Answer
In the Diels-Alder reaction, a conjugated diene and a dienophile undergo a concerted cycloaddition to form a six-membered ring. This reaction is highly versatile and can be used to synthesize a wide variety of organic compounds, including many natural products and pharmaceuticals. The reaction is named after its discoverers, Otto Diels and Kurt Alder, who received the Nobel Prize in Chemistry in 1950 for their work.