Preparation of 3-hydroxy-2,3-dialkoxy-2-phenylchroman-4-ones and 3,3-dihydroxy-2-alkoxy-2-phenylchroman-4-ones by oxidation of 3-hydroxyflavone with Copper(II) Bromide: Structure, reactivity and characterization

•Synthesis of chroman-4-one hemiacetals and hydrates.•Hemiacetals and hydrates were structurally characterized by SCXRD.•Hemiacetals are converted to hydrates with heat in non-alcoholic solvents.•Hemiacetals are kinetically preferred; hydrates are thermodynamically preferred.•Chromane-3,4-dione intermediate trapped as a quinoxaline.