T-Butyldimethylchlorosilane

The most appropriate silylating reagent for the formation of silyl esters is t-butyldimethylchlorosilane. A preparative example is given in Section 4.2.66, p. 461. Silyl esters are stable in non-aqueous media. 

Diinetiiyl(2,4,<>-tri-f-biitylplienoxy.)dilorasi]ane (1). This silane is suggested as an alternative to the expensive t-butyldimethylchlorosilane. It is more easily prepared (equation I) and is comparable as a silylation reagent. The resulting silyl enol ethers... 

SILYLATION Bis(trimethylsilyl)urea. t-Butyldimethylchlorosilane. t-Butyldimethylsilyl trifluoromethanesulfonate. Chlorotrimethylsilane. Dimethyl(2,4,6-tri-f-butylphenoxy)chlorosilane. Ethyl trimethylsilylacctate. Ketene t-butyldimethylsilyl methyl acetal. N-Methyl-N-(/-... 

Bis[f-butyldimethylsilyl] Tellurium5 A 250 ml, two-necked, round-bottom flask is flame-dried, cooled under an argon atmosphere, and charged with 58 ml (58 mmol) of a 1.0 molar solution of lithium triethylborohy-drjde in tetrahydrofuran. The flask is cooled in an ice bath, 3.56 g (27.9 mmol) of tellurium shot are added, the mixture is warmed to 20°, and stirred for 2h. It is then cooled in an ice bath, 9.74 g (65 mmol) of t-butyldimethylchlorosilane are added, the mixture is stirred at 20" for 2 h, and then heated at 30-60"/ 20 torr to remove all volatile material. The residue is distilled at 5.5 torr yield 7.8 g (79%) b.p. 90-95°/ 5.5 torr m.p. 46-49°. 

Removal of the volatile t-butyldimethylchlorosilane from a mixture of chloro-tris[trifluoromethyl] germane and bis[t-butyldimethyIsilyl] tellurium that had been kept at 80° for two days gave bis[tris(trifluoromethyl)germyl] tellurium in 52% yield. The compound can be stored at — 80° without decomposition5. 

HSiCls and t-PrMgCl results in the formation of /-Pr2SiHCl, but the reaction with t-PrLi gives rise to t-Prs SiH. Preparation of t-butyldimethylchlorosilane from dimethyldichlorosilane requires the use of t-BuLi but an interesting accelerating effect of CN has been observed for the reaction of chlorosilanes with bulky r-BuMgCl. The reaction may proceed through a pentacoordinate intermediate (equation 6). ... 

The literature indicates that f-butyldimethylsilylimi-dazole is probably the most popular reagent for deriva-tizing steroids, and it is often used in conjunction with t-butyldimethylchlorosilane. These reagents form derivatives under relatively mild conditions (room temperature, reaction time, 1 h), reaction goes close to completion, and relatively few side products are generated. 

Cyano-t-butyldimethylsilane. This reagent can be prepared in 75% yield by reaction of t-butyldimethylchlorosilane with KCN in refluxing CH2CI2 catalyzed by 18-crown-6. 

Protection of hydroxyl groups. -2 The /-butyldimethylsilyl (TBDMS) group is recommended for the protection of the 5 -primary hydroxyl groups of nucleosides. For example, the reaction of thymidine (1) with t-butyldimethylchlorosilane in DMF containing imidazole (2.5 molar eq., 1,492-494 2, 220) gives the ether (2) in 60% yield. 

Reaction of t-butyldimethylchlorosilane with ribonucleosides and their 5 -ethers gave access to mono-, di-, and triethers, and optimal conditions for each were developed. Selectivity can be high, so that, for example, 65% of the 2, 5 -diether of uridine can be obtained. The use of these products in oligonucleotide synthesis was discussed. ... 

Lovastatin can be prepared by a fermentation process in the presence of a specific microorganism. Lovastatin can be converted to simvistatin. Hydrolysis of the ester followed by reclosure of the lactone gives the diol. The less-hindered alcohol can be selectively protected using the bulky t-butyldimethylchlorosilane. The free alcohol can be esterified by the acid chloride in the presences of dimethylaminopyridine acylation catalyst. The silyl ether can be selectively removed by treatment with tetrabutyl ammonium fluoride. The fluoride anion reacts at the silicon without hydrolyzing the lactone or ester. 

Alternate Names t-butylcyanodimethylsilane TBDMSCN. Physical Data bp 163-167 °C/760 mmHg mp 76-78 °C. Solubility sol organic solvents (methylene chloride, THF, chloroform) reacts rapidly with water and protic solvents. Preparative Methods conveniently prepared by refluxing t-butyldimethylchlorosilane (1 equiv), potassium cyanide (1.3 equiv) and 18-crown-6 (0.31 equiv) in dry methylene chloride under nitrogen. The reagent can also be prepared by the reaction of silver(I) cyanide with t-butyldimethylchloro-silane, or stirring at 60 °C for 4 h a mixture of sodium cyanide, Amberlite XAD-4 resin, and t-butyldimethylchlorosilane in acetonitrile. ... 

Related Reagents. t-Butyldimethylchlorosilane f-Butyldi-phenylchlorosilane Ethyl 2-(Methyldiphenylsilyl)propanoate. 

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