N-fluorobenzenesulfonimide [(PhSO2)2NF] - A neutral N-F-containing electrophilic fluorinating agent

Abstract

The use of imidazolidinone 1 as the asymmetric catalyst has been found to mediate the fluorination of aldehyde substrates with N-fluorobenzenesulfonimide serving as the electrophilic source of fluorine. A wide range of functional groups, including olefins, esters, amines, carbamates, and aryl rings, can be readily tolerated on the aldehydic substrate.9 Various N-alkylimines derived from acetophenones were successfully monofluorinated using N-fluorosulfonimide (NFSI) in a mixture of acetonitrile and DMF at 0°C Alternatively the same procedure without DMF gave rise to diflourinated imines when performed at room temperature. The obtained α- and α,α-difluorinated imines were subsequently reduced to give the corresponding β-fluoro- and β,β-difluoroamines in good yield.10 NFSI was used for synthesis of novel 3,5-difluoropyridine-4- carboxaldehyde. Difluorination was achieved through the reaction of 3,5-dibromo-1,3-dioxolane pyridine with n-butyllithium followed by N-fluorobenzenesulfonimide at -120°C in good yield.11 Reaction of the in situ generated purine C-8 carbanion of a protected 5′- noraristeromycin derivative with N-fluorobenzenesulfonimide gave 8-phenylsulfonyl-5′-noraristeromycin rather than the expected 8-fluoro derivative. A single electron transfer (SET) mechanism is proposed for this occurrence. The phenylsulfonyl product offers a structural feature common to some anti-HIV agents.12 α-Fluorosulfonamides were prepared by electrophilic fluorination of tertiary sulfonamides using N- fluorobenzenesulfonimide as fluorinating agent and utilizing the dimethoxybenzyl group (DMB) as a new sulfonamide protecting group. Removal of the DMB group with TFA/CH2Cl2 gave primary and secondary α-fluorosulfonamides.13 D. Y. Kim and coworkers reported the catalytic enantioselective fluorination of β-keto phosphonates catalyzed by a chiral palladium complex. Treatment of β-keto phosphonates with N-fluorobenzenesulfonimide (NFSI) as electrophilic fluorinating reagent under mild reaction conditions afforded the corresponding α-fluorinated β-keto phosphonates in moderate to excellent yields with excellent enantiomeric excesses.14. © Georg Thieme Verlag Stuttgart.