A cooperative allylic fluorination: combination of nucleophilic and electrophilic fluorine sources

Visible light-promoted metal-free sp3-C–H fluorination

“…4–13 For example, the Sanford, 4 Yu, 5 and Doyle 6 groups have each reported an efficient palladium catalyst system while the Groves 7 and the Lectka 8 groups have disclosed a manganese and a copper catalyst system, respectively. The Inoue, 9 Tang, 10 and Hartwig 11 groups have also shown that N -oxyl radical and silver salts can catalyze or promote C–H fluorination.…”

“…The Inoue, 9 Tang, 10 and Hartwig 11 groups have also shown that N -oxyl radical and silver salts can catalyze or promote C–H fluorination. More recently, photolytic activation methods have also been reported by Britton, 12 Lectka, 8c and Tan 13 using decatungstate, 1,2,4,5-tetracyanobenzene (TCB), and anthraquinone (AQN) as the catalyst, respectively.…”

“…8c,13 To test this hypothesis and to further exclude the possibility that Selectfluor reacted with acetophenone to form a transient reactive species not detectable by UV, we examined if CFL-irradiation could also promote unimolecular C–H abstraction of monoarylketones. Indeed, CFL-irradiation induced the Norrish type II cleavage and Norrish–Yang cyclization of valerophenone ( 22 ) ( n →π* transition λ max ~325 nm) to give 23 – 26 (Fig.…”

“…21 The unimolecular photoreaction of 22 further suggest that acetophenone can function as a C–H abstraction catalyst instead of a photosensitizer in activating Selectfluor toward C–H abstraction. 8d,13 …”

Site selectivities in fluorination

“…Lectka's group also reported allylic C-H fluorinations with excellent site selectivities [34] . A mixture of silver and selenium salts in the presence of NfPyBF4 enabled fluorination of alkenes 34 to produce various allylic fluorides 35.…”