[muddywaters]

Anyone have any ideas on this problem? I can't seem to get the correct dienophile with the corresponding diene.

[orgopete]

I don't agree with the ethylene plus dienophile. That would make the reactant for the Diels Alder reaction to be the product of phthaldehyde and ethylene. If you are only referring to a retro D.A. reaction and no dienophile forming then it is okay. If you are forming a dienophile and diene that actually can undergo a D.A. reaction (as in what give the bicyclic diene undergoing the retro D.A), then the dienophile is going to be acetylene dicarboxaldehyde plus the diene. You can write the corresponding curved arrows that give the diene to identify it.