Catalytic Synthesis of 5-Fluoro-2-oxazolines: Using BF 3 ·Et 2 O as the Fluorine Source and Activating Reagent.

Hypervalent iodine catalyst-catalyzed nucleophilic fluorination of unsaturated amides using BF 3 ·Et 2 O as the fluorine source and activating reagent was reported. Various 5-fluoro-2-oxazoline derivatives were synthesized in good to excellent yields (up to 95% isolated yield) within 10 min. The process was efficient and metal-free under mild conditions. A mechanism involving a fluorination/1,2-aryl migration/cyclization cascade was proposed on the basis of previous work and experimental results.