Hydrogen abstraction by thiyl

Schmittel M, Ghorai MK (2001) Reactivity patterns of radical ions - a unifying picture of radical-anion and radical-cation transformations. In Balzani V (ed) Electron transfer in chemistry, vol 2. Organic molecules. Wiley-VCH, Weinheim, pp 5-54 Schoneich C, Bonifacic M, Dillinger U, Asmus K-D (1990) Hydrogen abstraction by thiyl radicals from activated C-H-bond of alcohols, ethers and polyunsaturated fatty acids. In Chatgilialoglu C, Asmus K-D (eds) Sulfur-centered reactive intermediates in chemistry and biology. Plenum, New York, pp 367-376... 

Schoneich C, Bonifacic M, Dillinger U, Asmus K-D (1990) Hydrogen abstraction by thiyl radicals from activated C-H-bond of alcohols, ethers and polyunsaturated fatty acids. In Chatgilialoglu C,... 

An instructive example for hydrogen abstraction by thiyl radicals, in this case from an ether, has been reported by Akhlaq et al. Experimental evidence is a racemisation of 2,5-dimethyl-tetrahydrofurane according to a reaction sequence which involves an intermediate planar radical site at the carbon a to the ether s oxygen. 

Hydrogen atom abstraction by thiyl radicals has also been shown to occur with various aliphatic and aromatic compounds [57]. Extensive studies have been conducted with respect to the thiyl reaction with alcohols and ethers in which the C-H bond of interest is activated by a-positioned hydroxyl or alkoxy groups. In these systems, an equilibrium is established, as formulated in equation (36) [9, 55] ... 

However, this is likely not to be the only process. A photolytic decomposition of di(r-butyl)disulfide in low temperature glasses is quite efficient and produces substantial amounts of 2-methyl-2-propanethiol as product which cannot be explained assuming the reaction shown above 187]. The only way to explain the production of this product is to admit the possibility of hydrogen abstraction by the r-butylthiyl radical from the matrix which is considered next. The other option is to admit the existence of hot thiyl radicals generated by photolysis. 

It has been found that 365 nm irradiation of 3-methylpentane glasses containing trapped thiyl radicals results in production of matrix radicals [27]. Because neither parent thiols nor hydrocarbons absorb in this spectral region, the production of alkyl radicals was assigned to hydrogen abstraction by photoexcited thiyl radicals from the matrix ... 

In an analogous process, the reactions of unsubstituted and 2-substituted allyl phenyl sulfides with (TMSlsSiH give a facile entry to allyl fns(trimethylsilyl) silanes in high yields (Reaction 26). In this case, the addition of (TMSlsSi radical to the double bond is followed by the S-scission with ejection of a thiyl radical, thus affording the transposed double bond. Hydrogen abstraction from (TMSlsSiH by PhS radical completes the cycle of these chain reactions. ... 

Thiyl radicals, RS-, may be obtained by hydrogen abstraction from RSH, and will then add readily to alkenes by a chain reaction analogous... 

RSOO are generated by the hydrogen abstraction from thiols by OH radicals, alcohol radicals, etc., producing thiyl radicals (RS ) which on reaction with oxygen produce RSOO [Eqs. (34) and (35)]. Alternatively, reaction of alkylsulfonyl chloride with e q produces alkyl sulfonyl peroxyl radicals [Eq. (36)]. 

The reactions of bicyclobutane with radicals have been the subject of a relatively limited number of investigations. Two types of reactions have been observed (1) addition to the central bond and (2) hydrogen abstraction. Which of the two reactions will occur is determined by the nature of the attacking radical. Thus, reagents such as thiyl radicals add across the central bond. On the other hand, t-butoxyl, which is generally the radical of preference for hydrogen abstraction, reacts with bicyclobutane to give the 2-bicyclobutyl radical. 

Hydrogen abstraction results in positive ion formation as shortlived species that may in turn act as oxidants [99] or may rearrange from thiols [98]. In addition, formation of a thiyl radical has been detected using pulse radiolysis [99]. These intermediates are not stable and decay rapidly via several pathways [96] that may result in the formation of oxy acids (cysteic acid or disulphides). However, the proportion of the product yielded is governed by many factors, including oxygen tension and substrate concentration. 

---