Synthesis and antibacterial activity of some novel spiro [3H-indole-3,5 '-[1,3,4]oxadiazolo[3,2-c]thiazole]-2(1H)-ones and [1,3,4]oxadiazino[6,5-b]indoles containing 1,8-naphthyridine moiety

Interaction of 2-phenyl-1,8-naphthyridine-3-carboxylic acid hydrazide 1 wit h different isatins 2 gives the corresponding isatin-beta-(2-prenyl-1,8-nap hthyridine-3-carbonylhydrazones) 3. Cyclocondensation of 3 with mercaptoace tic acid in DMF in the presence of anhyd. ZnCl2 affords 3'-(2-phenyl-1,8-na phthyridine-3-carbonylamino)spiro[3H-inole-3,2'-thiazolidine]-2,4' (1H)-dio nes 4, which on treatment with cone. H2SO4 undergo cyclodehydration to furn ish the desired 2'-(2-phenyl-1,8-naphthyridin-3-yl) spiro[3H-indole-3,5'-[1 ,3,4]oxadiazolo[3,2-c]thiazole]-2(1H)-ones 5. On the other hand, the hydraz ones 3 on treatment with cone. H2SO4 leads to-the formation of 2-(2-phenyl- 1,8-naphthyridin-3-yl)-[1,3,4]oxadiazino[6,5-b]indoles 6. The structures of the compounds 3-6 have been established on the basis of their elemental an alyses and spectral (IR, H-1 NMR and mass) data. The compounds 5 and 6 have been screened for their antibacterial activity.