To a solution of 89 g (330 mmol) O-(mesitylsulfonyl)acetohydroxamate (1) in dioxane is added with stirring 30 mL perchloric acid (70%) at 0 °C within 10 min, and then stirred for another 10 min. After adding about 20 mL of the acid, the reaction mixture becomes pasty. The crude reaction mixture is poured into ice water to give a white solid of O-(mesitylsulfonyl)hydroxylamine, which is collected, washed with cold water (500 mL), then with cold petroleum ether (300 mL), and dried by maintaining suction for about 1 h; yield 55-65 g (77-92%).
The product should be stored in a refrigerator below 0 °C. Iodometric titration indicates that O-Mesitylenesulfonylhydroxylamine, thus prepared, contains 20-30% water. It can be used for most applications. Further purification can be achieved by the dissolution of a small amount of diethyl ether at room temperature and precipitation with petroleum ether.
