First Synthesis and Isolation of the E- and Z-Isomers of Some New Schiff Bases. Reactions of 6-Azido-5-Formyl-2-Pyridone with Aromatic Amines

Some novel Schiff bases have been prepared by reacting 6-azido-5-formyl-2-pyridone 1 with a series of aromatic amines 2a-f. 5-Arylaminomethylene-6-(E)-aryliminopyridones3a-e were obtained by reaction of 1 with 2a-e at room temperature,whereas with 2f, the 6-azido-5-naphthalen-2-yl-iminomethylpyridone derivative 4 wasformed. On the other hand, heating 1 with 2a-d at 140-150°C yielded two sets of isomericproducts, (E)-3a-d and (Z)-5a-d. Refluxing compounds (Z)-3a,c with hydroxyl-amine inmethanol gave the corresponding hydroxyliminopyridones 8a,c. Heating of (E)-3a-d withexcess POCl3 at reflux did not give the expected tricyclic compound 9, but rather theisomeric products (Z)-5a-d were obtained. The structures of all these products have beencharacterized using IR and 1H- and 13C-NMR spectroscopy.