Organic Reactions Volume 4 - Sciencemadness Dot Org

SYNTHESIS OF BENZOQUINONES BY OXIDATION 339
quinone is obtained from this by hydrolysis and oxidation. This reaction
has been applied extensively. 249-252 Ferric chloride can be used as
Hydrolysis, [O]
> " UOH
the oxidizing agent, 249 ' 250 but oxidation by air in a buffered solution of
pH 8 is usually preferable. 252 The yields by this procedure vary from 78
to 95%, most of them being near 90% (e.g., 2~hydroxy-5-methoxyqui~
none, 2-hydroxy-5,6-dimethoxyquinone, 3-hydroxy-6-methoxytoluquinone,
and 3-hydroxy-5,6-dimethoxytoluquinone). In the acetoxylation
of 3-methoxytoluquinone and 5-methoxytoluquinone substitution occurs
in the position meta to the methoxyl group. 249
OAc
U CH3 Ac2O^ ^NCH3
W CH3ok^JoAc
OAc
Quinones containing a hydroxyl group in the side chain have been
prepared by oxidation of the appropriate O-hydroxychroman or 5-hydroxycoumaran.
Thus, oxidation of 6rhydroxy~2,5,7,8~tetramethyl~
chroman yields 2,3,5-trimethyl-6-(3 , -hydroxybutyl)-quinone. 253 Ferric
O