Trichlorosilane-Tributylamine

Direction b of Scheme 1.10. The mixture of trichlorosilane and tributylamine in benzene reduces organic derivatives of two-valence sulfur such as benzene sulfenates. However, nitrobenzene sulf-enates remain intact in this system (Todres and Avagyan 1978 Scheme 1.13). 

Introduction of nitrobenzene sulfenates into the same mixture of trichlorosilane and tributylamine results in the evolution of hydrogen. As proven by Todres and Avagyan (1978), trichlorosilane with tributylamine yields the trichlorosilyl anion and tributylammonium cation. This stage starts the process involving one-electron transfer from the anion to a nitrobenzene sulfenate. At that time, nitrobenzene sulfenate produces the stable anion-radical with the tributylammonium counterion. The anion-radical gives off an unpaired electron to the proton from the counterion (see Scheme 1.14). 

In the case of DIPAMP the copper-coupling step, run with lithium diisopropyl amide and CuCl2, did not affect the stereochemistry. However, only the base-promoted reaction with trichlorosilane to give a double inversion was applicable. In this case, an empirical study showed that use of tributylamine minimized formation of the meso product. 

Addition of trichlorosilane or dichloro(methyl)silane to olefins can also be effected in the presence of tertiary amines such as pyridine, N,N,N, N -tetra-methylethylenediamine, and tributylamine or in the presence of tertiary phosphines such as triphenylphosphine.365 Amides such as dimethylformamide, V,W-diethylbenzamide, and V,7V-dibutylacetamide exert a similar catalytic effect.366 The mechanism of these base-catalyzed hydrosilations is probably also ionic. 

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