Question

When the diene and dienophile are both unsymmetrical, the Diels-Alder addition may occur in two ways to give two possible regioisomers. (a) Provide the structures of both regioisomers and indicate

which is the major isomer. (b) Explain the regioselective in the formation of the major isomer over the minor one.

Fig: 1

Fig: 2

Fig: 3

Fig: 4