# What is the synthetic importance of the Diels-Alder reaction?

Well, in the simplest reaction you are making $2 \times C - C$ bonds..........
$\text{Diene + olefin "rarr" 6-membered ring}$
And as you know, the number of $C - C$ bond formation reactions is small indeed. And thus Diels Alder reactions are VERY BIG DEALS. Modern variants of the Diels-Alder reaction have introduced stereocontrol into the reaction, and have also allowed the introduction of heteroatoms.