Silyl tellurides

The reductive chemoselective bis-silylation of quinones was afforded by thermal reaction with silyl tellurides. ... 

A radical mechanism has been proposed involving an initial electron transfer (ET) from the silyl telluride to the quinone followed by the formation of a phenoxy radical as precursor of the product. 

Bis(trimethylsilyl) selenide (mp -7°, bp 58-59°/ll torr)14 and bis(trimethyl-silyl) telluride (mp 13.5°, bp 74°/11 torr)14 are liquids of low volatility with revolting and persistent odors resembling garlic and rotten cabbage. They exhibit first-order H nmr spectra 2,3 [(CH3)3Si]2Se 5(CH3) 0.43 ppm,/(H—13C)... 

Some radical reactions using silyltellurides have been reported. The reaction of McsSiTePh with quinones gives the corresponding Z)w-silylated hydroquin-ones (Scheme Three-component coupling among the silyl tellurides,... 

Methyllithium (4.0 mmol, 1.0 M in diethyl ether, 4.0 mL) was added to a suspension of CuCN (2.0 mmol, 0.18 g) in THF (10 mL) at -75°C. The reaction mixture was then stirred until a clear solution was obtained and allowed to warm to room temperature. The appropriate (Z)-vinylic telluride A (2.0 mmol) or B (1.0 mmol) was added and stirred for 45 min. The solution was cooled back to -75°C and the corresponding enone (2.2 mmol) was added. After 20 min, chlorotrimethylsilane (2.6 mmol, 0.60 g) diluted in THF (5 mL) was added. The reaction mixture was stirred for 1 h, allowed to warm to room temperature and then treated with 1 1 solution of saturated aqueous NH4CI and NH4OH (20 mL), extracted with ethyl acetate (3x20 mL), dried, evaporated and the residue was purified by Kiigelrohr distillation affording the silyl enol ethers. 

In a rather more unusual process, presumably involving tellurium-lithium exchange, acyl tellurides may be converted into silyl enol ethers of acyl silanes by treatment with butyl lithium and trimethylchlorosilane. In this procedure it is the Z isomer which is the predominant product (Scheme 24)100. 

Kauffmann reported the first tellurium-lithium exchange reaction of a vinylic telluride with an organolithium compound.255 Phenyl vinyl telluride 168 was deprotonated by lithium dicyclohexylamide (LDCA) in THF, and the resulting vinyl anion 169 was reacted with chlorotrimethylsilane to give telluride 170. Vinylsilane telluroacetal 170 was then reacted with phenyllithium to give the corresponding vinyllithium, which was captured with chlorotrimethylsilane to give the bis-silylated ethane 171 (Scheme 96).255... 

Treatment of oestrone with tetraphenylbismuth monotrifluoroacetate gave oestrone phenyl ether and exemplified, in part, a new procedure for aryl ether formation.31 A detailed study was reported of the formation of benzyl ethers by sequential reaction of alcohols with chloro(phenylmethylene)dimethylammonium chloride and sodium hydrogen telluride.32 Steroidal alcohols, inter alia, were converted into hydrolytically stable silyl ethers by reaction with B N Sil or BulPh2I which were generated in situ from the selenosilane and iodine.33 The 5a-hydroxycholestane (21) was protected in this way. 

Thermally stable tris(trimethylsilyl)silyl hydrogen telluride, (Me>,Si)>,SiTeH, is isolated according to Scheme 15.17. On heahng at 130°C for 1 day in hydrocarbon soluhon (Me jSi) jSi l( l I is stable without decomposihon it readily decomposes on irradiahon with sunlight, however, forming tellurium mirror [53]. 

Me3Si)2M (M = Se, Te) can be readily made by silylation of the lithium chalcogenide. The telluride can be converted to the selenide using first Agl then Ag2Se, providing an extension to the Conversion Series established by Eaborn for silver salts (equation 68)21a,65,6 . 

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