s-Triazolo[4,3-b]pyridazines and imidazo[4,5-c]pyridazines

8-Amino-s-triazolo[4, 3-b]pyridazine (I), an adenine analog has been prepared by two different routes. Likewise 8-amino-3-phenyl-s-triazolo[4,3-b]pyridazine (V) has been prepared. Both of these compounds have been prepared utilizing 3,4,5-trichloropyridazine and 3,4,6-trichloropyridazine as the starting materials thus interrelating the 3,4,5-and the 3,4,6-series. A variety of other transformations have been carried out.     

One-pot synthesis of imidazo[1,2-b]pyrazole,imidazo[1,2-b]-1,2,4-triazole,imidazo[1,2-a]pyridine,imidazo[1,2-a]pyrimidine,imidazo[1,2-a]benzimidazole,and 1,2,4-triazolo[4,3-a]benzimidazole derivatives

Hydrazonoyl bromides 1a-c react with 5-amino-3-phenyl-1H-pyrazole, 5-amino-1H-1,2,4-triazole, 2-aminopyridine, and 2-aminobenzimidazole to afford the corresponding imidazol[1,2-b]pyrazoles 10, imidazo[1,2-b]-1,2,4-triazoles 11, imidazo[1,2-a]pyridines 16, imidazo[1,2-a]pyrimidines 17, and imidazo[1,2-a]benzimidazoles 20, respectively. Compounds 1a-c reacted also with 2-methylthiobenzimidazole to give 1,2,4-triazolo[4,3-a]benzimidazole derivatives 21. © 1997 John Wiley & Sons, Inc.     

Synthesis of some 6-methoxyimidazo[1,2-b]pyridazines

The synthesis of 6-methoxyimidazo[1,2-b]pyridazine and its 2-methyl analog is reported. Carboxylic acids, esters and quaternary salts derived from this ring system are described and the heterocyclic system is shown to undergo the Mannich reaction. A condensation reaction of the 2-methyl group is reported and nuclear magnetic resonance (nmr) spectra and acidity constants of some imidazo[1,2-b]pyridazines are recorded.     

Syntheses in the pyridazine series. XXX. Protonation and quaternization studies on imidazo[1,2-b] pyridazines and s-triazolo[4,3-b] pyridazines

Sterically unhindered s-triazolo[4,3-b] pyridazines form N₁-methiodides, whereas 3- and/or 8-substituted analogs form a mixture of N₁- and N₂-methiodides. In some cases thermal rearrangement occurred. Imidazo[1,2-b]pyridazines form N₁-methiodides and here also steric interactions were observed as evidenced by the NMR spectra.     

Synthesis of substituted derivatives of imidazo [5, 1-b] benzimidazole

Heating, either molten or in high-boiling solvents, 1-methyl-2-[(N-phenylthiocarbamoyl)amino] (pyrid-4-yl)-methylbenzimidazole, or refluxing with phosphorus oxychloride in benzene acyl derivatives of 1-methyl-2-[(pyrid-4-yl)(amino)]- and 1-methyl-2 [(phenyl)(amino)]-methylbenzimidazoles, gives the corresponding derivatives of the imidazo [5, 1-b] benzimidazole system, hitherto undescribed in the literature.     

Synthesis and investigation of imidazo[1,2-a]imidazole derivatives

The reduction of 1-benzylideneamino-2,5-dialkyl-3,6-diphenylimidazo[1,2-a]imidazoles with zinc in acetic acid gave the corresponding 1H-imidazo[1,2-a]imidazoles, which are oxidized by air oxygen or by irradiation with UV light to give 1H-imidazo[1,2-a]imidazole 7-oxides. The latter were also obtained by the action of nitric acid on 1-amino-2,5-dialkyl-3,6-diphenylimidazo[1,2-a]imidazoles. The UV, IR, PMR, mass, and x-ray electron spectra of the synthesized compounds were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 384–387, March, 1982.In conclusion, the authors thank I. A. Krasavin for providing us with samples of oxides VII and VIII and T. M. Ivanov and R. V. Linko for recording the x-ray electron spectra.     

Synthesis of new 1,2,4-triazolo[4,3-b]pyridazines and related compounds

The synthesis of novel 6-[4-(1H-imidazol-1-yl)phenyl]-1,2,4-triazolo[4,3-b]pyridazines 8a-f and related compounds is described. Although the intermediate hydrazine derivatives 7 and 9 possess good positive inotropic activity, the fused bicyclic pyridazines 8a-f are significantly less potent than the 3(2H)-pyridazinone 5. Compounds 8a-f are potent but nonselective inhibitors of cardiac phosphodiesterase.     

Reactions with heterocyclic amidines VIII. Synthesis of some new imidazo[1,2-b]pyrazole derivatives

The reaction of benzoylacetonitrile (III) , its phenylazo derivative (X) , malononitrile and malononitrile derivatives with ethyl hydrazinoacetate was investigated. All the investigated compounds with the exception of phenylazobenzoylacetonitrile and phenylazomalononitrile afforded 1-ethoxycarbonylmethyl-3-aminopyrazole derivatives when treated with I. Compounds Xa and XVIII afforded imidazoypyrazole derivatives under the same experimental conditions.     

Research on heterocyclic compounds. XXI. Synthesis of imidazo[2,1-b]benzothiazole and imidazo[2,1-b]thiazole derivatives

The reaction of some 2-aminobenzothiazoles and 2-aminothiazoles with ethyl 3-bromo-4-oxopentanoate was investigated with the aim to obtain the corresponding imidazo[2,1-b]benzothiazole and imidazo[2,1-b]-thiazole derivatives, respectively. In some cases, two unexpected side products were obtained together with the required compound and their structures were elucidated: e.g., 2-aminobenzothiazole reacted with ethyl 3-bromo-4-oxopentanoate to give ethyl 2-methylimidazo[2,1-b]benzothiazole-3-acetate together with ethyl imi-dazo[2,1-b]benzothiazole-2-propionate and ethyl 3-(benzothiazol-2-yl)amino-4-oxopentanoate.     

Synthesis and anti-inflammatory activity of imidazo [1,2-a] pyrimidine derivatives

A series of imidazo[1,2-a]pyrimidine derivatives substituted adjacently with two aryls at positions 2 and 3 were designed and synthesized in order to improve their anti-inflammatory activities. Biological tests suggested that these compounds have antiinflammatory activities with COX-2 selectivity to some extent.