Synthesis of fluorinated isoxazoles using Selectfluor™: preparation and characterization of 4-fluoroisoxazole, 4,4,5-trifluoroisoxazoline and 4,4-difluoro-5-hydroxyisoxazoline systems from one-pot and multi-step processes

3,5-Disubstituted 4-fluoroisoxazole, 4,4,5-trifluoroisoxazoline and 4,4-difluoro-5-hydroxyisoxazoline products were obtained from reaction of the corresponding isoxazoles with Selectfluor™ depending upon the reaction conditions. Although the fluorinations proceeded using conventional heating, microwave (μW) irradiation considerably shortened reaction times and enabled a high yielding one-pot cascade fluorination-cyclization from simple diketone substrates. In addition, a related 4-fluoroisoxazole-3-carboxyamide derivative was synthesized. [Display omitted]