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The Nobel Prize-winning Diels-Alder reaction, named after Otto Paul Hermann Diels and Kurt Alder, is a chemical reaction between a conjugated diene and a substituted alkene, resulting in the formation of a cyclic compound. The reaction involves a concerted cycloaddition mechanism, where both new bonds are formed simultaneously. The reaction is widely used in organic synthesis for the construction of various cyclic compounds, including six-membered rings.