Organic Syntheses, CV 3, 310
Submitted by C. F. H. Allen and Alan Bell.
Checked by R. L. Shriner and John C. Robinson, Jr..
1. Procedure
For the dehydrogenation,
40 g. of the addition product is dissolved in
600 ml. of 5% ethanolic potassium hydroxide solution (Note
2) in a
1-l. three-necked flask equipped with a
reflux condenser and inlet tube. A current of air is bubbled through the solution for 24 hours; considerable heat is generated, and the initial green color soon changes to yellow. The yellow
quinone that has separated is then filtered with suction and is washed, first with 200 ml. of water, then with
100 ml. of ethanol, and finally with
50 ml. of ether. The yield of air-dried product (m.p.
209–210°) is
36.5–37.5 g. (
94–96%) (Note
3). The over-all yield for both steps is
90% (Note
4).
2. Notes
1. The addition product is usually pure enough for the next step. It may be purified by recrystallization from
acetone,
ethanol, or
methanol, and then it melts sharply at 150°. If the crude product is deeply colored, it should be recrystallized, using a
decolorizing carbon.
3. The melting points given in the literature vary from 183°
1 to 208°.
2
4. Essentially the same percentage yield has been obtained using three times the amounts given.
3. Discussion
2,3-Dimethylanthraquinone has been obtained by ring closure of the corresponding
o-benzoylbenzoic acid;
1,2,3 by oxidation of the corresponding
anthrone;
4 by decarboxylation of
2,3-dimethylanthraquinone-5-carboxylic acid;
5 from
2-chloro- and 2,3-dichloro-1,4-naphthoquinone and
2,3-dimethylbutadiene-1,3 by the action of
sodium hydroxide;
6 and from
2-methyl-1,4-naphthoquinone and
2,3-dimethylbutadiene-1,3 with subsequent dehydrogenation by
sulfur.
7 The addition product employed in the present procedure has been described.
8
Appendix
Compounds Referenced (Chemical Abstracts Registry Number)
2-chloro- and 2,3-dichloro-1,4-naphthoquinone
ethanol (64-17-5)
methanol (67-56-1)
ether (60-29-7)
sodium hydroxide (1310-73-2)
sulfur (7704-34-9)
Anthrone (90-44-8)
acetone (67-64-1)
decolorizing carbon (7782-42-5)
potassium hydroxide (1310-58-3)
Quinone (106-51-4)
1,4-Naphthoquinone (130-15-4)
2,3-Dimethylanthraquinone,
Anthraquinone, 2,3-dimethyl- (6531-35-7)
2,3-dimethylbutadiene-1,3 (513-81-5)
2,3-dimethylanthraquinone-5-carboxylic acid
2-methyl-1,4-naphthoquinone
o-benzoylbenzoic acid (85-52-9)
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