Cl[C:2]([O:4][CH3:5])=[O:3].C(#N)C.[F:9][C:10]([F:22])([F:21])[C:11]1[C:12]([S:17]([NH2:20])(=[O:19])=[O:18])=[N:13][CH:14]=[CH:15][CH:16]=1>C(N(CC)CC)C>[F:21][C:10]([F:9])([F:22])[C:11]1[C:12]([S:17]([NH:20][C:2](=[O:3])[O:4][CH3:5])(=[O:19])=[O:18])=[N:13][CH:14]=[CH:15][CH:16]=1Methyl chloroformate (3.31 g, 35 mmol) was added under cooling with ice to a dry acetonitrile (150 ml) solution containing 3-trifluoromethylpyridine-2-sulfonamide (7.91 g, 35 mmol) and triethylamine (16 ml), and the mixture was continuously stirred at room temperature for 3 hours. Then, the solvent was distilled off under reduced pressure, and the residue was dissolved in 300 ml of water. A small amount of insoluble substances were removed by filtration, and the filtrate was adjusted to pH of 1 to 2 with concentrated hydrochloric acid under cooling with ice. Precipitated crystals were collected by filtration and thoroughly washed with water, then washed with a solvent mixture of ethyl ether/n-hexane and dried to obtain 4.4 g of desired methyl N-(3-trifluoromethylpyridine-2-sulfonyl)carbamate. Melting point: 128°-129° C.
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