Synthesis of [1,2,4]Triazolo[4″,3″:1′,6′]Pyrimido[4′,5′:3,4]Pyridazino[1,6-D] [1,2,4]Triazine; A Novel Tetracyclic System

Synthesis and Density Functional Theory Study of [1,2,3]Triazolo[4,5-d][1,2,4] Triazolo[4,3-a]Pyrimidine Derivatives: A Novel Heterocyclic System

Several 3H-[1,2,3]triazolo[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives of a novel ring system have been synthesised. The initial substitution of the 4-Cl function of 2,4-dichloro-6-methylpyrimidin-5-amine with benzylamine followed by treatment with sodium nitrite generated 3-benzyl-5-chloro-7-methyl-3H-[1,2,3]triazolo[4,5-d]pyrimidine. Nucleophilic substitution of the 5-Cl moiety of the latter compound with hydrazine hydrate and subsequent treatment with carbon disulfide in boiling pyridine gave, quantitatively, the corresponding [1,2,3]triazolo[4,5-d][1,2,4]triazolo[4,3-a]pyrimidine derivatives. Density functional theory (DFT) studies were also performed to reveal regioselectivity of the ring closure via Gauge-Independent Atomic Orbital (GIAO) 1H NMR calculations. The WP04 method was used as the DFT code to yield accurate chemical shift values. Theoretical results correlated well with the expected regioisomer and aided assignment of the final structure.

Synthesis of Some Derivatives of Pyrimido[5,4-e]Tetrazolo[5,1-c][1,2,4]triazine; a Novel Heterocyclic System

Several new derivatives of pyrimido[5,4-e]tetrazolo[5,1-c][1,2,4]triazine have been synthesised through the reaction of 5-hydrazinyl-1H-tetrazole with 5-bromo-2,4-dichloro-6-methylpyrimidine in CHCl3 solution at ambient conditions. Further treatment of the synthesised compound with secondary amines gave the corresponding substituted heterocycles which were subsequently cyclised into pyrimido[5,4-e] tetrazolo[5,1-c][1,2,4]triazines as derivatives of a novel heterocyclic system on treatment with NaNH2 in CH3CN.