Organic Reactions Volume 4 - Sciencemadness Dot Org

360 ORGANIC REACTIONS
quinone. 357 It seems established 355,358 that this reaction involves the
1,4-addition of the alcohol, rearrangement to the hydroquinone, and
oxidation by a second molecule of quinone. A repetition of this process
gives one mole of 2,5-dialkoxyquinone and two moles of hydroqu none
from two moles of alcohol and three moles of quinone.
By similar condensations a variety of monosubstituted or 2,5-disubstituted
quinones has been prepared. Thiols condense with quinones
on mixing the reactants in ethanol to give mono- or di-substituted quinones
in yields of 21-92.5%. 355 Esters of amino acids 359 react similarly
to give disubstitution products (51-64% yield). Indoles give a conden-
2H2NCH2CO2C2H6
Ethanol
*
1 hr,, 0°
O
J1NHCH2CO2C2HB
OH
H6C2O2CCH2HN^ V OH
O
+ 2
sation involving the beta carbon atom; nearly quantitative yields of
monosubstitution products result. 360 The Condensation of ethyl cyano-
Ethanol
H3Cv ^W. J* 80 min.t 100*'** " » -""^ ^"
H
acetate, cyanoacetamide, or malononitrile with quinone in ammoniacal
ethanol gives the 2,5-disubstituted hydroquinone. 354a ' 361
The most widely used condensation of this type is that with amines.
An extensive study of condensations with aromatic amines has been
made; 358 and, with ethanol as solvent, nearly quantitative yields of
disubstitution products are claimed. The condensation of methylamine
357 Knoevenagel and Biickel, Ber., 34, 3993 (1901).
358 Suida and Suida, Ann., 416, 113 (1918).
359 Fischer and Schrader, Ber., 43, 525 (1910).
360 Mohlau and Redlich, Ber., 44, 3605 (1911).
361 Wood and Cox, Org. Syntheses, 26, 24 (1946).
OH
OH