Answer:
Among the compounds occurs a Diels-Alder reaction, which is a pericyclic cycloaddition reaction between a ciclic conjugated diene and an unsaturated compound commonly called dienophile, to form a substituted derivative.
Through the simultaneous construction of two new carbon-carbon bonds, the Diels-Alder reaction provides a reliable way to form rings with good control over regal and stereochemical results.
Explanation: