Methyl trimethylsilylacetate

Me3SiCH2C02Et, cat. Bu4N F, 25°, 1-3 h, 90% yield. This reagent combination allows the isolation of pure products under nonaqueous conditions. The reagent also converts aldehydes and ketones to trimethylsilyl enol ethers.The analogous methyl trimethylsilylacetate has also been used. " ... 

The Peterson reaction was reported240 to give a quantitative yield of methyl [(R),(Z)-2-/m-butyldiphenylsiloxymethylcyclobutylidene]acetate on treatment of (5)-2-(ter -butyldiphenyl-siloxymethyl)cyclobutanone with methyl trimethylsilylacetate and lithium dicyclohexylamide. 

A solution of dicyclohexylamine (2.65 g, 14,6 mmol) in THF (20 mL) was treated with 1.66 M BuLi in hexane (8.8 mL, 14.6 mmol) at — 78 °C. The mixture was stirred for 30 min and a solution of methyl trimethylsilylacetate (2.14 g, 14.6 mmol) in THF (10 mL) was added dropwise, and the resulting solution was stirred for another 30 min. The mixture was kept at — 78 °C and a solution of (5)-2-(ferr-butyldiphenyl-siloxymethyl)cyclobutanone (2.42 g, 7.2 mmol) in THF (10 mL) was added dropwise. The reaction mixture was stirred for 1 h and then treated with a pH 7 phosphate buffer. Extraction with EtOAc, washing of the organic phase with brine and drying (Na2S04), followed by evaporation, left a crude material which was purified by column chromatography (silica gel, EtOAc/hexane 1 14) yield 2.82 g (100%). 

Methyl trimethylsilylacetate [2916-76-9] M 146.3, b 65-68 /50mm, d 0.89. Dissolved in Et20, shaken with IM HCI, washed with H2O, aqueous saturated NaHCOj, H2O again, and dried (a ppte may be formed in the NaHCOj soln and should be drawn off and discarded). The solvent is distd off and the residue is fractionated through a good column. IR (CHCI3) v 1728cm . [JOC 32 3535 1967, 45 237 7950]. 

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. ... 

Alternatively, methyl trimethylsilylacetate (3) can be converted to 1 cleanly when trichlorosilyl triflate is used (eq 2). This route has the advantage of not using toxic tin compounds. However, due to the similar boiling point, a complete removal of trimethylsilyl trifluoromethanesulfonate by-product (4) Ifom 1 by Ifactional distillation is difficult. This method is therefore suitable only for use when 4 does not interfere with the subsequent reaction of 1. 

Several routes to j3-lactams, some of which have been discussed earlier, make use of transition metals. For example, reaction of dimethylketene methyl-trimethylsilylacetal (8) with Schiff bases of chiral a-amino-esters in the presence... 

A suggestion has been made that asymmetric induction is possible in cycloaddition reactions leading to azetidinones. The reaction of dimethylketene methyl-trimethylsilylacetal with the Schifl s bases of chiral a-aminoesters in the presence of titanium tetrachloride gave rise to the corresponding /3-lactams with extremely high stereoselectivity. The authors propose the formation of a template (183) between titanium and the Schiff s base leading to stereocontrol (Scheme 24). 

For the addition of an a-silyl carbanion to a carbonyl compound, some reaction models have been put forward that would indicate that the ratio of the resulting fi-silylalkoxide anions is determined by the relative stabilities of the diastereoiso-meric intermediates. This mechanism assumes that the carbanion attacks at 90° to the carbonyl framework [31]. For example, regarding the stereoselective formation of the alkene (Z)-IO by the reaction of an a-silyl carbanion derived from methyl trimethylsilylacetate with 2-alkylcydohexanone 8, the stability of the intermediate yS-silylalkoxide anion 9 is discussed (Scheme 2.9). The trimethylsilyl group occu-... 

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. 

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 ester enolates derived from methyl or t-butyl trimethylsilylacetate react in an analogous manner to ethyl ester (1) with carbonyl compounds. However, with the t-butyl ester the carbonyl reactant has to be an aldehyde as steric problems result in enolization of ketonic substrates. As with the ethyl ester, addition of the enolate to the carbonyl substrate may allow for stereochemical control of the resultant a , -unsaturated ester geometry. In addition, the groups attached to silicon can be modified without substantial changes to the reactivity with carbonyl confounds. ... 

With cyclopentenone derivatives, 1,4-addition is observed for the ester enolates of methyl and f-butyl trimethylsilylacetate, although 1,2-addition occurs with acyclic conjugated enals. With a steroidal cyclopentenone substrate, both 1,2- and 1,4-addition were observed. Conjugate addition is observed for the methyl ester with chiral vinyl sulfoxides. High enantioselectivity can be attained (eq 7). ... 

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. t-Butyl a-Lithiobis(lrimethylsilyl)acetate t-Butyl Trimethylsilylacetate Dilithioacetate Ethyl Bromozin-cacetate Ethyl Lithioacetate Ethyl Lithio(trimethylsilyl)acetate Ketene Bis(trimethylsilyl) Acetal Ketene t-Butyldimethylsilyl Methyl Acetal l-Methoxy-2-trimethylsilyl-l-(trimethylsilyloxy)-ethylene Methyl (Methyldiphenylsilyl)acetate Trimethylsilyl-acetic Acid. 

Related Reagents. r-Butyl Trimethylsilylacetate N,N-T>i-methyl-2-(trimethylsilyl)acetamide Ethyl Lithio(trimethylsilyl)-acetate Ethyl 2-(Methyldiphenylsilyl)propanoate Ethyl Trimethylsilylacetate Lithioacetonitrile... 

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