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Diels alder reaction (4+2 cycloaddition reaction) in which diene reacts with dienophile in a supra-supra manner in the heating condition to form the cyclic adduct.

This reaction follows the 鈥渃oncerted mechanism鈥� it is a single-step reaction forming the final cyclic product

The given diene is S-trans for the undergoing Diels-Alder reaction; it has to undergo rotation to form an s-trans conformation.

Diene (s-trans) is drawn such that the ends of its two double bonds are near the dienophile. Then form two single bonds between the diene and the dienophile, convert the three double bonds into single bonds, and convert the former single bond of the diene into a double bond.

The substituents on the dienophile are trans; thus, the cyclic product formed also retains their trans relationship.

Formation of Diels-Alder product