Answer
Synthesizing dyes is the primary application of the Diels-Alder reaction, which is a cycloaddition reaction between a conjugated diene and a dienophile. This reaction forms a six-membered cyclic compound, and it is widely used in the synthesis of complex organic molecules, including natural products and pharmaceuticals. The Diels-Alder reaction is a powerful tool for constructing carbon-carbon bonds and creating cyclic structures, making it a valuable technique in organic chemistry.