Hydrogen donors Subject

I thank Keith U. Ingold for having introduced me to this subject. When I arrived in Ottawa at the National Research Council of Canada in 1979 for three years postdoctoral work with him, very little was known on the reactivity of silyl radicals. At that time, several papers dealing with kinetics of silyl radicals were published, which allowed the reactivity of silyl radical to be translated into a quantitative base. Special thanks go to David Griller for his collaboration on the initial work on hydrogen donor abilities of silicon hydrides during the late 1980s. 

In one of the methods developed in the Kyushu Industrial Research Institute, the feed pitch is first de-ashed and distilled and then subjected to hydrogenation using hydrogen-donor solvents, such as tetrahydroquinoline, and hydrogen gas as a catalyst. The hydrogenated pitch is filtered to remove the hydrogenation catalyst and then heated, to remove the low temperature volatile matter, which is... 

Novi and coworkers124 have shown that the reaction of 2,3-bis(phenylsulfonyl)-l,4-dimethylbenzene with sodium benzenethiolate in dimethyl sulfoxide yields a mixture of substitution, cyclization and reduction products when subjected at room temperature to photostimulation by a sunlamp. These authors proposed a double chain mechanism (Scheme 17) to explain the observed products. This mechanism is supported by a set of carefully designed experiments125. The addition of PhSH, a good hydrogen atom donor, increases the percent of reduction products. When the substitution process can effectively compete with the two other processes, the increase in the relative yield of substitution (e.g., with five molar equivalents of benzenethiolate) parallels the decrease in those of both cyclization and reduction products. This suggests a common intermediate leading to the three different products. This intermediate could either be the radical anion formed by electron transfer to 2,3-bis(phenylsulfonyl)-l,4-dimethylbenzene or the a radical formed... 

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