Organic Reactions Volume 4 - Sciencemadness Dot Org

DIENE SYNTHESIS I 19
CH2 CH3 O
Il I /\
CH CH OC CO
F co Ii co \ /
a > ex > (XK)
XXII XXIII XXIV
1,8-Diphenyloctatetraene adds two molecules of maleic anhydride
smoothly to give a homogeneous adduct (probably XXV). The position
of the double bonds in the central rings was not ascertained. When
reaction is effected in boiling xylene or tetralin a mixture of isomeric
adducts is obtained. Even if only one mole of anhydride is employed,
XXV still is obtained, and unreacted 1,8-diphenyloctatetraene may be
recovered. This would indicate that the monoaddition adduct is more
reactive toward maleic anhydride than is the tetraene itself. The adducts
from 1,4-diphenylbutadiene or 1,8-diphenyloctatetraene are decomposed
into their components upon distillation in vacuum, whereas
the adduct from 1,6-diphenylhexatriene does not dissociate under these
conditions.
Reaction of 1,10-diphenyldecapentaene with maleic anhydride in
boiling xylene yields two isomeric adducts (XXVI, position of double
bonds in cyclohexene rings uncertain) and an amorphous substance.
1,12-Diphenyldodecahexaene combines with three molecules of maleic
anhydride to give an adduct whose structure was not determined conclusively.
Reaction took place similarly with 1,14-diphenyltetradecaheptaene
but no homogeneous adduct was obtained in this instance.
O O O O
OC CO OC CO OC CO OC CO
XXV XXVI
AU the natural polyene pigments are decolorized by addition of maleic
anhydride. The acetate of vitamin A reacts smoothly to give an adduct
(probably XXVII). 169,170 Carotene also reacts with maleic anhydride
169
Hamano, Sd. Papers Inst. Phys. Chem. Research Tokyo, 26, 87 (1935) [C. A., 29,
2545 (1935)].
170
Kawakami, Sd, Papers Inst. Phys. Chem. Research Tokyo, 26, 77 (1935) [C. A., 29,
2545 (1935)].