Diels-Alder: Z,Z diene

Stereochemistry of the diene

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The stereochemistry of the diene must be taken into account to predict what the products will look like. In the following examples, a different diene will be combined with the same acetylene dicarboxylate dienophile, as there is no stereochemistry in a triple bond.

In the above example, the diene is cis,cis (Z,Z), and so has two sets of substituents-inside and outside. The inside one is the bridging CH2 group, which has to end up on one side of the molecule (in this case, sticking up in the products), while the two green hydrogens are outside and remain so. In the product, they end up below the six-membered ring.

Examples of sterochemistry in trans,trans (E,E) and cis,trans (E,Z) dienes can be found here.