Stereochemistry of the diene

It is possible for the diene to be either 'cis-cis', 'cis-trans' (two possibilities if the diene is unsymmetrical) or 'trans-trans'. 'Click' the images below to view 3D animations of the reactions, all of which use the same simple dienophile which has no stereochemistry:




J. Sauer, Angew. Chemie Int. Ed. English, 1967, 6, 16–33.