The Diels-Alder reaction is a chemical process that forms a six-membered ring by combining a diene and a dienophile. The diene is a molecule with two double bonds, while the dienophile typically contains a double bond or a triple bond. This reaction is a type of cycloaddition and is widely used in organic chemistry to create complex structures efficiently. During the reaction, the diene must be in an appropriate conformation to react with the dienophile. The result is a new cyclic compound, often with significant applications in the synthesis of natural products and pharmaceuticals. The Diels-Alder reaction is valued for its ability to create multiple bonds and rings in a single step.