2-Polyfluoroalkylchromones. 10. Synthesis of regioisomeric 3-(2-hydroxyaryl)-5-polyfluoroalkyl- and 5-(2-hydroxyaryl)-3-polyfluoroalkylisoxazoles and determination of their structures by 1H, 19F, and 13C NMR spectroscopy

The reactions of 2-hydroxy-2-polyfluoroalkylchroman-4-ones with hydroxylamine yield, through Δ2-isoxazolines as intermediate products, 3-(2-hydroxyaryl)-5-polyfluoroalkylisoxazoles. Analogous reactions with 2-polyfluoroalkylchromones afford β-diketone monooximes, which in an acidic medium undergo cyclodehydration into 5-(2-hydroxyaryl)-3-polyfluoroalkylisoxazoles. The structures of regioisomeric 3- and 5-polyfluoroalkylisoxazoles were determined using 1H, 19F, and 13C NMR spectroscopy.