1,5-Diazabicyclo(4.3.0)non-5-ene → Cyclopropanecarboxylic acid, 3-(2,2-dichloroethenyl)-2,2-dimethyl-, ethyl ester

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Reaction Steps

77 g (0.25 mol) of diethyl 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-1,1-dicarboxylate were dissolved in 300 g of o-xylene and 150 g of 1,5-diaza-bicyclo[4.3.0]non-5-ene were added. The mixture was then heated to the boil for 12 hours. After cooling, the mixture was rendered weakly acid with ice-cold dilute hydrochloric acid. The organic phase was separated off and the aqueous phase was extracted twice more by shaking with methylene chloride. The combined organic phases were washed with sodium chloride solution and then with water and dried with Na2SO4. Fractional distillation gave 36.6 g of ethyl 2,2-dimethyl-3-(2',2'-dichlorovinyl)-cyclopropane-1-carboxylate in the form of a cis/trans mixture in which the trans form greatly predominated.

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