Access to Sulfoxides under NHC/Photocatalysis via a Radical Pathway

Abstract

A photocatalyzed transformation from sulfinic acids to sulfoxides under visible-light irradiation in the presence of Nheterocyclic carbene is established. Various alkyl groups from four-substituted Hantzsch esters or Meyer nitriles are smoothly converted to the corresponding sulfoxides through a radical coupling pathway in the presence of 1,1-carbonyldiimidazole. This method allows sulfoxide synthesis to refrain from relying on the oxidation of sulfides and provides an alternative route for the preparation of sulfoxides.

Reductive Coupling of Sodium Sulfinates for the Synthesis of Thiosulfonates

“…Column chromatography was performed on silica gel (300-400 mesh). 1 H NMR, 13 C NMR and 19 F NMR spectra were recorded on a Bruker Avance-400 spectrometer in CDCl3 as solvents at room temperature. Chemical shifts are expressed in parts per million (ppm) and referenced to the residual solvent peak.…”

“…Organosulfur compounds are widely existed in natural products, agrochemicals, and pharmaceuticals, with sulfur being the fifth most used element in approved drugs following carbon, hydrogen, oxygen, and nitrogen. 1,2 Thiosulfonates are an important class of sulfur-containing compounds, which have shown broad biological properties such as antibacterial, antiviral, and antifungal activities. 3 Moreover, thiosulfonates have been increasingly used as synthetic intermediates in organic synthesis due to their better reactivity and stability compared with sulfenyl halides and disulfides.…”

Exploring the synthetic application of sulfinyl radicals

“…16B). 94 Very recently, Larionov's group used sulfinyl sulfones as reactive intermediates to provide a direct and metal-free strategy for the preparation of sulfoxides through decarboxylative sulfinylation (Fig. 16C).…”

N-Heterocyclic Carbene-Mediated Carbon–Sulfur Bond-Forming Reactions

“…The radical coupling pathway is also an efficient method to construct the C−S bond. Wu and colleagues 89 recently disclosed a novel method for the generation of simple sulfoxide 192 under visible light irradiation via an NHC/Ir cooperative catalytic process. Sulfinic acid 190 can be activated by 1,1-carbonyldiimidazole (CDI), and the afforded sulfinyl azolium intermediate 194 can be reduced by tetra-substituted Hantzsch ester 191 via a single-electron-transfer (SET) process to give sulfinyl radical intermediate 195 (Figure 33).…”