Synthetic method of piroxicam drug intermediate 3-oxo-1,2-benzisothiazole-1,1-dioxo-2-ethyl acetate
A technology of benzisothiazole and piroxicam, applied in the direction of organic chemistry, can solve problems such as many adverse reactions in the gastrointestinal tract, and achieve the effects of reducing reaction temperature and reaction time, reducing intermediate links and improving reaction yield
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[0011] Example 1:
[0012] In a reaction vessel equipped with a stirrer, reflux condenser, dropping funnel, and thermometer, add 2.16mol of saccharine (2), 2.1L of nitromethane, control the stirring speed to 160rpm, and raise the solution temperature to 110°C, Slowly add 2.3 mol of ethyl acetate (3), continue to stir for 11 hours after the addition is complete, distill most of the nitromethane, pour the reactant into a 15% potassium chloride solution, and filter with suction to obtain a white solid. Recrystallization of 900ml with 80% acetonitrile mass fraction, lower the solution temperature to 3℃, let stand for 30h, suction filter, wash with 90% mass fraction toluene, dehydrated with anhydrous calcium sulfate to obtain 3-oxo-1,2-benzene 418.35 g of ethyl isothiazole-1,1-dioxo-2-ethyl acetate, with a yield of 72%.
Example Embodiment
[0013] Example 2:
[0014] In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, add 2.16mol of saccharine (2), 2.2L of nitromethane, control the stirring speed to 170rpm, and increase the solution temperature to 112℃, Slowly add ethyl acetate (3) 2.4mol, continue to stir after the addition for 112h, distill most of the nitromethane, pour the reactant into a 17% potassium chloride solution, and filter with suction to obtain a white solid. 900ml mass fraction of 82% acetonitrile recrystallization, lower the solution temperature to 4 ℃, stand for 32h, suction filtration, wash with 92% mass fraction of toluene, dehydrated activated alumina to obtain 3-oxo-1,2-benzo Isothiazole-1,1-dioxo-2-ethyl acetate is 435.78g, the yield is 75%.
Example Embodiment
[0015] Example 3:
[0016] In a reaction vessel equipped with a stirrer, a reflux condenser, a dropping funnel, and a thermometer, add 2.16mol of saccharine (2), 2.3L of nitromethane, control the stirring speed to 190rpm, and raise the solution temperature to 115°C. Slowly add ethyl acetate (3) 2.5mol, continue to stir for 13h after the addition is complete, distill out most of the nitromethane, pour the reactant into a 20% potassium chloride solution, and filter with suction to obtain a white solid. Recrystallize with 900ml mass fraction of 85% acetonitrile, lower the temperature of the solution to 5℃, stand for 36h, suction filter, wash with 95% mass fraction of toluene, dehydrated with anhydrous calcium sulfate to obtain 3-oxo-1,2-benzene 470.64 g of ethyl isothiazole-1,1-dioxo-2-ethyl acetate, with a yield of 81%.
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