Synthesis of indolo[2′,3′:5,6][1,2,4]triazino[4,3-a][1,8]-naphthyridines and 3′-(3-phenyl-1,8-naphthyridin-2-ylamino)spiro-[3H-3,2′-thiazolidine]-2,4′(1H)-diones as potential antibacterial agents

Condensation of 2-hydrazino-3-phenyl-1,8-naphthyridine 4 with different isatins 5 gives 2-(3-phenyl-1,8-naphthyridin-2-ylhydrazono)-2-indolinones 6, which on cyclization with POCl3 under reflux result in the formation of 7-phenylindolo[2', 3' : 5, 6][1, 2, 4]triazino[4,3-a][1, 8]naphthyridines 7. The hydrazones 6 on treatment with mercaptoacetic acid in DMF in the presence of anhyd. ZnCl2 afford 3'-(3-phenyl-1, 8-naphthyridin-2-ylamino)spiro [3H-indole-3, 2' -thiazolidine]-2, 4' (1H)-diones 8. The structures of the compounds 6-8 have been established on the basis of their elemental analyses and spectral (IR, H-1 NMR and mass) data and evaluated for their antibacterial activity.