Intramolecular Diels-Alder reaction


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There is no conjugating group on the alkene to stabilise the transition state by overlap between the orbitals of the conjugating group and the back of the diene - the reaction is only able to occur because it is intramolecular.

Because of this there is no endo effect - the molecule simply folds up in the most sterically favourable way, leading to the trans ring junction. Where the alkene has a conjugating group, the endo product may be formed.

Intramolecular Diels-Alder reactions may, or may not, give endo, exo or a mixture of products.

Be prepared!

G. Brieger and J. N. Bennett, Chem. Rev., 1980, 80, 63–97.