Hydrochloric Acid → 2-Vinylcyclopropane-1,1-dicarboxylic acid monomethyl ester

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Reaction Steps

36.8 g (0.2 mol) of 2-vinyl cyclopropane-1,1-dicarboxylic acid dimethyl ester, obtainable from malonic acid dimethyl ester and trans-1,4-dibromobut-2-ene (cf U.S. Pat. No. 4,713,478 and U.S. Pat. No. 4,713,479), are dissolved in 65 ml of methanol in a 100 ml two-necked flask with a thermometer, magnetic stirrer and CaCl2 tube, and the solution is cooled to ca 50° C. with iced water. Then 13.3 g (0.2 mol) of KOH are added in portions in such a way that the temperature does not rise above 15° C. In order to complete the reaction, stirring is continued for 12 hours, and then volatile components are removed in a rotary evaporator in vacuo (50 mbar) at 50° C. The oil obtained (ca 43 g) is dissolved in 50 ml of water and is adjusted to a pH of ca 2-3 with concentrated hydrochloric acid accompanied by cooling. The organic phase is taken up in 100 ml of diethyl ether, extracted twice more with in each case 100 ml of diethyl ether, and the combined ether phases are dried over anhydrous Na2SO4. The solution is stabilized with 0.01 g of hydroquinone monomethyl ether, concentrated in vacuo and dried under a medium high vacuum. The result is 28.2 g (83% yield) of a colourless liquid.

Provenance & Evidence