Cycloaddition is a chemical reaction where two or more unsaturated molecules combine to form a cyclic structure. This process typically involves the formation of new bonds, resulting in a ring-shaped compound. Cycloaddition reactions are important in organic chemistry and are often used to create complex molecules found in natural products and pharmaceuticals. One common type of cycloaddition is the Diels-Alder reaction, which involves a diene and a dienophile. This reaction is valuable for synthesizing six-membered rings and is widely utilized in the development of various organic compounds. Cycloaddition plays a crucial role in the design of new materials and drugs.