Relative Electrophilic Fluorinating Power as Assayed by Competitive Catalytic Halogenation Reactions

Catalytic fluorination/chlorination competition experiments of β ‐keto ester 5 were used to assess the relative fluorinating activity of various electrophilic NF reagents (containing an NF bond). Thus, in the halogenation reactions catalyzed by the [Ti(TADDOLato)] complex 1 (=bis(acetonitrile)dichloro[(4 R ,5 R )‐2,2‐dimethyl‐ α , α , α ′, α ′‐tetra(naphthalen‐1‐yl)‐1,3‐dioxolane‐4,5‐dimethanolato(2−)‐ κO , κO ′]titanium), the activity range of a series of commercially available reagents spans more than two orders of magnitude. Selectfluor TM (=1‐(chloromethyl)‐4‐fluoro‐1,4‐diazoniabicyclo[2.2.2]octane bis(tetrafluoroborate); 9 ; also called F‐TEDA; TEDA=triethylenediamine) reacts more than 100 times faster than 1‐fluoropyridinium tetrafluoroborate.