[74976-84-4]  · C9H18O2Si  · 2-Ethoxycarbonylallyltrimethylsilane  · (MW 186.33)

(2-ethoxycarbonylallylation of aldehydes and acetals; the allylation products are useful precursors to a-methylene-g-butyrolactones;2 precursor of allyl cation equivalents for [3 + 2] and [3 + 4] cycloadditions7,8)

Alternate Name: ethyl 2-(trimethylsilylmethyl)acrylate.

Physical Data: bp 35-40 °C/2 mmHg.

Solubility: sol common organic solvents.

Analysis of Reagent Purity: 1H NMR.

Purification: by distillation.

Preparative Methods: a three-step synthesis from Diethyl Malonate has been reported.2 t-Butyl and trimethylsilyl esters are also prepared by this method. Syntheses from ethyl diethylphosphonoacetate3 and ethyl a-bromoacrylate4 also have been reported, but the simplest procedure involves the reaction of ethoxalyl chloride with two equivalents of Trimethylsilylmethylmagnesium Chloride followed by treatment with Thionyl Chloride (53% yield).5 The CeIII-mediated reaction of trimethylsilylmethylmagnesium chloride with Diethyl Oxalate is also reported to give 2-ethoxycarbonylallyltrimethylsilane in 45% yield.6

Handling, Storage, and Precautions: the reagent can be stored in a glass bottle.

Reaction with Acetals.

The reaction of 2-ethoxycarbonylallyltrimethylsilane (1) with acetals proceeds smoothly in the presence of a Lewis acid such as Titanium(IV) Chloride to afford the corresponding ethoxycarbonylallylation products in good yield (eq 1).2

The resulting homoallyl ethers can be converted to the corresponding a-methylene-g-butyrolactones by dealkylation with Iodotrimethylsilane (eq 2).

Reaction with Aldehydes.

The reaction with aldehydes in the presence of TiCl4 leads to the formation of a-methylene-g-butyrolactones directly but in low yield (eq 3).2

Preparation of 1-Acetoxy-2-trimethylsilylmethyl-2-propene.

Reduction of (1) with Lithium Aluminum Hydride gives 2-trimethylsilylmethylallyl alcohol, which is converted to 1-acetoxy-2-trimethylsilylmethyl-2-propene. When LiAlD4 is used, the dideuterated compound is prepared (eq 4).7 These acetates are used for the palladium-catalyzed cycloaddition with electron-deficient alkenes.

Preparation of Substituted 1-Trimethylsilylmethylallyl Alcohol.

The reaction of (1) with Methyllithium gives 1,1-dimethyl-2-trimethylsilylmethylallyl alcohol (eq 5). The trifluoroacetate derivative is useful for the generation of the 2-trimethylsilylmethylallyl cation (by reaction with Zinc Chloride), which undergoes cycloaddition reactions with dienes.8 The reaction of (1) with the di-Grignard reagent from 1,4-dibromobutane leads to cyclopentanol derivatives that also undergo cyclization reactions with dienes.9

Chain Elongation of Aldonolactones.

2-Ethoxycarbonylallyltrimethylsilane is successfully applied to the chain elongation reactions of monosaccharides.10 The t-butyl ester,2 instead of the ethyl ester, is also used in the reaction (eq 6).

Related Reagents.

3-Acetoxy-2-trimethylsilylmethyl-1-propene; Allyltrimethylsilane; 3-Iodo-2-trimethylsilylmethyl-1-propene.

1. Fieser, M. FF 1982, 10, 55.
2. Hosomi, A.; Hashimoto, H.; Sakurai, H. TL 1980, 21, 951.
3. Kirschleger, B.; Queignec, R. S 1986, 926.
4. (a) Alami, N. E.; Belaud, C.; Villieras, J. TL 1987, 28, 59. (b) Alami, N. E.; Belaud, C.; Villieras, J. JOM 1988 353, 157.
5. Haider, A. S 1985, 271.
6. Lee, T. V.; Channon, J. A.; Cregg, C.; Porter, J. R.; Roden, F. S.; Yeoh, H. T.-L. T 1989, 45, 5877.
7. (a) Trost, B. M.; Chan, D. M. T. JACS 1980, 102, 6359. (b) Trost, B. M.; Chan, D. M. T. JACS 1983, 105, 2326. (c) Trost, B. M. AG(E) 1986, 25, 1.
8. Henning, R.; Hoffmann, H. M. R. TL 1982, 23, 2305.
9. Hoffmann, H. M. R.; Eggert, U.; Gibbels, U.; Giesel, K.; Koch, O.; Lies, R.; Rabe, J. T 1988, 44, 3899.
10. Csuk, R.; Glänzer, B. I. J. Carbohydr. Chem. 1990, 9, 809.

Hideki Sakurai

Tohoku University, Sendai, Japan

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