Org. Synth. 1957, 37, 80
Submitted by C. David Gutsche and Hugo H. Peter1
Checked by John C. Sheehan, George H. Buchi, and Dwain M. White.
A 3-l. three-necked flask, equipped with a Dry Ice condenser (Note 1), a sealed Hershberg-type stirrer, and an inlet tube, is set up in a hood and charged with 108 g. (0.75 mole) of α-naphthol (Note 2). The stirrer is started, and to the rapidly stirred flask contents (Note 3) is added 1 l. of liquid ammonia as rapidly as possible (about 5 minutes). When the naphthol has gone into solution (about 10 minutes), 20.8 g. (3.0 g. atoms) of lithium metal (Note 4) is added in small pieces and at such a rate as to prevent the ammonia from refluxing too violently (Note 5). After the addition of the lithium has been completed (about 45 minutes), the solution is stirred for an additional 20 minutes and is then treated with 170 ml. (3.0 moles) of absolute ethanol which is added dropwise over a period of 30–45 minutes (Note 6). The condenser is removed, stirring is continued, and the ammonia is evaporated in a stream of air introduced through the inlet tube. The residue is dissolved in 1 l. of water, and, after the solution has been extracted with two 100-ml. portions of ether, it is carefully acidified with concentrated hydrochloric acid. The product formed is taken into ether with three 250-ml. extractions, and then the ether extract is washed with water and dried over anhydrous sodium sulfate. The ether is removed by evaporation to yield 106–108 g. (97–99%) of crude 5,8-dihydro-1-naphthol, m.p. 69–72°. This material is dissolved in 250 ml. of ethyl acetate and hydrogenated with 3.0 g. of 10% palladium on charcoal catalyst (Note 7) at 2–3. atm. pressure in a Parr apparatus until the theoretical amount of hydrogen has been absorbed (about 45 minutes). The catalyst is removed by filtration, and the solvent is removed by distillation to leave 105–107 g. of an oil which quickly solidifies, m.p. 67–69.5°. Recrystallization from 250 ml. of petroleum ether (b.p. 88–98°) gives 93–97 g. (84–88%) of almost colorless crystals, m.p. 68–68.5°.
A cold-finger type of condenser approximately 10 × 40 cm. is satisfactory.
Eastman's white label grade α-naphthol
or equivalent is the most satisfactory starting material. Technical grade α-naphthol
may be used, but it gives an inferior product that is difficult to purify.
Rapid stirring during the addition of the ammonia
is necessary to prevent the formation of a hard cake and resultant interference with the stirrer.
Lithium metal strip (Metalloy Corporation, Rand Tower, Minneapolis, Minnesota)
is wiped to remove the protective grease and then placed in petroleum ether
). Pieces are cut with scissors, air-dried to remove solvent, and added to the reaction mixture.
During the addition of the lithium
the solution turns deep blue. After this has occurred (after about one-third of the lithium
has been added), the rate of addition can be increased considerably.
Toward the end of the addition of the alcohol, foaming may occur but may be subdued by reducing the rate of stirring.
has been prepared by sodium
and reduction of α-naphthylamine
followed by diazotization and hydrolysis;2,3
and amyl alcohol 4,5,6
reduction of α-naphthol
; by sulfonation of tetralin
followed by sodium hydroxide
and by catalytic reduction of α-naphthol
has been prepared by reduction of α-naphthol
and with sodium
The use of lithium
in related systems has been investigated and provides the basis for the preparation described.12
This preparation is referenced from:
Chemical Abstracts Nomenclature (Collective Index Number);
hydrochloric acid (7647-01-0)
ethyl acetate (141-78-6)
sodium hydroxide (1310-73-2)
sodium sulfate (7757-82-6)
amyl alcohol (71-41-0)
1-Naphthol, 5,6,7,8-tetrahydro- (529-35-1)
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