Reductive Removal of Chalcogen Groups RS and RSe

The removal of the tritylthio (Ph3CS) protecting group used in guanine derivatives has been accomplished in a good yield by the action of (TMS)3SiH under free-radical conditions (Reaction 4.22) [49]. 

Secondary alkyl selenides are reduced by (TMS)3SiH, as expected in view of the affinity of silyl radicals for selenium-containing substrates (Table 4.3) [40]. Reaction (4.23) shows the phenylseleno group removal from the 2 position of nucleoside [50]. Similarly to 1,3-dithiolanes and 1,3-dithianes, five- and six-membered cyclic selenoacetals can be monoreduced to the corresponding selenides in the presence of (TMS)3SiH [51]. The silicon hydride preferentially approached from the less hindered equatorial position to give transicis ratios of 30/70 and 25/75 for the five-membered (Reaction 4.24) and six-membered cyclic selenoacetals, respectively. 

Phenyl selenoesters have been reported to undergo reduction to the corresponding aldehydes and/or alkanes in the presence of (TMS)3SiH under free- 

The removal of the hydroxy group has been achieved from an appropriate selenocarbonate by heating in the presence of (TMS)3SiH and AIBN in benzene [55]. Reaction (4.27) was inserted in the multistep synthesis of an alkaloid. The deoxygenation was achieved with 87% efficiency of the two steps. 

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