Electron and hydrogen atom donor photocatalysts in situ generated from benzimidazolium salts and hydride reagents

• Published in: Journal of photochemistry and photobiology 2023-08, Vol.16, p.100195, Article 100195
• Main Authors: Miyajima, Ryo, Kiuchi, Takehiro, Ooe, Yuki, Iwamoto, Hajime, Takizawa, Shin-ya, Hasegawa, Eietsu
• Format: Article
• Language: English
• Subjects: Benzimidazoline and benzimidazolium couple; Electron and hydrogen atom donor; Hydride donor reagent; Reducing photocatalyst; Reductive desulfonylation
• ISSN: 2666-4690; 2666-4690
• DOI: 10.1016/j.jpap.2023.100195

•A photocatalytic system composed of benzimidazoliums and hydride donor reagents.•In situ generation of benzimidazolines as photocatalytic species.•Photo-excitation of polycyclic aryl, triarylamine, or phenyl-sulfate substituted benzimidazolines.•Electron as well as hydrogen atom donor (eh-donor) photocatalysts.•Reductive desulfonylation reactions involving N–S or C–S bond cleavage. Photocatalytic systems consisting of 2-substituted benzimidazoliums (BI+–R, R = polycyclic aryl, triarylamine or phenyl-sulfate) and stoichiometric hydride donor reagents were developed. Light emitting diode irradiation of these photocatalysts in the presence of NaBH4 or picoline borane promotes desulfonylation reactions of an N-sulfonyl indole, N-sulfonyl amide and α-sulfonyl ketone. Absorption spectroscopic and redox potential measurements as well as density functional theory calculations were carried out to gain mechanistic information. Benzimidazolines (BIH–R), generated in situ by hydride reduction of BI+–R, serve as both an electron and hydrogen atom donor photocatalysts in these reductive desulfonylation reactions, which contrasts to ordinary reducing photocatalysts that simply donate electrons. [Display omitted]