1. The powdered
sodium for this preparation may be prepared as in
Org. Syn. Coll. Vol. I, 1941, 252, or according to the following procedure for
potassium, using
xylene instead of
toluene. (With certain other γ-arylbutyric esters it is better to use
potassium.) Commercial
potassium is cleaned by melting it under
toluene, and 10.4 g. (0.27 mole) of the metal and
150 cc. of dry toluene are placed in a
1-l. flask. After the liquid is heated to boiling on a hot plate, the flask is removed and closed with a
ground-glass stopper carrying a
sealed-on stopcock. Apparatus with interchangeable ground joints is essential. After one shake with the stopcock open to relieve superheating, the stopcock is closed, and the flask is shaken quickly and vigorously to powder the metal. The mixture is allowed to cool undisturbed, and
nitrogen is admitted. The stopper is replaced by a distilling head carrying a
500-cc. flask, into which the
toluene can be decanted. The powdered metal is washed several times with absolute
ether and finally covered with
ether (150 cc.) and converted into the ethoxide with
12.6 g. of alcohol diluted with
150 cc. of ether. Traces of
potassium in the wash liquors are destroyed safely by treatment under reflux with alcohol diluted with
ether.
3.
Ethyl γ-phenylbutyrate is prepared in
85–88 per cent yields by refluxing for three hours a mixture of
50 g. of γ-phenylbutyric acid (p. 499),
150 cc. of alcohol dried over lime, and
5 g. of concentrated sulfuric acid. The ester is isolated by distilling
100 cc. of the alcohol under reduced pressure from a steam bath, diluting the residue with 200 cc. of water, separating, and extracting the aqueous layer twice with
50-cc. portions of ether. The combined ester and
ether layers are dried with
sodium sulfate, the
ether removed, and the residue distilled under diminished pressure; the portion boiling at
144–147°/19 mm. is collected.
6. For the cyclization of the keto esters from γ-naphthylbutyric esters it is advisable to use
80 per cent sulfuric acid, and to heat the mixture, with stirring, at 70–80° for one-half hour.