Diels-Alder reactions have emerged as highly powerful transformations for the
generation of structurally complex polycyclic scaffolds essentially due to their associated
rapidity and atom-economy. Since its discovery in 1928, a better understanding of steric and
electronic effects have allowed the development of many different versions including intramolecular
[4+2] cycloadditions, hetero-Diels-Alder reactions, and catalytic asymmetric variants,
among others. In this chapter, we will give an overview on the application of Diels-Alder reactions in Medicinal Chemistry.