Hebucol,Logeais,France,1957
Into a balloon flask with two lateral necks furnished with an efficient
mechanical agitator and protected from moisture by a calcium chloride guard,
there are introduced 12 g (0.185 mol) of pure powdered zinc and 20 ml of a
solution of 16.6 g (0.17 mol) of anhydrous cyclohexanone and 31.5 g (0.16
mol) of ethyl α-bromobutyrate in 25 ml of anhydrous benzene. With vigorous
stirring in a manner to put the zinc into suspension, the balloon flask is
gradually heated in an oil bath to 100°C to 105°C. After a few minutes, a
reaction starts, causing violent boiling which is maintained while adding the
balance of the reactants. Boiling is then continued for one hour. After cooling,
the reaction mixture is turned into a beaker containing 30 ml of sulfuric acid
to half (by volume) with ice. After agitation, the mixture is decanted into a
container for separation. The aqueous phase is reextracted with benzene. The
pooled benzene solutions are washed with dilute (10%) cold sulfuric acid, then
with cold sodium carbonate (5%) and then with ice water, and dried over
anhydrous sodium sulfate. The benzene is evaporated and the ester, which is
ethyl α(hydroxy-1-cyclohexyl) butyrate, is distilled off under reduced pressure.
The yield obtained was 17 to 19 g or 49% to 55%.
The ester was saponified with baryta in aqueous methanol as follows:
21.5 g (0.1 mol) of the above ethyl ester is saponified by boiling under reflux
for 4 hours, while agitating, with 30 g (0.095 mol) of barium oxide hydrated
to 8H2O in 250 ml of a mixture of equal volumes of methanol and water. After
concentration to one-half its volume under reduced pressure and filtration, the
aqueous solution is washed with ether and then acidified at 0°C with 10%
hydrochloric acid. The acid liberated in oily form is extracted with ether. The
ether is washed with water, dried and evaporated. The yield is 75-80% (14-15
g of crude acid) which crystallizes spontaneously little by little. It can be
crystallized in a mixture of ether and petroleum ether (1:10) or, with better
yield, in light gasoline or oil (solubility of the pure acid ranges from 0.3% at
0°C to 100% at the boiling point). The yield of crystals is 75-80%. The
α(hydroxy-1-cyclohexyl) butyric acid thus obtained is a colorless crystalline
product with a melting point of 81°C to 82°C.
