Evidence for Ionic Intermediates in Fluorination of Alkenes with N–F Type of Reagents

Abstract 2-Exo-acetamido-7-syn-fluoro norbornane and 2-exo-acetamido-7-anti-fluoro norbornane were formed in the room temperature reaction of bicyclo[2.2.1]heptene in acetonitrile with N–F type reagents [1-chloromethyl-4-fluoro-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (F–TEDA), 1-fluoro-4-hydroxy-1,4-diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate) (NFTh) and 2,6-dichloro-1-fluoropyridinium triphlate (FPD–T)]. Such Meerwein-Wagner rearrangement and hydride shift indicated the formation of fluoro carbonium ions.