Elemental fluorine. Part 10.1 Selective fluorination of pyridine, quinoline and quinoxaline derivatives with fluorine–iodine mixtures

Abstract

Selective fluorination of a range of pyridine and quinoline substrates to give corresponding 2-fluoro-derivatives can be readily achieved in high yield at room temperature using elemental fluorine–iodine mixtures. Reaction of fluorine with iodine forms, in situ, systems that function like sources of both iodonium and fluoride ions and fluorination of heterocyclic derivatives is suggested to proceed by fluoride ion attack on intermediate N-iodo-heterocyclic species. Quinoxaline derivatives react under similar conditions to give either the 2-fluoro- or 2,3-difluoro-quinoxaline derivatives depending on the ratio of fluorine passed through the solution. In related processes, pyridine can be alkoxylated upon reaction of an appropriate alcohol and fluorine.