Phenyl Substituted Silicon Hydrides

Although under canonical radical chain conditions these silanes are poor reducing agents, there are some interesting applications, in particular, using Ph2SiH2 [100]. For example, the reaction of a variety of substituted adamantanes 

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Phenyl or mixed alkyl/phenyl substituted silicon hydrides show similar reactivities to trialkylsilanes. Indeed, by replacing one alkyl by a phenyl group the effect on the hydrogen donating ability of SiH moiety increases only slightly. ... 

The addition reaction of alkyl and/or phenyl substituted silicon hydrides to acetylenes has limitations mainly due to the hydrogen donation step (cf. Scheme 5.1). Reaction (5.17) shows that the replacement of Ph by MesSi group in silanes made the reaction easier, the effect being cumulative. Indeed, the reaction time decreased from 88 h for PhsSiH to 3h for (TMS)3SiH [39], together with the amelioration of yields, and a slightly better cis stereoselectivity. 

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. 

Substitution of phenyl for methyl groups on the siloxane increases the radiation resistance. Silicone hydride groups are highly sensitive to radiation... 

We invoke 7c-stacking of the alkene with a phenyl moiety on the silicon protecting group (since this high degree of selectivity was only observed for TBDPS and not with TBS), in the precursor to explain this remarkable selectivity (Figure 1). Lewis acid induced reduction of the epoxide with sodium cyanoborohydride led regioselectively to the 1,3-diol (11) the hydride attacks the more substituted position via an S 2 mechanism. ... 

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