Alkylsilanes coupling reactions

Alkylsilanes activated in situ by TBAF are also applicable to the cross-coupling reaction with aryl halides (Scheme The fact that the reaction requires excess... 

The cross-coupling reaction of an optically active alkylsilane gives us valuable information on the stereochemistry in transmetallation. The reaction of (5)-l-phenyl-1-(trifluorosilyl)ethane (34% ee) with 4-acetylphenyl triflate in the presence of 5 mol % of Pd(PPh3>4 and TBAF (2 equiv) at 50 °C gave (5)-1-phenyl-l-(4-acetylphenyl)ethane of 33% ee with nearly complete retention of configuration. At higher temperatures, ee of the product decreased linearly, and above 75 °C inversion of configuration predominated (Scheme 26). Similar temperature dependency was observed also in the reaction of 3-formylphenyl triflate. 

Of-Silylalkanenitriles couples with aryl halides to give a variety of cx-arylalkanenitriles (Scheme 3-169). On the other hand, alkyl cross-coupling reaction using alkylsilane reagents as nucleophiles is successful only with... 

The reactivity described above for borates in the presence of DCN has also been observed for tetra-alkylsilanes, tetra-alkylgermanes and tetra-alkylstannanes in the presence of dicyano-benzene and tetracyanobenzene, and in the presence of pyrilium salts.Thus ultra-violet irradiation of 1,4-dicyanobenzene in acetonitrile with one of tetrabutylsilane, tetrabutylstannane or tetrabutylgermane yielded 4-butylcyanobenzene, and excitation of 2,4,6-triphenylpyrilium tetrafluoroborate under the same conditions yielded the addition products (147) and (148)Both reactions are thought to proceed by electron transfer from the tetra-alkyl metal to the excited state of the salt the radical cation produced then dissociates to the trialkyl metal cation and an alkyl radical which couples with the cyanoarene or the pyrilium ring. 

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