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I wonder if I predicted the products correctly, because it seems to be messier than I thought - there's a pair of diastereomers... Also, I feel that the endo/exo rule does not apply here. Am I correct in my understanding? I have never seen a reaction like the one I drawn mentioned anywhere before. Hopefully someone can help me out.Thanks!

Note, there's an example in Clayden reacting cis, trans diene with DEAD, but since there's no stereocenter at nitrogen we end up just getting trans product.

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    $\begingroup$ With fumaronitrile, when one cyano group is endo the other is exo. When the E end of the diene is endo in the TS, the Z end is exo. Then there is also Z-endo and E-exo. So two racemic diastereomers may be expected. $\endgroup$
    – user55119
    Apr 11, 2020 at 22:30

1 Answer 1


Macrophage: I thought you did a fine job in analyzing the Diels-Alder reaction of the E,Z-pentadiene with fumaronitrile. To complement my comment above, I offer an illustration of the transition states of the two reactions leading to their respective products. Because fumaronitrile may add with equal facility (mirror image transition states) to either face of the achiral diene, both 2 and 4 are necessarily racemic. "Racemic" transition states represented by 1 are E-endo/Z-exo that afford racemic bis-nitrile 2. Alternatively, "racemic" transition state 3 is E-exo/Z-endo, which leads to bis-nitrile 4 as a racemate.

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