Solvent chlorine abstraction from

The use of benzene as a solvent eliminates the chlorinated organic products in Table II. This point and the products in the table are consistent with radical abstraction (hydrogen atom transfer) from the substrate, cyclohexene, by the high valent (and likely oxometal) intermediate form of the TMSP complexes, followed by chlorine abstraction from the solvent by intermediate organic radicals. Separation and analysis of the two phases after the reaction reveals that the polyoxometalate is intact. 

Photolysis of aryl or pyridyl oxime esters in pyridine provides a-phenylpyridines as the major products together with bipyridyls (84TL3887). Rate constants for the addition of phenyl radical to protonated and non-protonated 4-substituted pyridines have been determined by studing the competition between phenyl radical addition and chlorine abstraction from carbon. The 4-arylpyridines were the major products, and no 3-substituted pyridines were observed. Among the solvents studied (MeCN, DMF, DMSO, and HMPA), MeCN gave the highest yields and selectivity (910PP438). 

In addition, it is clear that the quantum yields observed in the different chloromethane solvents do not reflect simply the ease of chlorine abstraction from the solvent trapping agent, and instead indicate solvent effects on the primary quantum yields for the formation of reactive metal radicals. 

Possible additional support for a photonucleophilic hydride transfer mechanism comes from further observations on the photolysis of PCP. When this compound was irradiated in methanol rather than in water, no oxidation or displacement of chlorine by hydroxyl was detected instead, photoreduction produced primarily 2,3,5,6-tetrachlorophenol (XVI) together with a small proportion of what seemed to be the 2,3,4,5-tetra-chloro isomer (Figure 6) (52). Hydrogen abstraction from solvent by polychlorophenyl radicals is expected to produce some of each of the three isomers representing replacement of an o-, m-, and p-chlorine, with the first two predominating because of doubled probability. 

When n = 0 or 1, the system appeared to be too rigid to allow the radical pair created upon hydrogen abstraction to form a carbon-carbon bond. Hence a considerable amount of chlorine appears in the product from radical abstraction from the solvent, carbon tetrachloride. When n = 2 the radicals are able to form a carbon-carbon bond. After a five-step workup of the crude irradiation product including reduction with LiAlH4, acetylation, dehydration, oxidation with ruthenium tetroxide, and hydrolysis a 16% yield of previously unreported 12-keto-3a-chlorestanol was obtained. However,... 

It has been known that the electrolysis in an MeCN- NaClO system generates an acid The hydrogen has to originate from the solvent. A mechanism for hydrogen abstraction from acetonitrile by the electrooxidatively generated radical 104- to produce perchloric acid has been proposed, but no evidence for the succinonitrile formation appeared (Eq. (5)). The detection of the 104- radical by the aid of HSR was tried But it was found to be difficult to differentiate between the perchlorate radical and the radical from chlorine dioxide The electrolysis in a CH Clj—... 

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