反应详情

Glacial acetic acid and HBr (>40%) each 20 ml are successively added to methoxy benzopyran-4-one 2.9 g (0.0163 mol), stirred and refluxed for 1 h, and then the reactant liquor is modulated pH for 10-11 by KOH, the water layer is modulated pH for 2-3 by concentrated hydrochloric acid, and then extracted by ethyl acetate; the organic layers are combined and dried over anhydrous Na2SO4, cooled to precipitate black solid, and recrystallized by ethyl acetate, to obtain bright yellow crystal 2.17 g, m.p.: 142-144° C., yield: 81.2%.

1. temperaturerefluxed for 1 h
2. extractionextracted by ethyl acetate
3. dry with materialdried over anhydrous Na2SO4
4. temperaturecooled
5. customto precipitate black solid
6. customrecrystallized by ethyl acetate