Pyrazolo triazino

A heterocyclization involving the N-2 atom of indazole affords [l,2,4]triazino[4,5-h]-indazoles (561) from the 3-carbohydrazinoindazole (78JHC1159,79JHC53). The corresponding pyrazolo[l,5-tf][l,2,4]triazine (562) has been prepared by the same procedure (8UHC1319). 

Nitroquinoline (138) undergoes direct cyclocondensation with aromatic hydra-zones 139 in the presence of sodium hydride in DMF to give low yields of the corresponding [l,2,4]triazino[6,5-fc]quinolines 140 and pyrazolo[3,4-/] quinolines... 

A derivative of 163, 3-(2-morpholinoethylthio)[l,2,4]triazino[5,6-fo]indole dihydrochloride, is used as a thrombolytic (91URP1672373). Derivatives of the pyrazolo[5,l-c][l, 2,4]tria-zines were used as a constituent of silver halide color photographic supported material, which showed good color reproducibility [91JAP(K)03/291649]. The protective action of [l,2,4]triazino[4,3-a]benzimidazoles as corrosion inhibitors was studied (91MI8). 

Pyrazolo[5, l 3,4][l,2,4]triazino[5,6-d]pyrimidine 720 was prepared (89JHC853) by reaction of 716 with formamide. Treatment of 716 with aromatic amines gave 717, whose cyclization with triethyl ortho-... 

Nitroquinoline 209 enters into a direct cyclocondensation with aromatic hydra-zones in NaOH/DMF giving pyrazolo[3,4-/]quinolines 210 and (or) triazino[6,5-/ quinolines 211 in low to moderate yield (Scheme 62) (OOOL413). Their ratio mainly depends on the structure of the starting hydrazone. For example, electron-donating substituents in its aryl moiety assist triazine ring closure. Evidently, pyrazoles 210 are products of two consecutive SNH and SN ipso reactions, whereas conversion of 209 into 211 looks rather complicated and better corresponds with cascade hetero-cyclizations considered in Section III.D.l. 

The reaction of the pyrazolo[5,l-c]-l,2,4-triazine derivative (171) with thiosemicarbazide hydrochloride in acetic acid provided the tricyclic pyrazolo[5, r 3,4]-l,2,4-triazino[6,5-/]-l,3,4-thi-adiazepine (173) (83% yield), via the intermediate (172) (Scheme 31) <89JHC86l>. 

Cyclocondensation takes place on reacting 6-nitroquinoline with substituted hydrazones 69 (Scheme 34) in the presence of NaH in DMF, thus giving rise to 3-aryl-l(3)H-pyrazolo[3,4-f]quinolines 70 and/or 3-aryl[1.2.4]triazino[6,5-f] quinolines 71 [63, 64]. Yields are varied from low to moderate, while the direction of the reaction depends mainly on the structure of hydrazones electron-donating groups in the benzene ring of hydrazones favor the triazine ring formation. 

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