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

Abstract

Photoexcited acetophenone can catalyze the fluorination of unactivated C(sp3)–H groups. While acetophenone, a colorless oil, only has a trace amount of absorption in the visible light region, its photoexcitation can be achieved by irradiation with light generated by a household compact fluorescent lamp (CFL). This operational simple method provides improved substrate scope for the direct incorporation of a fluorine atom into simple organic molecules. CFL-irradiation can also be used to promote certain classic UV-promoted photoreactions of colorless monoarylketones and enones/enals.

Outer-Sphere Electrophilic Fluorination of Organometallic Complexes

“…Single-crystal X-ray diffraction studies showed the molecular structure of [3][BF 4 ] (Figure 1) to contain a metallocyclic ring system similar to that seen in 2, but with the formation of a new C−F bond at C (11). The Ru−C(6) bond in [3] compared to 2.046(2) Å), consistent with an increase in double bond character upon fluorination.…”

Visible‐Light Photocatalysis as an Enabling Tool for the Functionalization of Unactivated C(sp3)‐Substrates

“…The groups of Tan [92] and Chen [93] reported photocatalytic fluorination of unactivated C-H bonds by use of Selectfluor® as a fluorine source and anthraquinone (60) or acetophenone (61), respectively, as photocatalyst (Scheme 39). Despite their structural similarity, the ketone catalysts were suggested to perform different roles in the two studies.…”

A highly reducing metal-free photoredox catalyst: design and application in radical dehalogenations

“…After 24 h of irradiation time in the presence of PTH, benzyl 4-chlorobenzoate was successfully reduced, with the desired product being isolated in 83% yield. A variety of other activated aryl chlorides were subsequently examined with methyl benzoate, benzonitrile, and benzoic acid derivatives undergoing dechlorination in good yields (20)(21)(22).With a broad substrate scope and the potential of this metalfree photoredox system established, the physical aspects of PTH were studied in more detail, in particular the high excited state reduction potential, given by:where E 1/2 * is the excited state reduction potential, E ox 1/2 is the ground state oxidation potential, h is Planck's constant, c is the speed of light and l max is the photoluminescence maximum. 24 While the ground state oxidation potential of PTH (E ox 1/2 = 0.68 vs. SCE) 19 is only slightly lower than that of Ir(ppy) 3 (E ox 1/2 = 0.77 V vs. SCE), the photoluminescence maximum of PTH (l max = 445 nm, Fig.…”

“…After 24 h of irradiation time in the presence of PTH, benzyl 4-chlorobenzoate was successfully reduced, with the desired product being isolated in 83% yield. A variety of other activated aryl chlorides were subsequently examined with methyl benzoate, benzonitrile, and benzoic acid derivatives undergoing dechlorination in good yields (20)(21)(22).…”