Organic Reactions Volume 4 - Sciencemadness Dot Org

20 ORGANIC REACTIONS
but yields an adduct whose absorption spectrum shows no remaining
double linkings. 171 An addition product of maleic anhydride with the
methyl ester of bixin has been isolated as a crystalline sodium salt, but
its structure has not been ascertained. 108 The extension of the Diels-
Alder reaction to the natural carotenoids apparently is rendered difficult
by the multiplicity of possible stereoisomers.
CH3 CH3
O O
/ \ / \
OC CO OC CO
CH3 CH3 CH3
XXVII
OH2OCOCH3
Conjugated systems containing a triple bond as well as double bonds
have been made to undergo the Diels-Alder reaction. 2,5-Dimethyll,5~hexadien~3~yne
(XXVIII) adds two molecules of maleic anhydride
to yield the hydronaphthalene derivative XXIX. 146 -* Similar reactions
have provided syntheses of phenanthrene, 172 ' 173 chrysene, 174 ' 175 and 1,2cyclopentenophenanthrene
175, m nuclei.
CR C-CH3 CHC0
h + 2} >
CHCO
XXVIH
Acyclic diene systems containing nitrogen 177 or oxygen do not appear to
undergo normal Diels-Alder reactions. 2-Ethyl-2~hexenalaniline (XXX)
adds maleic anhydride, but the reaction apparently involves an aldimineeneamine
tautomerism. 178 - 179
* Compare Blomquist and Marvel, J. Am. Chem. Soc, 55, 1655 (1933).
m
Nakamiya, Bull. Inst. Phys. Chem. Research Tokyo, 15, 286 (1936) [C. A., 31, 4984
(1937)].
172
Dane, Hoss, Bindseil, and Schmitt, Ann., 532, 39 (1937).
173
Dane, Hoss, Eder, Schmitt, and Schon, Ann., 536, 183 (1938).
174
Joshel, Butz, and Feldman, J. Am. Chem. Soc, 63, 3348 (1941).
175
Butz and Joshel, /. Am. Chem. Soc, 64, 1311 (1942).
176
Butz and Joshel, /. Am. Chem. Soc, 63, 3344 (1941).
177
van Alphen, Rec. trav. chim., 61, 895 (1942) [C. A., 38, 5824 (1944)].
178
Snyder, Hasbrouck, and Richardson, J. Am. Chem. Soc, 61, 3558 (1939).
179
Snyder and Robinson, /. Am. Chem. Soc., 63, 3279 (1941).