Silylations ethyl trimethylsilylacetate

SILYLATION Ethyl trimethylsilylacetate. Trimethylsilyl trifluoromethanesul-fonate. 

Silylation of acidic compounds.2 The combination of ethyl trimethylsilylacetate and 2-5 mole % of tetra-n-butylammonium fluoride (TBAF) is a markedly efficient reagent for transfer of trimethylsilyl groups to relatively acidic substrates such as ketones, alcohols, thiols, phenols, and carboxylic acids, and even 1-alkynes. KOCH3/ (18-crown-6) and Triton B are also effective catalysts. 

SILYLATION OF KETONES WITH ETHYL TRIMETHYLSILYLACETATE (Z)-3-TRIMETH YLSILOX Y-2-PENTENE... 

Ethyl trimethylsilylacetate is stable to the usual manipulations, and can be stored in glass containers for years without change of physical and spectral properties IR (liquid film) cm 1720, characteristic of a-silyl esters The reported physical constants are bp 16-lTC (40 mm),... 

The introduction of the trimethylsilyl chloride trapping technique" led to improved yields in the case of simple aliphatic esters. The initial silylated products are easily isolated and can be converted into the acyloins simply and in high yield. For simple aliphatic esters the yields are in the range 56-92%. Use of trimethylsilyl esters, rather than simple alkyl esters, leads to faster reactions, but lower yields.Substituted esters which have been successfully used in the newer procedure include ethyl 2-ethylhexanoate (83%), ethyl trimethylsilylacetate (90%)," ethyl 3-trimethylsilylpropionate (65%)," ethyl phenylacetate (48%)," ethyl 3-phenylpropionate (79%)" and 2-(2-methoxycarbonylethyl)-2-methyl-l,3-dioxolane derived from levulinic acid (65%)." In the case of ethyl adamantane-l-carboxylate the yield using the newer procedure is reported to be inferior to that using the earlier procedure. 

SUylation. Alcohols and ketones are silylated in high yield by ethyl trimethylsilylacetate with catalysis by tetra-n-butylammonium fluoride (sensitive to moisture) as base. The side product is the volatile ethyl acetate (equation I). 

Dimethylfoimamide. Lithium diisupiupylamide. p-Toluene sulfonyUiydrazine. SILYLATION N,0-Bis(trimethyl iIyl) ulfonate. Ethyl trimethylsilylacetate. Trifluoro-methanesulfonic add trimethylsilyl ester. N-(Trimethylsilyl)imidazole. SPIROCYCLIZATION Pyriolidine. 

Related Reagents. f-Butyl a-Lithiobis(trimethylsilyl)acetate f-Butyl Trimethylsilylacetate Ethyl Bromozincacetate Ethyl Lithioacetate Ethyl Trimethylsilylacetate Ketene Bis(trimethyl-silyl) Acetal Ketene f-Butyldimethylsilyl Methyl Acetal l-Methoxy-2-trimethylsilyl-l-(trimethylsilyloxy)ethylene Methyl (Methyldiphenylsilyl)acetate Methyl 2-Trimethylsilyl-acrylate Triethyl Phosphonoacetate Trimethylsilylacetic Acid. 

Related Reagents. f-Butyl Trimethylsilylacetate Dimethyl-2-(trimethylsilyl)acetamide Ethyl (Methyldiphenyl-silyl)acetate Ethyl Trimethylsilylacetate Trimethylsilylacetic Acid Trimethylsilylacetone. 

Related Reagents. r-Butyl Trimethylsilylacetate NJ -Dimethyl-2-(trimethylsilyl)acetamide Ethyl 2-(Methyldiphenyl-silyl)propanoate Ethyl Trimethylsilylacetate Trimethylsilyl-acetic Acid. 

A mixture of acetophenone and ethyl trimethylsilylacetate added with the aid of a hypodermic syringe at 0° under argon to tetra-n-butylammonium fluoride, stirred 1-3 hrs. at room temp., the volatiles removed, dil. with n-hexane, filtered, and distilled product. Y 98%. F. e., also silylation of alcohols, and regio-specificity, s. E. Nakamura et al., Am. Soc. 98, 2346 (1976). 

Trimethylsilylacetate esters may he converted to the enolate by treatment with lithium dialkylamide bases (LDA in Eq. 7.28) in THF at -78°C. These will add to ketones or aldehydes quickly at -78°C, followed by elimination of MOjSiOLi and formation of a,p-unsaturated esters in high yields, uncontaminated by p,y-unsaturated isomers [47]. This is known as the Peterson reaction [48, 49]. The requisite ethyl trimethylsilylacetate is made by the reaction of cldorotrimethylsilane, ethyl bromoacetate, and zinc [50]. Esters of longer-chain acids give mostly 0-silylation under these conditions, but diphenylmethylchlorosilane gives C-silylation selectively. These diphenyl-methylsilylated esters also give the Peterson reaction (Eq. 7.29) [51]. 

Preparative Methods an advantage of f-butyl trimethylsilylacetate over its methyl and ethyl ester analogs is that it can be prepared by C-silylation of the lithium enolate of f-butyl acetate at —78 °C in THF (85-90% yield). Under the same conditions the enolates of methyl and ethyl acetate give primarily 0-silylated products. The reagent has also been prepared by a rapid boron trifluoride etherate catalyzed reaction of trimethylsilylketene with f-butyl alcohol. ... 

Analogs. The methyl ester (2) undergoes similar reactions to the ethyl ester (1), as do various silyl analogs. These reactions also include silylations with methyl trimethylsilylacetate in the presence of fluoride ion. ... 

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