Organic Reactions Volume 4 - Sciencemadness Dot Org

SYNTHESIS OF BENZOQUINONES BY OXIDATION 359
REFERENCES TO TABLE V
346
Nierenstein, J. Chem. Soc, 111, 8 (1917).
346a
Alcalay, HeIv. Chim. Acta, 30, 578 (1947).
347
Covello, Gdzz. chim. ital., 63, 517 (1933).
348
Covello and Gabrieli, Rend, accad. sci. Napoli (iii), 32, 147 (1926) [C. A.., 22, 1762
(1928)].
349
Pratesi, Gazz. chim. ital., 66, 215 (1936).
350
Dimroth, Kraft, and Aichinger, Ann., 545, 124 (1940).
3BOtt
Nudenberg, Gaddis, and Butz, J. Org. Chem., 8, 500 (1943).
351
Hantzsch and Loewy, Ber., 19, 27 (1886).
352
Thiele and Giinther, Ann., 349, 45 (1906).
353
Covello, Rend, accad. sci. Napoli (iii), 34, 149 (1928) [C. A., 23, 2430 (1929)].
353a
Schubert, J. Am. Chem. Soc, 69, 712 (1947).
354
Bigiavi and Benedetti, Gazz. chim. ital., 54, 363 (1924).
354a Wood, Colburn, Cox, and Garland, J. Am. Chem. Soc, 66, 1540 (1944).
365
Snell and Weissberger, /. Am. Chem. Soc, 61, 450 (1939).
PREPARATIVE METHODS DEPENDING INDIRECTLY UPON OXIDATION
Halogenation of some quinones apparently proceeds by addition to
the double bond and elimination of halogen acid. 79 ' 356 Halogenation of
other quinones, however, involves a dihalohydroquinone as an intermediate.
Halogenation of this latter group of quinones therefore serves
as an indirect route to halogenated quinones since the halohydroquinones
can be oxidized to the corresponding quinones. 3,5-Dibromo-2,6-dimethoxyhydroquinone
is obtained by addition of one mole of bromine
to 2,6-dimethoxyquinone. 287 The hydroquinone can be oxidized to the
quinone by chromic acid, ferric chloride, or a second mole of bromine.
In the preparation of dibromo-oxyloquinone by bromination of o-xylo~
quinone, the dibromohydroquinone is an intermediate. 85
Treatment of quinone with a primary alcohol of low molecular weight
in the presence of zinc chloride gives the 2,5-dialkoxyquinone and hydro-
868 Nef, Am. Chem. J., 12, 463 (1890).
OH OH
< * T)C2H5 OH
O
0