A síntese de alguns novos derivados de pirido [1,2-b][1,2,4]triazinas (2-12) foi obtida através da ciclocondensação de 4-aril-1,6-diamino-2-oxo-1,2-diidropiridina-3,5-dicarbonitrilas (1a,b) com compostos α,β-bifuncionais. Foram também preparadas pirido[1,2:2´,3´]triazino[5´,6´-f] triazinas (13) (14). O comportamento de 1a,b frente às interações com indol-2,3-diona e seu análogo N-acetil foi estudado em diferentes condições de reação. As estruturas dos novos produtos foram deduzidas a partir de

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... nálise elementar e de dados espectroscópicos (UV, IR, 1 H RMN, 13 C RMN e espectrometria de massas). Os novos compostos sintetizados foram testados quanto à atividade antifungos. The synthesis of some new pyrido[1,2-b][1,2,4]triazines (2-12) was achieved by cyclocondensation of 4-aryl-1,6-diamino-2-oxo-1,2-dihydropyridine-3,5-dicarbonitriles (1a,b) with α,β-bifunctional compounds. Pyrido[1,2:2´,3´]triazino[5´,6´-f]triazines (13-14) were also prepared. The behavior of 1a,b toward interactions with indole-2,3-dione and its N-acetyl analogue have been studied under different reaction conditions. The structures of the new products have been deduced from elemental analysis and spectral data (UV, IR, 1 H NMR, 13 C NMR and mass spectra). The new synthesized compounds were screened for their antifungal activities. H NMR spectra for compounds 1a,b showed two signals for each compound at 5.6 and 8.4 ppm characteristic for the (N-NH 2 ) and (C-NH 2 ) protons, respectively. These results indicate the difference in nucleophilicity between the two amino groups. Thus, It is expected the hydrazide β-nitrogen (N-NH 2 ) more nucleophilic and would react more rapidly with the electron deficient carbon than the amino group at carbon atom (C-NH 2 ). Mass spectra for compounds 1a and 1b showed the molecular ion peaks at m/z 341 and 285, respectively (the base peaks), indicating the high stability the pyridine moiety. Heterocyclic systems Synthesis, Chemical Reactivity and Fungicidal Activity of Pyrido[1, [1, 2, 4] triazine Derivatives J. Braz. Chem. Soc. 1276 Scheme 1 Scheme 2 Scheme 4