Synthesis of Dibenzo [b,h] [1,6] Naphthyridine Derivatives : I

Cyclodehydration of 4-\(m\)-chloroa,nilino-8-methoxyquinoline-3-carboxylic acid (IX) and the corres­ponding 8-hydroxy compound (X) in cone. sulphuric acid yielded 4-inethoxy-7-hydroxy-10-chlorodibenzo [b,h][1,6] naphthyridine (XIV) and 4,7-dihydroxy-10-chlorodibenzo [b,h][1,6] naphthyridine (XV) res­pectively. The assigned structure was confirmed by an unequivocal cyclodehydration of 8-methoxy-4- (2-carboxy 5-chloro) anilinoquinoline (XVI) to (XIV). Treatment with phosphorus oxychioride converted XIV and XV to the corresponding 7-chloro derivatives respectively (XVII and XVIII)