The diene lactone shown in part (a) has one electron-donating group (- OR) and one electron-withdrawing group (C = O). This diene lactone is sufficiently electron-rich to serve as the diene in a Diels-Alder reaction.
(a) What product would you expect to form when this diene reacts with methyl acetylenecarboxylate, a strong dienophile?

(b) The Diels-Alder product A is not very stable. Upon mild heating, it reacts to produce CO2 gas and methyl benzoate (PhCOOCH3), a very stable product. Explain how this strongly exothermic decarboxylation takes place.

Transcribed Image Text:

COOCH3 product A Diels-Alder product (unstable) -→ diene lactone methyl acetylenecarboxylate