dienophile

A dienophile is a molecule that reacts as the dienophile in a Diels-Alder reaction, a concerted [4+2] cycloaddition that forms a cyclohexene ring. The dienophile must contain a multiple bond, typically a double or triple bond, that can participate in the cycloaddition, and is often made more reactive by electron-withdrawing substituents such as carbonyl or nitrile groups.

In a Diels-Alder reaction, the diene and the dienophile combine to give a single, stereospecific product. The reaction proceeds with suprafacial addition on both components, and when the dienophile bears electron-withdrawing substituents, secondary orbital interactions often favor the endo adduct. The configuration of newly formed stereocenters is controlled by the approach of the two reactants.

Common dienophiles include maleic anhydride, maleimide, acrylonitrile, and norbornene. These species possess relatively low-lying LUMO energies, which align well with the HOMO of many dienes and promote rapid cycloaddition. Electron-withdrawing groups on the dienophile lower LUMO energy and accelerate the reaction, whereas electron-donating groups can reduce reactivity.

The Diels-Alder reaction with a dienophile yields cyclohexene derivatives bearing two new carbon–carbon bonds and defined stereochemistry. This transformation is widely used in organic synthesis to construct six-membered rings and complex polycyclic structures, contributing to natural product synthesis and the development of synthetic routes to various biologically active compounds.