[nikienikie]

Hi all!

So The Diels-Alder reaction favors an Endo addition. And my book says, "the product in which the activating electron-withdrawing group of the dienophile is located in the endo position."

What is an "endo position"? Does it just mean the electron withdrawing group is facing the the diene? What if my dienophile is dimethyl fumarate? Since the two groups are on the opposite side of the alkene, one of them is exo and the other one is endo?

Thank you!!

[Hunter2]

Check endo and exo positions

http://en.wikipedia.org/wiki/Endo-exo_isomerism

[james_a]

Hi all!

So The Diels-Alder reaction favors an Endo addition. And my book says, "the product in which the activating electron-withdrawing group of the dienophile is located in the endo position."

What is an "endo position"? Does it just mean the electron withdrawing group is facing the the diene? What if my dienophile is dimethyl fumarate? Since the two groups are on the opposite side of the alkene, one of them is exo and the other one is endo?

Thank you!!

With some dienophiles endo/exo is not possible.  With fumarate as dienophile you will see that it's not possible to form diastereomers; either way, you always obtain groups on opposite sites of the ring. Contrast that with maleate, which would give you endo and exo.

[PhDoc]

The Alder Endo Rule explains the stereochemical outcome of most (not all) Diels-Alder reactions. The endo preference has to do with secondary orbital overlap, and the resultant lowering of transition state energy.

The Diels-Alder Reaction, Part I
http://lennoxtutoring.com/2011/11/23/the-diels-alder-reaction-part-one/

I provide a model system to make determining the relative stereochemistry predictable without the use of silly rules. If you have interest in more advanced applications of the Diels-Alder, search my website for Part II.

Good luck!

[orgopete]

I provide a model system to make determining the relative stereochemistry predictable without the use of silly rules.