Protocol for Visible-Light-Promoted Desulfonylation Reactions Utilizing Catalytic Benzimidazolium Aryloxide Betaines and Stoichiometric Hydride Donor Reagents
Eietsu Hasegawa, Tsukasa Tanaka, Norihiro Izumiya, Takehiro Kiuchi, Yuuki Ooe, Hajime Iwamoto, Shin‐ya Takizawa, Shigeru Murata
Abstract
An unprecedented photocatalytic system consisting of benzimidazolium aryloxide betaines (BI+–ArO–) and stoichiometric hydride reducing reagents was developed for carrying out desulfonylation reactions of N-sulfonyl-indoles, -amides, and -amines, and α-sulfonyl ketones. Measurements of absorption spectra and cyclic voltammograms as well as density functional theory (DFT) calculations were carried out to gain mechanistic information. In the catalytic system, visible-light-activated benzimidazoline aryloxides (BIH–ArO–), generated in situ by hydride reduction of the corresponding betaines BI+–ArO–, donate both an electron and a hydrogen atom to the substrates. A modified protocol was also developed so that a catalytic quantity of more easily prepared hydroxyaryl benzimidazolines (BIH–ArOH) is used along with a stoichiometric hydride donor to promote the photochemical desulfonylation reactions.