Dimethyl malonate → 2-Vinylcyclopropane-1,1-dicarboxylic acid monomethyl ester

Beteiligte Stoffe

Reaktionsschritte

In a 100-ml two-necked flask with thermometer, magnet stirrer and CaCl2 tube, 36.8 g (0.2 mole) of 2-vinylcyclopropane-1,1-dicarboxylic acid dimethyl ester, which is accessible 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) were dissolved in 65 ml of methanol and cooled to ca. 5° C. with ice water. 13.3 g (0.2 mole) of KOH were added portionwise to the mixture, so that the temperature did not rise above 15° C. To complete the reaction, stirring was carried out for a further 12 h and the mixture was then concentrated at a rotation evaporator in vacuum (50 mbar) at 50° C. The obtained oil (ca. 43 g) was dissolved in 50 ml of water and adjusted to about pH 2-3 with conc. hydrochloric acid accompanied by cooling. The organic phase was taken up in 100 ml of diethyl ether, the aqueous phase extracted twice more each time with 100 ml of diethyl ether and the combined ether phases dried over anhydrous Na2SO4. The solution was stabilized with 0.01 g of hydroquinone monomethyl ether, concentrated in vacuum and dried in fine vacuum. 28.2 g (83% yield) of a colourless liquid were obtained.

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