Lithium triphenylsilyl

Trimethylsilylpyridine, 142 Trimethylsilyl sodium, 52-3 (E)-7-Trimethylsilyltetradec-7-ene, 16 2-Trimethylsilyltolucne, 42 Triphenylsilyl lithium, 141... 

The pale yellow crystalline trifluoroacetyl triphenylsilane and a number of other per-fluoroalkyl acyl triphenylsilanes have been prepared by simple acylation of triphenylsilyl lithium with perfluoroalkyl anhydrides122. 

Gilman s significant observation that triphenylchlorosilane is a catalyst in Wurtz-like reactions forming cyclic silanes appears to be due to intermediate formation of triphenylsilyl lithium (see Chapter 9 Cyclic Silanes). The triphenyl compounds are particularly good catalysts because the corresponding alkali-triphenylsilyl compounds are the most stable among the alkali-organo-silicon compounds. 

In recently reported investigations by Kumada et al.361 366) a mechanism is postulated for the reaction with triphenylsilyl lithium as catalyst. Starting with a, a, a, co, co, co-hexaphenylpolymethylpolysilane, the reaction yields polysilyl lithium compounds and may be represented by the equation ... 

Polyhalogen compounds of methane react with triphenylsilyl lithium to form hexaphenyldisilane and the expected compounds do not occur175-177). 

The effects of additional bonding on the Si—Si framework in reactions of tris(trimethylsilyl)silyl lithium have been investigated by Gilman and Smith219 and no essential differences from triphenylsilyl lithium could be found. 

Triphenylsilyl lithium is then reformed and can react with new starting material. 

Silyl arsines are normally made from alkali metal arsenides and the chlorosilane. However the first ones to be prepared, (Ph3Si)2AsMe, Ph3SiAsMe2 and Ph3SiAsEt2, were obtained from the coupling of triphenylsilyl lithium and the bromoarsine103. They are... 

Very few arsenicals of this type are known. Maier 291) has found that triphenylsilyl lithium couples with dibromomethylarsine forming CH3 As[Si(C6H5)3]2. Dimethylaminotrimethyltin and diphenylarsine give a nearly quantitative yield of diphenyl(trimethylstannyl)arsine 292). Similar compounds are obtained from trialkyltin halides and the sodium derivative of diphenylarsine 178a). 

On the contrary the triphenylsilyl and triphenylgermyl group seem to have no acidifying effect. Lithiation in this case was neither possible with lithiumdicyclohexylamide plus HMPA nor with n-butyllithium or t-butyllithium plus HMPA. In this context it is noteworthy that bi trimethylsilyl)methane 42a) in contrast to bis(triphenylsilyl)methane reacts with n-butyllithium smoothly to the lithium compound The striking difference is well understandable if assuming in bis(tri-phenylsilyl)methane the resonance formulated in Scheme 52 because this brings a... 

Less reactive silyl metal species such as lithium bis(triphenylsilyl) cuprate react with a variety of acyl chlorides to give the corresponding acyl silanes in moderate to good yields75. Dilithium bis(trimethylsilyl) cyanocuprate is particularly effective for the preparation of sterically hindered acyl silanes (Scheme 8), and appears to provide a good general... 

Triphenylsilyl zirconium and hafnium derivatives have been prepared from the silyl lithium species. Triphenylsilyl bis(cyclopentadienyl) zirconium chloride undergoes carbonyl insertion under pressure of carbon monoxide (100 psi) to give the corresponding acyl zirconium species which, upon treatment with anhydrous hydrogen chloride in a benzene matrix at —196 °C and warming to room temperature, gives rise to formyl triphenylsilane55. 

Reaction of DMSB with triphenylsilyl-substituted oxiranyllithium leads to the formation of an olefinic silanol via sequential (1) coordination to the silicon, (2) Si-C bond migration, and (3) Peterson-type Si-O elimination to furnish the alkene. A pentacoordinate siliconate intermediate is presumably involved in this transformation. Therefore, it was reasonable to expect that addition of a nucleophile (methyllithium or lithium t>-propoxide) to an oxiranyl-substi-tuted SCB, which could generate a similar intermediate, would induce the C-Si bond migration to form the same silacyclopentane. Indeed, this alternative order of addition sequence provides the corresponding silanol with better efficiency (84% yield vs. 44%, Scheme 36). 

Triphenylsilyl ethers are similar in lability to TMS ethers toward basic hydrolysis but they are about 400 times more stable than TMS ethers towards acid hydrolysis. A triphenylsilyl ether group played an important strategic role in the finale of a synthesis of the polyether antibiotic Lonomycin A [Scheme 4.96],154 Model studies of the directed aldol reaction by which the lithium enolate 96.1... 

In a related fashion, certain types of vinylogous amides can be prepared by a modification of this same method, as reported by Suzuki (equations 45 and 46). The triphenylsilyl moiety is essential for this transformation. The corresponding t-butyldimethylsilylacetylene gave the simple acylation product without subsequent Michael addition of the amine. In Ae ring expansion process the use of unmodified lithium acetylide (LiC uCH) lead to the formation of by-products. A similar ring expansion process was reported for a-lactams with formation of five-membered ring vinylogous amides. ... 

Silylmetal compounds react also with epoxides for example, (triphenyl-silyl)lithium and oxirane, its methyl derivative, or styrene oxide afford, after hydrolysis, the corresponding vicinal (triphenylsilyl)alkanols 311... 

The combination of the enhanced s-character of the CH-bond by ring strain together with a strong inductively electron-withdrawing substituent leads to a sufficient acidification for the deprotonation of (S)-2-(trifluoromethyl)oxirane 65 which leads to the chemically and configurationally stable lithium compoimd66 [Eq. (22)] [55]. The latter adds to carbonyl compounds in high yields and also reacts with triphenylsilyl and -stannyl chloride, and as well with methyl iodide with complete retention of stereochemistry in the product 67. 

Examples of alkynyl xenonium tetrafluoroborates are known and are prepared by reaction of lithium acetylides or triphenylsilyl acetylenes with XeF2 and BF3-0(CH3)2 at low temperatures (-78 to -40°C) in CH2CI2 solvent. The known alkynyl derivatives are (CH3)3C—CM2— Xe+BF4, (CH3)3Si-CMC-Xe+BF4 , CH3CH2-CMC-Xe+BFJ, and CH3CH2CH2-CM2-Xe+BF4. All of these species decompose in solution or as solids below 0°C. 

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