The highly electrophilic fluorosulfoxonium cation [Ph2S(O)F]+[B(C6F5)4)]- is shown to promote (n+2) annulation on Donor-Acceptor (D-A) strained cycles. This study highlights new reactions catalysed by highly electrophilic sulfoxonium cations and the...

The strongly oxidizing, powerful electrophilic fluorination reagent [FXe][OTf] is shown to effect direct oxidative monofluorination of sulfoxides. This one-step, chloride promoter-free methodology provides access to so far inaccessible, yet highly desirable strongly Lewis acidic fluorosulfoxonium cations from electron-deficient and/or sterically demanding sulfoxides that are shown to be practically unreactive towards the previously reported XeF2/NEt4Cl system. Experimental and density functional theory studies have been conducted to assess the Lewis acidities of the prepared sulfur(VI) cations. Preliminary results obtained with chiral sulfoxides provide early insights into the mechanism of these fluorination reactions.