Direct Synthesis of 4‑Fluoroisoxazoles through Gold-Catalyzed Cascade Cyclization–Fluorination of 2‑Alkynone O‑Methyl Oximes

A tandem protocol for the synthesis of fluorinated isoxazoles has been developed via catalytic intramolecular cyclizations of 2-alkynone O-methyl oximes and ensuing fluorination. The reactions proceed smoothly at room temperature in the presence of 5 mol % of (IPr)­AuCl, 5 mol % of AgOTs, 2.5 equiv of Selectfluor, and 2 equiv of NaHCO₃. This process features an efficient one-pot cascade route to fluoroisoxazoles with high yields and high selectivity under mild reaction conditions.