Conditions
Heat. Electron-poor dienophiles (C=C–C=O, C=C–CN) react fastest; the diene must be s-cis.
Mechanism
Red curly arrows show where each pair of electrons moves.
About pericyclic reactions
Pericyclic reactions happen in one step through a cyclic transition state, with electrons moving around a ring. No intermediates form.
Practise this mechanismDraw the curly arrows yourself and Bondline checks each one. Or add it to your notes and watch it in 3D.
Open in Bondline