Triethylamine → 6-chloro-3-(2-fluorophenyl)[1,2,4]triazolo[4,3-b]pyridazine

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Reaction Steps

6-Chloro-3-hydrazinopyridazine (6.9 mmol) was suspended in dioxane (45 mL) with triethylamine (1.1 equiv), and the acyl chloride of 2-fluorobenzoic acid (1.1 equiv) in dioxane (10 ml) was added dropwise over 5-10 min at room temperature. The reaction mixture was stirred at the same temperature for 30-50 min (monitored by TLC), and then the dioxane was removed by rotary evaporation. The residue was refluxed in phosphorus oxychloride (40 ml) for 3-4 hours, and then the solvent was evaporated. 6-Chloro-3-(2-fluorophenyl)-[1,2,4]triazolo[4,3-b]pyridazine was obtained by washing the residue several times with ethyl acetate followed by filtration then adding ice-cold water (50 ml) to the residue. The aqueous layer was neutralized to pH 7 with saturated aqueous sodium hydrogen carbonate, and the resulting solid was collected by filtration, washed twice with water and then with hexane, and dried under vacuum at 50° C. 1H NMR (400 MHz, Me2SO-d6): 8.57 (d, 1H, pyridazine, J=9.3 Hz), 7.85-7.89 (td, 1H, Ph, J=1.6 Hz and 7.4 Hz), 7.68-7.72 (m, 1H, Ph), 7.58 (d, 1H, pyridazine, J=9.4 Hz), 7.45-7.53 (m, 2H, Ph). FABMS (M+H) calculated for C11H6ClFN4.H was 249.0337. found 249.0339.

Provenance & Evidence