Synthesis of Some Benzo[b][1,6]naphthyridines and Benzo[b][1,7]naphthyridines

Abstract

Pfitzinger (1-benzylpiperidin-4-one with 7-methylisatin) and Friedlander (3-aminopyridine-4-carbaldehyde with 2-methylcyclohexanone) syntheses, respectively, were used to prepare the title 'azaacridines' containing a methyl substituent peri to the central nitrogen. Oxidation of this group gave the corresponding aldehyde and carboxylic acid. In the [1,6] case, especially, the 10-position was also easily oxidized to give acridone analogues. Nitration occurred exclusively in the benzenoid rings.