Alkanethiols phenyl-substituted

The low reactivity of alkyl and/or phenyl substituted organosilanes in reduction processes can be ameliorated in the presence of a catalytic amount of alkanethiols. The reaction mechanism is reported in Scheme 5 and shows that alkyl radicals abstract hydrogen from thiols and the resulting thiyl radical abstracts hydrogen from the silane. This procedure, which was coined polarity-reversal catalysis, has been applied to dehalogenation, deoxygenation, and desulfurization reactions.For example, 1-bromoadamantane is quantitatively reduced with 2 equiv of triethylsilane in the presence of a catalytic amount of ferf-dodecanethiol. 

The rate constants Sh and SiH were determined in cyclohexane at 60 °C relative to 2kt for the self-termination of the thiyl radicals, using the kinetic analysis of the thiol-catalysed reduction of 1-bromooctane and 1-chlorooctane by silane, respectively.24 The advantage of using a silicon hydride-thiol mixture lies in the low reactivity/solubility of alkyl- and/or phenyl-substituted orga-nosilanes in reduction processes that can be ameliorated in the presence of a catalytic amount of alkanethiol. 

Fig. 12 Schematic drawing of the orientation and packing of the biphenyl- (8) and ter-phenyl-substituted (9) alkanethiols on Au(lll) and Ag(lll) [128,130]...

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