cu(III) oxidizes its chlorine ligand in a double electron transfer to C1+, followed by the latter s addition to the enolic double bond. 

The specific phenomenon in this copper-induced reaction is the configuration of the reduced complex which facilitates the oxidation of Cu(I) to Cu(III). The effect of configuration on the redox behavior of a ligand may be important in interpreting metal-induced enzymatic redox reactions. 

Indirect evidence such as this does no more than indicate that the intermediate formed in copper-induced reactions is different from the carbenes thought to be produced in thermal and photochemical decompositions of diazoalkanes. However, the long-held view (Yates, 1952) that a carbene-copper complex is the reactive intermediate in these catalysed reactions gains strong support from a recent observation that the decomposition of ethyl diazoacetate induced by the chiral complex... 

Wurtz-Ullmann processes can be carried out with copper or zinc, prepared by the sonochemical Rieke method. Lindley et al examined the fundamental aspects of the copper-induced reaction of 2-nitro iodobenzene (Eq. 44). 9 Almost quantitative yields are obtained with only a fourfold excess of copper flakes at 60 C in DMF under probe sonication, with a rate multiplied by a factor of ca. 50. 

It was found that the value of F, is markedly increased by ions which are effective catalysts of oxidation reactions of peroxydisulphate. These are silver(I) copper(n), and iron(III). Cobalt(II) and nickel(II) ions, although they are good catalysts for the decomposition of hydrogen peroxide, exert their effect merely as inert electrolytes in the induced reaction. Therefore it can be concluded that, in this process, activation of the rather less reactive 8203 is more important than that of hydrogen peroxide . ... 

For the copper-induced decomposition of diazodiphenylmethane in acetonitrile, a fundamental difference in the catalytic action of Cu C104 and Cu ClO was detected. Whilst with CuC104, intermediary copper carbenoids are believed to be responsible for the mainly formed benzophenone azine402, CufClO initiates a chain reaction, promoted by radical cations and yielding mainly tetraphenylethene... 

Lavelli V, Peri C and Rizzolo A. 2000. Antioxidant activity of tomato products as studied by model reactions using xanthine oxidase, myeloperoxidase, and copper-induced lipid peroxidation. J Agric Food Chem 48(5) 1442—1448. 

The mechanism of these reactions has been extensively studied. A recent book summarizes this literamre . A review refers to many other examples involving conjugate addition of organomagnesium reagents to a,/3-unsaturated ketones. It includes the stereochemistry of the reaction and copper-induced conjugate additions. ... 

P. Wenger and C. Urfer. N. Smith found that in the oxidation of tin or copper in air, ammonia is simultaneously oxidized—induced reactions zinc has no action, but in glass dishes positive results were sometimes obtained—while only a slight action -was observed in the oxidation of ferrous and manganous hydroxides. 

This reaction generates reactive hydroxyl radicals that can damage biomolecules. However, cellular hydrogen peroxide is rapidly removed by catalase and concentrations are very low, usually in the submicromolar concentration range. A Fenton-type reaction may therefore not be the primary cause of copper toxicity (Kaim and Rail, 1996). An alternative route of copper-induced cell damage is the depletion of sulfhydryls by redox cychng as described in reactions (2) and (3) ... 

Reaction (3) will in fact generate hydrogen peroxide, which could fuel a Fenton-type reaction and thus enhance copper-induced damage by reactions (2) and (3). 

High concentrations of heavy metals that affect, directly or indirectly, the redox potential in the reducing intracellular milieu, particularly copper, induce the formation of reactive oxygen species. These, in turn, can trigger the chain reaction causing lipid peroxidation, which affects membrane integrity and induces structural changes to proteins and nucleic acids that can result in cell death. 

Farina et al. have shown that copper(I) can accelerate Stille coupling reactions [208], but examples of copper-induced cross-coupling in the absence of palladium catalysts have also been described recently. 

Cohen, T., Poeth, T. Copper-Induced coupling of vinyl halides. Stereochemistry of the Ullmann reaction. J. Am. Chem. Soc. 1972, 94, 4363 364. 

Ullman reaction. Synthesis of biaryls by copper-induced coupling of aryl halides. Similar coupling of aryl halides with aroxides yields diaryl ethers. (A modification of the Fittig synthesis in which copper powder is used instead of sodium.)... 

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