Selective, Electrophilic Fluorinations Using N-Fluoro-o-benzenedisulfonimide

Article abstract of DOI:10.1021/jo00120a014

The synthesis of N-fluoro-o-benzenedisulfonimide (NFOBS, 2) and its use as an "electrophilic" fluorinating reagent with nucleophilic substrates is described and compared with that of N-fluorobenzenesulfonimide (NFSi, 3).NFOBS (2) is prepared in three steps in 81percent overall yield from commercially available o-benzenedisulfonic acid (4) and involves treatment of o-benzenedisulfonimide (6) with dilute fluorine (10percent F2/N2).Reaction of 2 with metal enolates, silyl enol ethers, and 1,3-dicarbonyl compounds affords the corresponding α-fluoro compounds in yields up to 95percent, with good control of mono- and difluorination.Fluorination of ortho-metalated aromatic compounds was achieved in modest to good yields (10-80percent).While the reactivities of 2 and 3 are similar, better yields were observed with the former reagent in the fluorination of metal enolates, Grignard and lithium reagents, while 3 gave better results with the ortho-lithiated aromatic substrates.The available evidence suggests an S_N2-type mechanism for the fluorination of nucleophilic substrates by these reagents.