Organic Syntheses, CV 4, 898
[I. METHOD A]
Submitted by Cecil E. Olson and Alfred R. Bader
1.
Checked by James Cason, Gerhard J. Fonken, and William G. Dauben.
1. Procedure
A
3-l. three-necked flask is fitted with a
mercury-sealed stirrer, an
efficient condenser capped by a
drying tube filled with calcium chloride, and a
wide-bore rubber tube leading to a
1-l. Erlenmeyer flask.
One liter of dry, thiophene-free benzene and
104 g. (1.21 moles) of γ-butyrolactone (Note
1) are placed in the
3-l. flask.
Six hundred grams (4.5 moles) of reagent grade anhydrous aluminum chloride (Note
2) is placed in the Erlenmeyer flask and is added to the stirred reaction mixture during a period of 2 hours. The mixture becomes dark brown, refluxes gently, and evolves
hydrogen chloride. After addition of all the catalyst, the mixture is heated on a
steam bath with continued stirring for 16 hours. It is then cooled to room temperature and poured onto 3 kg. of crushed ice drenched with
500 ml. of concentrated hydrochloric acid. The lower aqueous layer is separated and extracted with about
500 ml. of toluene. The brown, organic, upper layer and the
toluene extract are combined, washed successively with water,
20% potassium hydroxide solution, and water, and distilled under reduced pressure to remove
benzene,
toluene, and traces of water. Distillation of the residue in a
Claisen flask (Note
3) yields
160–170 g. (
91–96%) of
α-tetralone, b.p.
75–85°/0.3 mm.,
nD25 1.565–1.568 (Note
4) and (Note
5). There is a residue consisting of 130–150 g. of red-purple viscous oil.
2. Notes
1. A
commercial grade of butyrolactone supplied by the General Aniline and Film Corporation, 230 Park Avenue, New York 17, New York, was used by the submitters. The checkers used material from Eastern Chemical Corporation, 34 Spring Street, Newark 2, New Jersey, which was distilled before use, b.p.
208–210°.
3. The checkers distilled the product through a
0.5-meter packed column with heated jacket and partial reflux head. The yield was
148–155 g. (
85–88%), b.p.
143–145°/20 mm.,
nD25 1.5669–1.5671. There was a fore-run of
10–15 g. and an after-run of about
8 g., b.p.
145–180°/20 mm.
4. The submitters state that varying the amounts of
aluminum chloride varied the yields as shown in the table.
|
AlCl3, g. |
α-Tetralone, g. |
Yield, % |
|
400 |
119 |
68 |
500 |
151 |
86 |
600 |
165 |
94 |
700 |
166 |
95 |
|
[II. METHOD B]
Submitted by G. Dana Johnson
2
Checked by James Cason, William G. Dauben, Bradford H. Walker, and Charles E. Stehr.
1. Procedure
In a dry
2-l. three-necked round-bottomed flask, fitted with a gas-tight stirrer and a
reflux condenser carrying at the top a calcium chloride drying tube connected to a gas-absorption
trap (a good
hood is preferable), are placed
98.5 g. (0.6 mole) of γ-phenylbutyric acid3 and
200 ml. of dry thiophene-free benzene (Note
1). After the solution has been cooled, with stirring, for a few minutes in an
ice bath,
125 g. (0.6 mole) of phosphorus pentachloride is added during 5 minutes (Note
2). After the ice bath is removed the contents of the flask are heated during 20 minutes (vigorous evolution of
hydrogen chloride) to the boiling point by means of a
water bath, and refluxing is continued for about 5 minutes. As stirring is continued the flask is cooled in an
ice-salt bath until the internal temperature (Note
3) reaches about −10°. With continued efficient cooling, there is added during 30–40 minutes a solution of
150 ml. (1.28 moles) of anhydrous stannic chloride in
150 ml. of dry thiophene-free benzene (Note
1), as the temperature is maintained below 15°. The reaction is highly exothermic, and
hydrogen chloride is rapidly evolved. Stirring is continued for 1 hour at 0–10°, at the end of which time the
thermometer is replaced by the condenser and the complex is decomposed by careful addition of 300 g. of ice followed by
250 ml. of concentrated hydrochloric acid. This two-phase mixture is heated to reflux, with vigorous stirring, on a water bath for about 25 minutes or until
hydrogen chloride is no longer evolved (Note
4).
The cooled reaction mixture is separated in a
separatory funnel, and the aqueous phase is extracted with three
50-ml. portions of benzene. These extracts are combined with each other but kept separate from the original organic phase; each wash solution is used first with the original organic phase, then the extracts. The washes are 150 ml. of water (Note
4),
100 ml. of 10% sodium carbonate solution, 100 ml. of water, and finally
50 ml. of saturated sodium chloride solution (Note
5). Solvent is distilled from the combined extracts, and the residue is distilled at reduced pressure in a Claisen flask. The yield of
α-tetralone, b.p.
135–137°/ 15 mm.,
n25D 1.5671–1.5672, is
75–80 g. (
85–91%).
2. Notes
1. A total of
350 ml. of dry benzene is required. It may be dried by allowing it to stand for a few days with about 1 g. of
sodium wire, or by slowly distilling about
20% of a lot of benzene and cooling the residue with protection from atmospheric moisture by use of a calcium chloride tube.
2. It is convenient to weigh the
phosphorus pentachloride in an Erlenmeyer flask which is then attached to a side neck of the
three-necked flask by a 6-in. length of wide-bore thin-walled rubber tubing.
3. The condenser is replaced by a thermometer extending into the stirred liquid. The thermometer is inserted through a
wide-bore T-tube whose side outlet is protected by a calcium chloride tube.
4. The
stannic chloride complex is decomposed relatively slowly. Addition of
5–10 ml. of ether facilitates the decomposition. If the decomposition is not completed during the heating period, the wash with water gives a troublesome precipitation of
stannic hydroxide. If this occurs the organic phase should either be heated for 30 minutes with, or allowed to stand overnight with,
100 ml. of 6N hydrochloric acid.
5. The wash with saturated salt solution usually gives a clean separation and removes most of the water from the organic phase. No additional drying is necessary since the remaining water is removed by azeotropic distillation with
benzene.
3. Discussion
Method I is based on the procedure of Truce and Olson.
15
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