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596 CHAPTER 16 
 
16.65. The starting material is an allylic vinylic ether, so 
it can undergo a Claisen rearrangement. 
 
 
 
Alternatively, we also note that the starting material has 
two C=C bonds that are separated from each other by 
exactly three  bonds, so it can undergo a Cope 
rearrangement: 
 
 
 
We will ultimately end up drawing both processes, and it 
does not matter the order in which we draw these two 
processes. Below, the Claisen rearrangement is drawn 
first, followed by the Cope rearrangement. If instead, the 
Cope rearrangement was drawn first, followed by the 
Claisen rearrangement, the same product would be 
obtained. 
 
 
 
Note that for each of the sigmatropic processes above 
(the Claisen rearrangement and the Cope rearrangement), 
the compound is redrawn in such a way that enables us 
to clearly see the motion of the electrons that cause the 
reaction. You are likely to make a mistake if you try to 
draw the curved arrows without first redrawing the 
structure. That is, avoid doing this: 
 
 
16.66. First we determine the regiochemical outcome. 
The diene is electron-rich, as seen in the second 
resonance structure below: 
 
 
 
And the dienophile is electron-poor, as seen in the third 
resonance structure below: 
 
 
 
These two compounds will join in such a way that the 
electron-poor center lines up with the electron-rich 
center: 
-
+O
O
O
O
O
O
+ En
+
 
 
Notice that the endo product is obtained, rather than the 
exo product, as is expected for Diels-Alder reactions. 
 
16.67. This transformation can be achieved via a retro 
Diels-Alder reaction (shown below), which requires 
elevated temperature, as described in Section 16.7. 
 
 
 
 
 
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