Diels–Alder reaction
In organic chemistry, the Diels–Alder reaction is a chemical reaction between a conjugated diene and a substituted alkene, commonly termed the dienophile, to form a substituted cyclohexene derivative. It is the prototypical pericyclic reaction with a concerted mechanism; specifically, it is a thermally-allowed [4+2] cycloaddition with Woodward–Hoffmann symbol [π4s + π2s].