Monofluoromethyl derivatives of various nucleophiles have been synthesized using a new electrophilic monofluoromethylating reagent developed. The S-(monofluoromethyl)diarylsulfonium tetrafluoroborate has been shown to be effective for the introduction of an electrophilic monofluoromethyl group into C, S, O, N, and P nucleophiles. This methodology has been expanded for the synthesis of various biologically important compounds.