S(=O)(=O)(O)O.[CH2:6]([O:8][C:9]([C:11]1[CH:12]=[N:13][N:14]([C:17]2[CH:22]=[CH:21][C:20](N)=[C:19]([CH3:24])[N:18]=2)[C:15]=1[CH3:16])=[O:10])[CH3:7].N([O-])=O.[Na+].[I-:29].[K+].C(=O)(O)[O-].[Na+].S([O-])([O-])=O.[Na+].[Na+]>O>[CH2:6]([O:8][C:9]([C:11]1[CH:12]=[N:13][N:14]([C:17]2[CH:22]=[CH:21][C:20]([I:29])=[C:19]([CH3:24])[N:18]=2)[C:15]=1[CH3:16])=[O:10])[CH3:7]
After concentrated sulfuric acid (20 ml) were added to 1-(5-amino-6-methylpyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylic acid ethyl ester (7.8 g) and water (80 ml) at 0° C., sodium nitrite (3.0 g) was added therein in several portions. After stirring for 0.5 hour, potassium iodide (9.96 g) was added in several portions and the mixture was stirred for 2.5 hours at room temperature. A saturated aqueous solution of sodium bicarbonate was added in several portions at 0° C. and then an aqueous solution of sodium sulfite was added and the aqueous solution was extracted with ethyl acetate. The organic layer was washed with water and saturated brine, dried over anhydrous sodium sulfate and concentrated in vacuo. The resulting solid was washed with ethyl acetate and n-hexane to give the titled compound (7.76 g) as a yellow solid.
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