Synthesis of [1] benzopyrano [3, 4-d] isoxazol-4-ones from 2-substituted chromone-3-carboxylic esters. A reinvestigation of the reaction of 3-acyl-4-hydroxycoumarins …
Chemical evidence is presented in support of their structures. The lla: 12a ratio can be affected by varying the reaction conditions. By using a 1/1.2/2 molar ratio of 3-acyl- 4hydroxycoumarins (9), hydroxylamine hydrochloride, and potassium acetate, respectively, a series of compounds 11 was obtained in good yields.