Organic Reactions Volume 4 - Sciencemadness Dot Org

DIENE SYNTHESIS I 17
An interesting variation of the aforementioned Diels-Alder reaction
consists in the replacement of maleic anhydride by fumaryl chloride. 108
Whereas maleic acid gives rise to a cis acid, fumaryl chloride leads to the
corresponding trans acid. The addition of fumaryl chloride to other
dienes is limited, however, by the polymerizing action of this reagent.
Butadiene, for example, is polymerized even when the reaction mixture
is cooled in an acetone-Dry Ice bath.
The following examples illustrate the use of substituted maleic anhydrides
in the synthesis of complex molecules by the Diels-Alder reaction.
H2
OO
/
CO
P +
8,6-endo-MethyIene-3,4,5,6tctrahydrophthalic
anhydride
XJH2
CH
CH
% CH2
CH3O
+ HqCC— CO
H3CC-CO
Pyroclnchonie
anhydride
7-Mcihoxy-3,4-dihydronaphthalene-
1,2-dicarboxyIic anhydride
CH2
CH
^CH
CH2
+ • CH3O
C-Mcthoxy.1,4,9,10,11,12b.cxahydrophcnanthrcne-11,12dicarboxylic
anhydride 169
A novel variation in the Diels-Alder reaction is the substitution of
two molecules of ketene diethylacetal for one of a conjugated diene.
The reaction with maleic anhydride (pyrocinchonic anhydride does not
react) presumably proceeds in the following manner. 160
157 Alder and Backendorf, Ber., 71, 2199 (1938).
158 Woodward and Loftfield, J. Am. Chem. 8oc.} 63, 3167 (1941).
159 Fieser and Hershberg, J. Am. Chem. Soc, 58, 2314 (1936).
160 McElvain and Cohen, /. Am. Chem. Soc, 64, 260 (1942).