[CH3:1][N:2]1[C:6]([C:7](O)=[O:8])=[CH:5][C:4]([CH3:10])=[N:3]1.C(N(CC)CC)C.C(OC(Cl)=O)C.[N-:24]=[N+:25]=[N-:26].[Na+]>CC(C)=O.O>[N:24]([C:7]([C:6]1[N:2]([CH3:1])[N:3]=[C:4]([CH3:10])[CH:5]=1)=[O:8])=[N+:25]=[N-:26]
To a solution of 1,3-dimethylpyrazol-5-carboxylic acid (500 mg, 3.57 mmol) in a mixture of acetone (10 mL) and water (5 mL) was added triethylamine (0.75 mL, 7.13 mmol). The mixture was cooled to 0° C. in a ice-bath. Ethylchloroformate (774 mg, 7.13 mmol) was then added and the resulting mixture was stirred for 1.5 hours at 0° C. To the mixture was added sodium azide (0.844 g, 13.0 mmol), and the mixture was stirred for another 1.5 hours. The mixture was concentrated, the residue was diluted with dichloromethane and washed with water. The organic layer was dried over MgSO4 and concentrated to give desired product (203 mg, 34%). 1HNMR (CDCl3) (δ) 6.60 (s, 1H), 4.11 (s, 3H), 2.25 (s, 3H).
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