Effect of cycloalkene structure on fluorination with 1-chloromethyl-4-fluoro-1,4-diazonia[2.2.2]octane bis(tetrafluoroborate) (F-TEDA)

Abstract

Liquid phase fluorination of norbornene with 1-chloromethyl-4-fluoro-1,4-diazonia[2.2.2]octane bis(tetrafluoroborate)—F-TEDA resulted in the formation of two rearranged Ritter type products: 2- exo-acetamido-7- syn-fluoro norbornane and 2- exo-acetamido-7- anti-fluoro norbornane in 1:1 ratio in acetonitrile, while the presence of an external nucleophile, e.g. water or methanol resulted in formation of two additional rearranged products: 2- exo-hydroxy or methoxy -7- syn-fluoro norbornane and 2- exo-hydroxy or methoxy-7- anti-fluoro norbornane. Fluorination of cycloalkenes obeys a simple second order rate equation, relative rates close to unity were found for norbornene/cyclohexene and cyclopentene/cyclohexene pairs. Activation parameters were determined for cycloalkenes in acetonitrile–water (Δ H ‡=14 kcal mol −1 and Δ S ‡=−20 cal mol −1K −1 for norbornene), while the Winstein–Grunwald solvent polarity variation had negligible effect.