Abstract N-Phenyl-C-chromonyl nitrones 1 and the allenoate zwitterion 2, generated by addition of phosphine to acetylenedicarboxylates, undergo a cascade reaction sequence involving an unprecedented [5+ 3] annulation followed by deoxygenative rearrangement leading to dihydropyridine-fused benzopyrones. Unusual electronic control by the N- substituents of 1 directs the annulation pathway, leading to two different ring-systems.
![2-[(4-oxochromen-3-yl)methylideneamino]phenolate Structure](https://image.chemsrc.com/caspic/017/113326-75-3.png)
![dimethyl 10-oxo-2-phenyl-3,10-dihydro-2H-chromeno[3,2-c]pyridine-3,4-dicarboxylate Structure](https://image.chemsrc.com/caspic/145/1369903-38-7.png)