Exploring α-chromonyl nitrones as 1,5-dipoles

Article abstract of DOI:10.1055/s-0031-1290070

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. Georg Thieme Verlag Stuttgart - New York.