Cyclohexanecarboxylic acid → 1-(2-Propen-1-yl)cyclohexanecarboxylic acid

Temperatur

-20 °C

300 cm3 of dry tetrahydrofuran (THF) and 40 g of diisopropylamine redistilled over calcium hydride were introduced into a 1 liter three-necked flask fitted with a condenser closed with a calcium chloride guard tube, a low-temperature thermometer, a mechanical stirrer and a nitrogen inlet tube. The solution was cooled to -20° C. and 220 cm3 of a 1.47 M solution of butyl-lithium in hexane were added. The addition was made in the course of 1 hour; the temperature of the mixture was kept at -10° C. 25.5 g (0.2 mole) of 1-cyclohexyl-carboxylic acid, dissolved in 50 cm3 of dry THF, were then introduced in the course of 20 minutes and the temperature of the whole was then raised gradually to 50° C. and this temperature was maintained for 2 hours. The yellow solution was cooled to -70° C. 15.3 g of dry allyl chloride were added and the mixture was stirred for a further 2 hours whilst allowing the temperature to return to ambient temperature, after which the whole was left to stand for 12 hours. The solution was concentrated in vacuo and then poured into 100 cm3 of ice-cold distilled water and 100 cm3 of hexane. The aqueous phase, which had been separated off, was acidified with dilute hydrochloric acid. The 1-allyl-1-cyclohexylcarboxylic acid obtained was extracted with ether. It was purified by distillation under reduced pressure and was in the form of a colourless liquid.