6- Nitroquinoline, cyclocondensation with hydrazones

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. 

Another avenue to condensed 3-aryl-l,2,4-triazino[6,5-/ quinolines is again the Sn process accompanied by cyclocondensation of 6-nitroquinoline with the hydrazones of aromatic aldehydes (Scheme 128) <20000L413, 2002J(P1)696>. 

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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