2-(4-Methoxyphenyl)-1-oxo-1,2-dihydro-1,6-naphthyridine-4-carboxamide (4c) underwent Hofmann rearrangement with iodobenzene diacetate in methanol to give the corresponding 4-amino compound (6c). This, when reacted with 2,4-pentanedione and then hot phosphoryl chloride (attempted Combes synthesis) gave a new heterocyclic system, 6-(4-methoxyphenyl)-2-methylpyrido[3,2-c] pyrrolo[2,3-e]azocin-7(6H)-one (9c). This showed typical pyrrole-type reactivity at the 3-position. Alternatively, an attempt to convert the 4-NH2 in 6c to 4-OH by diazotization gave, instead, a [1,2,3]triazolo[1,5-a]pyridine-3- carboxaldehyde (16c). The same series of reactions on a benzo analog, 2-methyl-1-oxo-1,2-dihydrobenzo[b][1,6]naphthyridine-4-carboxamide (4a), gave the same results.
- Combes product
- Hofmann rearrangement