A reinvestigation of the reactions of 3-substituted chromones with hydroxylamine. Unexpected synthesis of 3-amino-4H-chromeno[3,4-d]isoxazol-4-one and 3-(diaminomethylene)chroman-2,4-dione

Reactions of 3-substituted chromones (3-formylchromone, 3-formylchromone-3-oxime, and 3-cyanochromone) with hydroxylamine in alkaline medium were reinvestigated, and a proof of structures and a probable reaction pathway are presented. Syntheses of 2-aminochromone-3-carboxamide, 3-amino-4H-chromeno[3,4-d]isoxazol-4-one, and 3-(diaminomethylene)chroman-2,4-dione were developed.