Org. Synth. 1938, 18, 24
DOI: 10.15227/orgsyn.018.0024
[1,2-Naphthalenedicarboxylic anhydride, 3,4-dihydro-]
Submitted by E. B. Hershberg and Louis F. Fieser.
Checked by C. R. Noller and S. Kinsman.
1. Procedure
(A) Ester Condensation.—In a 1-l. round-bottomed flask, fitted with a reflux condenser equipped with a dropping funnel and a calcium chloride tube, is placed a suspension of 6.1 g. (0.27 mole) of powdered sodium (Note 1) in 150 cc. of absolute ether. A solution of 12.6 g. (0.27 mole) of absolute ethyl alcohol (Note 2) and 50 cc. of absolute ether is added, and the mixture is allowed to stand overnight to complete the reaction. To the suspension of sodium ethoxide, 57 g. (0.39 mole) of ethyl oxalate (Org. Syn. Coll. Vol. I, 1941, 261), diluted with 50 cc. of ether, is added in portions. After the spontaneous reaction subsides, the pale yellow solution is allowed to stand for one-half hour, and 50 g. (0.26 mole) of ethyl γ-phenylbutyrate (Note 3), diluted with 50 cc. of absolute ether is added. The mixture is refluxed gently for twenty-four hours (Note 4).
The deep red solution is cooled in an ice bath and neutralized by the addition, with shaking, of an ice-cold solution of 15 cc. of concentrated sulfuric acid in 200 cc. of water. The ether layer is separated, washed with water, and dried over sodium sulfate. The ether is removed by dropping the solution from a separatory funnel the stem of which extends to the bottom of an evacuated Claisen flask heated on the steam bath. The residue is a pale yellow oil consisting of a mixture of ethyl α-ethoxalyl-γ-phenylbutyrate and unchanged ethyl oxalate (Note 5).
(B) Cyclization.—The above oil is poured slowly into 500 cc. of concentrated sulfuric acid, the temperature being kept at 20–25° by cooling in an ice bath. After standing for one and one-half hours at 20–25°, the deep red solution is poured on 3 l. of ice and water. The anhydride, precipitated as a pale yellow solid, is collected and washed thoroughly with water. Dried in vacuo at 25°, the material weighs 40–45 g. and melts at 117–122°. Distillation under diminished pressure gives a light yellow product, m.p. 122–124°. The yield is 38–42 g. (73–81 per cent of the theoretical amount). This material is suitable for most purposes. Crystallization from 100 cc. of benzene with the addition of 75 cc. of ligroin (b.p. 60–80°) gives 34–41 g. of pale yellow prisms, m.p. 125–126° (Note 6).
2. Notes
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.
2. The alcohol was dried according to Org. Syn. Coll. Vol. I, 1941, 251, Note 1.
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.
4. With potassium ethoxide the reaction is complete in twelve hours.
5. The keto ester decomposes on distillation, even under diminished pressure.
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.
3. Discussion
The above procedure is a modification1 of the method of von Auwers and Möller.2
This preparation is referenced from:

References and Notes
  1. Fieser and Hershberg, J. Am. Chem. Soc. 57, 1851 (1935).
  2. von Auwers and Möller, J. prakt. Chem. (2) 109, 137 (1925).

Chemical Abstracts Nomenclature (Collective Index Number);
(Registry Number)


ethyl α-ethoxalyl-γ-phenylbutyrate

ethyl alcohol,
alcohol (64-17-5)

sulfuric acid (7664-93-9)

Benzene (71-43-2)

ether (60-29-7)

sodium sulfate (7757-82-6)

nitrogen (7727-37-9)

toluene (108-88-3)

sodium (13966-32-0)

sodium ethoxide (141-52-6)

potassium (7440-09-7)

xylene (106-42-3)

Ethyl oxalate

3,4-Dihydro-1,2-naphthalic anhydride,
1,2-Naphthalenedicarboxylic anhydride, 3,4-dihydro- (37845-14-0)

ethyl γ-phenylbutyrate (10031-93-3)

γ-Phenylbutyric acid (1821-12-1)

potassium ethoxide (917-58-8)