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 (original) (raw)
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Journal of Chemical Research
The condensation reaction of 6-acetyl-3-amino-5-aryl-2-phenyl-2,5-dihydropyridazine-4-carbonitrile with triethyl orthoformate and then with hydrazine hydrate to obtain the new fused bicyclic 4-aryl-5-hydrazinyl-3-(1-hydrazonoethyl)-1-phenyl-1,4-dihydropyrimido[4,5-c]pyridazines via the Dimroth rearrangement is reported. Further cyclisation was achieved by the treatment of latter compounds with triethyl orthoformate to afford several derivatives of a novel tetracyclic fused system [1,2,4] triazolo[4′′,3′′:1′,6′]pyrimido[4′,5′:3,4]pyridazino[1,6-d][1,2,4]triazine.
HETEROCYCLES, 2009
Coupling of E-1-(1-methylbenzimidazol-2-yl)-3-(N,Ndimethylamino)prop-2-enone (1) with the arenediazonium salt gave hydrazonopropanal 5 which underwent cyclocondensation with active methylene compounds to afford substituted pyridazin-6-imine 8 and 11. The enaminone 1 coupled also with the diazonium salts prepared from aminopyrazole, aminotriazole and 2-amino-1H-benzimidazole to afford pyrazolo[5,1-c]-l,2,4triazine 15, 1,2,4-triazolo[5,1-c]-1,2,4-triazine 19, 1,2,4-triazino[4,3a]benzimidazole 23 derivatives, respectively.
A novel synthesis of N1-(substituted)-pyrimido[5,4-e]-1,2,4-triazine-5,7(1H,6H)-diones
Tetrahedron Letters, 2009
A new synthesis of N 1 -(substituted)-pyrimido[5,4-e]-1,2,4-triazine-5,7(1H,6H)-diones, which are analogues of the natural product toxoflavin, is reported. Condensation of preformed alkyl or aryl hydrazones with 6-chloro-3-methyl-5-nitrouracil efficiently provides pyrimidotriazinediones in a three-step process that broadens the scope of R 1 substituents.
Tetrahedron Letters, 2006
Triazolopyridines are an important class of biologically active heterocyclic compounds. In this letter, we describe a new method for the synthesis of [1,2,4]triazolo[4,3-a]pyridines starting from 2-hydrazinopyridine and carboxylic acids. The resulting acetohydrazides are cyclized in a key step using the Lawesson's reagent. The reaction conditions were explored, as well as the scope of this reaction concerning the substituent in position 3 of the triazolopyridine ring. We also demonstrated that this heterocyclization is racemization free in the presence of a chiral carbon in position a to the heterocycle.
Novel Ring Systems: Spiro[Cycloalkane] Derivatives of Triazolo- and Tetrazolo-Pyridazines
Molecules, 2021
In orderto synthesize new pyridazine derivatives anellated with different nitrogen heterocyclic moieties, spiro[cycloalkane]pyridazinones were transformed into the corresponding thioxo derivatives via a reaction with phosphorus pentasulfide. The reaction of the formed 2,3-diazaspiro[5.5]undec-3-ene-1-thiones with hydrazine provided the corresponding 1-hydrazono-2,3-diazaspiro[5.5]undec-3-ene, whose diazotization led to the desired spiro[cyclohexane-1,8′-tetrazolo[1,5-b]pyridazines. The reaction of dihydropyridazinethiones with benzhydrazide afforded the corresponding 7H-spiro[[1,2,4]triazolo[4,3-b]pyridazin-8,1′-cyclohexanes]. As a result of our work, seven new pyridazinethione intermediates were prepared, which served as starting materials for the synthesis of two kinds of new ring systems: tetrazolo-pyridazines and triazolo-pyridazines. The six new annulated derivatives were characterized by physicochemical parameters. The new N-heterocycles are valuable members of the large famil...
Journal of Chemical Research, 2019
On the basis of 2-benzyl-6-hydroxypyridazin-3(2 H)-one, a series of its novel O-substituted (including 6-(1,3,5-triazin-2-yl)oxy) derivatives is prepared. It is proven that the substitution reactions in the initial compound occur mainly at the oxygen atom of the hydroxy group. On the basis of the obtained oxy-aceto(propane)hydrazides, the corresponding azides and anilides are synthesized. A series of 2-[(1-benzyl-6-oxo-1,6-dihydropyridazin-3-yl)oxy]- N′-(substituted benzylidene)aceto(propane)hydrazides is obtained via the reaction of various aromatic aldehydes with the same hydrazides. Heterocyclization of the latter affords compounds with a combination of pyridazine and 1,3,4-oxadiazole rings in the molecule. The reaction of oxy-acetohydrazide with potassium thiocyanate and a mixture of CS2/KOH leads to potassium salts of 2-{[(1-benzyl-6-oxo-1,6-dihydropyridazin-3-yl)oxy]methyl}hydrazine-1-carbothioamide and 2-{2-[(1-benzyl-6-oxo-1,6-dihydropyridazin-3-yl)oxy]acetyl}hydrazine-1-car...
Molecules, 2010
Arylhydrazonomalononitriles 1a,b react with phenylhydrazine to yield amidrazones 2a,b that cyclize to give 2-aryl-5-phenylhydrazono-2,5-dihydro-[1,2,4]triazine-6-carbonitriles 5a,b upon reaction with dimethylformamide dimethylacetal (DMFDMA). Refluxing 5a,b in glacial acetic acid resulted in the formation of the pyrazolo-1,2,4-triazines 6a,b. Compounds 6a,b were also formed upon treatment of 3amino-4-phenylhydrazono-1-phenyl-2-pyrazolin-5-ones 7a,b with DMFDMA. Reacting these triazinyl arylhydrazononitriles 5a,b with hydroxylamine hydrochloride in ethanolic sodium acetate afforded amidrazones 8a,b that are readily cyclized in refluxing dimethylformamide into [1,2,4]triazino[1,2,3]triazines 10a,b.