What makes maleic anhydride an exceptionally reactive dienophile

Maleic anhydride is also a very good dienophile, because the electron-withdrawing effect of the carbonyl groups causes the two alkene carbons to be electron-poor, and thus a good target for attack by the pi electrons in the diene. … alkyl groups) and electron-withdrawing groups on the dienophile.

Remember that electron-donating groups increase the reactivity of the diene: … Therefore, electron-donating groups on the diene increase its reactivity, while electron-withdrawing groups on the dienophile lower the LUMO energy level, thus support this electron flow as well.