[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.
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).
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
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.
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
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).
Tohoku University, Sendai, Japan