Thianthrenium-Enabled Phosphorylation of Aryl C–H Bonds via Electron Donor–Acceptor Complex Photoactivation

Abstract

An efficient strategy for the preparation of aryl phosphonates via blue-light-promoted single electron transfer process of an EDA complex between phosphites and thianthrenium salts has been demonstrated. The corresponding substituted aryl phosphonates were obtained in good to excellent yields, and the byproduct thianthrene can be recovered and reused in quantity. This developed method realizes the construction of aryl phosphonates through the indirect C–H functionalization of arenes, which has potential application value in drug discovery and development.

Visible-light-driven C(sp3)–H alkylation of heterobenzylic amines via electron donor–acceptor complexes

“…First, the control experiment showed that organophosphine, KOCH 3 and photoirradiation were indispensable for this reaction (entries 2–5). Replacing L with another tertiary amine electron donor, namely DIPEA, led to a significantly lower yield 11,25 (entry 6), which indicated that organophosphines were more suitable electron donors than were tertiary amines. Substitution of L with BINAP, DPEphos, Xantphos or triphenyl phosphorus, frequently used electron donors, resulted in dramatic decreases in yield (entries 7–10).…”

“…8 The classical EDA photochemical approaches are based on the intermediates involved in EDA complex formation with stoichiometric amounts of donor and acceptor, where both components end up in the product structure. 9 According to further research, the donor or acceptor can also act as a catalyst to promote the radical coupling between an electron-deficient or electron-rich substrate and another substrate, decoupling the complexation/photoactivation steps from the substrate functionalization 10,11 (Scheme 1A).…”

Synthetic Applications of Sulfonium Salts as Aryl Radical Precursors

“…The EDA complex 217 was generated between electron-poor biphenyl thianthrenium salt 216 and DMP, which attack by nucleophiles in the reaction mixture, resulting in the formation of the target product 221 (Scheme 31). [39] While the halogenation of arylthianthrenium salts has been achieved, the necessity for equivalent copper salts restricts the practical applicability of this approach. In 2023, Cornella, Ritter, and co-workers reported the nickel-catalyzed halogenation of arylthianthrenium salts.…”

“…Finally, 220 was subjected to nucleophilic attack by nucleophiles in the reaction mixture, resulting in the formation of the target product 221 (Scheme 31). [39] …”

Site-selective C–H difunctionalization of N-alkyl activated azaarenes via the synergistic catalysis of graphene oxide and visible light

“…3 Other researchers also found that the utilization of stoichiometric oxidants or bases could drive radicals to attack heteroarenium salts, which formed monoalkylation products under neutral conditions. 4 For the difunctionalization of N -heteroareniums (Scheme 1a, eqn (2)), the Yan group reported that Cu-catalyzed quinoliniums and benzothiazolims achieved the selective construction of C sp 2 −X bonds from halogen anions and nucleophilic carbon atoms via radical process. 5 All of the above nonclassical Minisci-type reactions involved radical-based processes via single-electron transformation using photoredox catalysis or oxidants.…”