Visible-Light-Driven C–S Bond Formation Based on Electron Donor–Acceptor Excitation and Hydrogen Atom Transfer Combined System

Abstract

Developed herein is a visible-light-driven synthesis of sulfides by an electron donor–acceptor/single electron transfer and hydrogen atom transfer combined system without transition metals and strong oxidants. This reaction proceeds through the excitation of an electron donor–acceptor complex between a thiolate and an aryl halide, followed by the hydrogen atom transfer from an alkane to the generated aryl radical.

Sustainable Thioetherification via Electron Donor–Acceptor Photoactivation Using Thianthrenium Salts

“…Given previous reports, [3a–b] especially the thioetherification described by Bunnett et al., [13a] and the mechanistic findings described herein, a plausible mechanism for this C(sp 2 )−S coupling is proposed in Figure 2E. The proposed mechanism involves the formation of an intermediate EDA complex that induces a unimolecular nucleophilic substitution (S RN 1) radical chain.…”

“…On the other hand, an examination of various inorganic and organic bases revealed that carbonates and potassium phosphate tribasic prove to be suitable bases for this thioetherification reaction. The less expensive K 2 CO 3 ($ 0.08/gram) gave better results than Cs 2 CO 3 ($ 3.78/gram), which had been used in other reported EDA complex thioetherifications [3a–b] . Notably, an open‐to‐air experiment afforded identical results to those found under inert atmosphere, indicating that oxygen did not affect the transformation (entry 9).…”

“…As shown in Scheme 3, aldehyde ( 3 u , v ), amide ( 3 w , 3 x , 3 aa ), strained cyclopropyl ( 3 x ), ester ( 3 x , 3 y , 3 aa ), and ether ( 3 u, v , 3 aa , 3 ad – ae ) groups were efficiently incorporated. Although C‐halogen bonds are known to be reduced in various EDA complex transformations to generate aryl radicals, [3a,b, 13a] halogen substituents survived under the developed reaction conditions to afford brominated sulfides 3 ab – ae and iodinated sulfide 3 af in good yields. Retention of the halide handles in this protocol complements other reported thioether syntheses that proceed via reduction of the C−halogen bond, [3a,b] and allows further diversification of the sulfide structure by known procedures, such as metallaphotoredox catalysis [20]…”

“…reported different visible‐light‐assisted EDA complex methods to forge C(sp 3 )−S bonds readily. Akiyama and co‐workers designed a combined EDA complex and hydrogen atom transfer (HAT) system, [3b] while Song and co‐workers used various alkyl N ‐hydroxyphthalimide esters as electron‐acceptors [3c] . However, these reactions are air sensitive and/or proceed through C(sp 2 )−X reduction.…”

Correction: A photoexcited halogen-bonded EDA complex of the thiophenolate anion with iodobenzene for C(sp3)–H activation and thiolation

“…Upon publication of the original article, the authors became aware of another work in this area that reported a related transformation, given below as ref. 1 .…”