New synthetic approaches to condensed pyridazinones: alkylpyridazinyl carbonitriles as building blocks for the synthesis of condensed pyridazinones (original) (raw)
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Tetrahedron, 2013
We hereby report the synthesis of a novel class of compounds, 7-aminofuro-and 7-aminothieno[2,3-d] pyridazin-4(5H)-one and 4-aminophthalazin-1(2H)-ones starting from methyl 2-(2-methoxy-2oxoethyl)furan-and thiophene-3-carboxylate and methyl 2-(2-methoxy-2-oxoethyl)benzoate. The ester functionalities connected directly to the aromatic ring were regiospecifically converted to the acid, whereas methylene groups were oxidized to the corresponding ketoesters. Reaction of the ketoesters with hydrazine provided the hydrazone derivatives. An intramolecular cyclization in the presence of thionyl chloride formed a fused pyridazinone skeleton. Hydrolysis of the remaining ester groups and transformation of the acid functionalities to the acyl azides followed by Curtius rearrangement gave the isocyanates. Reaction of the isocyanates with methanol and water produced urethane and aminopyridazinone derivatives, respectively.
ChemInform, 2003
Condensation of 4-cyano-5,6-dimethyl-3-pyridazinone 1 with aromatic aldehydes gave the novel styryl derivatives 2a-c. Refluxing of compound 2a with phosphorus oxychloride furnished 3-chloropyridazine derivative 3. Compound 3 was reacted with thiourea and produced pyridazine-3(2H)thione 4. Thieno[2,3-c]pyridazines 5a-e were achieved by cycloalkylation of compound 4 with halocompounds in methanol under reflux and in the presence of sodium methoxide. Also, refluxing of compound 4 with N-substituted chloroacetamide in the presence of potassium carbonate afforded thienopyridazines 6a-e. Cyclization of compound 6 with some electrophilic reagents as carbon disulfide and triethyl orthoformate furnished the novel pyrimido[4',5':4,5]thieno[2,3-c]pyridazines 12 and 13a-c, respectively. Diazotisation of compound 6 with sodium nitrite in acetic acid produced the pyridazino[4',3':4,5]thieno[3,2-d][1,2,3]triazines 14a-c. Ternary condensation of compound 1, aromatic aldehydes and malononitrile in ethanol containing piperidine under reflux afforded the novel phthalazines 16a-c. Compound 3 was subjected to some nucleophilic substitution reactions with amines and sodium azide and formed the aminopyridazines 17a, b and tetrazolo[1,5-b]pyridazine 19, respectively. The structures of the synthesized compounds were established by elemental and spectral analyses.
Asian Journal of Chemistry and Pharmaceutical Sciences, 2016
The pyridazinone derivatives, particularly those bearing substituted different group or atom at a different position, have attracted considerable attention due to their characteristic pharmacological and other anticipated activities. These activities promoted the synthesis of a large number of substituted pyridazinone derivatives in order to explore the usefulness of this heterocyclic system. In the present review, various synthetic methods have been studied for the synthesis of substituted pyridazinone derivatives. The behaviour of the pyridazinone toward formaldehyde/piperidine, ethyl chloroacetate, chloroacetic acid, benzene sulfonyl chloride, bromine/acetic acid and aromatic aldehydes has also been studied. However, the reactions of the chloro derivative resulting from the reaction of pyridazinone with phosphorus oxychloride (POCl3). The behavior of chloropyridazine toward hydrazines, thiourea, sodium azide, anthranilic acid, aromatic amines and sulfa compounds have also been ta...
Journal of Chemical Research, 2015
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-1,4dihydropyrimido[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 triazolo[4′′,3′′:1′,6′]pyrimido[4′,5′:3,4]pyridazino[1,6-d ][1,2,4]triazine.
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.