Org. Synth. 1942, 22, 37
Submitted by C. F. H. Allen and Alan Bell.
Checked by R. L. Shriner and John C. Robinson, Jr..
A solution of 80 g. (0.5 mole) of 1,4-naphthoquinone
[Org. Syntheses Coll. Vol. 1, 375 (1932)
, 383 (1941)
] and 80 g. (1 mole) of 2,3-dimethylbutadiene-1,3 (p. 312)
in 300 ml. of alcohol
is refluxed for 5 hours, using a 1-l. round-bottomed flask
and an efficient reflux condenser
. The solution is cooled and placed in a refrigerator
for 10–12 hours. The crystalline mass is then broken up with a spatula
, and the addition product
is filtered and washed with 50 ml. of cold ethanol
. The product forms white, feathery crystals melting at 147–149° (Note 1)
. The yield is 116 g.
based on the 1,4-naphthoquinone
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).
The addition product is usually pure enough for the next step. It may be purified by recrystallization from acetone
, or methanol
, and then it melts sharply at 150°. If the crude product is deeply colored, it should be recrystallized, using a decolorizing carbon
This is prepared by dissolving 30 g. of potassium hydroxide
in 570 g. of 95% ethanol
The melting points given in the literature vary from 183°1
Essentially the same percentage yield has been obtained using three times the amounts given.
has been obtained by ring closure of the corresponding o-benzoylbenzoic acid
by oxidation of the corresponding anthrone
by decarboxylation of 2,3-dimethylanthraquinone-5-carboxylic acid
from 2-chloro- and 2,3-dichloro-1,4-naphthoquinone
by the action of sodium hydroxide
and from 2-methyl-1,4-naphthoquinone
with subsequent dehydrogenation by sulfur
The addition product employed in the present procedure has been described.8
Chemical Abstracts Nomenclature (Collective Index Number);
2-chloro- and 2,3-dichloro-1,4-naphthoquinone
sodium hydroxide (1310-73-2)
decolorizing carbon (7782-42-5)
potassium hydroxide (1310-58-3)
Anthraquinone, 2,3-dimethyl- (6531-35-7)
o-benzoylbenzoic acid (85-52-9)
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