Brønsted-acid and Brønsted-base catalyzed Diels-Alder reactions.

The enantioselective Diels-Alder reaction is one of the most important reactions for the synthesis of complex molecules. It provides access to chiral six-membered carbocyclic compounds containing up to four stereogenic centers in a single step. Asymmetric catalysis in the Diels-Alder reaction has mainly been realized using chiral Lewis acids. In this perspective, we describe several cases of chiral Brønsted-acid and Brønsted-base catalyzed Diels-Alder reactions, providing an overview of this rapidly growing field.