Photochemical aerobic oxidation of sulfides to sulfoxides: the crucial role of wavelength irradiation

Abstract

The sulfoxide moiety is recognized as one of the most important groups in organic and medicinal chemistry. Many efforts worldwide focus on developing novel and sustainable protocols, accessing sulfoxide-containing molecules. Photochemistry plays a unique role in sulfoxide synthesis, since this new emerging field, employing light as the energy source, is essential in developing novel and eco-friendly protocols. Herein, we report a novel, sustainable, light-driven protocol, where the impact of wavelength irradiation on sulfide aerobic photooxidation was examined. In this work, two different low-catalyst loading (0.05–0.5 mol%) protocols, utilizing anthraquinone as the photocatalyst (under CFL lamps or 427 nm irradiation) were developed and a catalyst-free protocol (under 370 nm irradiation) was also assessed. In addition, a broad scope of substrates was tested and extensive mechanistic studies were performed, in order to distinguish the mechanistic pathways that are followed in the different cases of aryl or alkyl sulfide oxidation under different wavelength irradiation. We also implemented our protocols towards the oxidation of several intermediates en route to Sulforaphane.