Synthesis of 3,4,5-trisubstituted isoxazoles through gold-catalyzed cascade cyclization-oxidative alkynylation and cyclization-fluorination of 2-alkynone O-methyloximes

Gold-catalyzed tandem cyclization-oxidative alkynylation and cyclization-fluorination reactions of 2-alkynone O-methyloximes are described. The reactions proceed smoothly at room temperature in the presence of 10 mol % of (PPh₃)AuNTf₂, 2.5 equivalents of selectfluor, and 2 equivalents of K₃PO₄. 2-Alkynone O-methyloximes undergo intramolecular oxyauration/cyclization and ensuing oxidative cross-coupling and fluorination process to afford the corresponding 3,4,5-trisubstituted isoxazoles in a cascade manner.