Hydrosilanes-Tetrabutylammonium

Diastereoselective reduction of ketones. Trialky Isilanes can reduce aldehydes and ketones in the presence of a catalytic amount of tetrabutylammonium fluoride in HMPT cf. reductions with activated hydrosilanes, II, 554). Under these conditions esters and nitriles are not reduced. The reaction is stereoselective. Thus 2-methylcyclohcxanone is reduced selectively to cA-2-methylcyclohexanol the cvT-selectivity depends on the bulkiness of the hydrosilanc, being highest (95%) with triphenylsilane. 

Comparing the cyclic voltammograms of hydroorgano- and diorganodichlorosilanes in 0 1 M solution of tetrabutylammonium perchlorate (TBAP) in dimethoxyethane (DME), we found the former to show reduction at much lower potentials. Therefore, cathodic precipitation of magnesium occurs to a larger extent, thus leading to lower yields of poly(hydrosilanes). 

Heating a tertiary alcohol with l-(trimethylsilyl)iniidazole (abbreviated TMSIM. by-product imidazole) at 100 °C accomplishes O-trimethylsilylation even in the presence of a trisubstituled oxirane [Scheme 4.10].Tetrabutylammonium fluoride (TBAP) catalyses the 0-silylation of alcohols with various silazanes, including l-(trimethylsilyI)imidazole, so that silylation takes place at room temperature in DMF [Scheme 4.11]. In the absence of TBAF, no silylation occurs. The use of more hindered silazanes such as the bissilyl derivative of 5,5-dimethyIhy-dantoin allows regioselective TMS or TBS protection of primary hydroxyl groups in the presence of secondary and tertiary ones. Hydrosilanes and disilanes can be used instead of silazanes in TBAF-caialysed protection of primary and secondary alcohols. ... 

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