Metal-Free Photoredox Catalyzed Formation of S-C-S and C-S Bonds from Coupling of Diaryl Sulfide/Benzyl Chlorides with Dichloromethyl Derivatives

Abstract

A metal-free photoredox method for the synthesis of S-C-S and C-S bonds has been developed, offering a sustainable and efficient approach to produce diaryl dithioacetals and aryl benzyl sulfides. The method employs 4CzIPN as a photocatalyst and DIPEA as a base, enabling the formation of sulfur and carbon radicals through single electron transfer (SET) and halogen atom transfer (XAT) mechanisms. This protocol features a broad substrate scope, moderate to excellent yields, and scalability under solvent-free conditions or using water as a green solvent. Gram-scale synthesis and sunlight-driven reactions demonstrate its potential for industrial applications. Mechanistic studies, including fluorescence quenching and radical trapping experiments, have confirmed that DIPEA serves as a quencher of the excited state of 4CzIPN and that the reaction involves a radical pathway. This environmentally friendly strategy provides a versatile platform for constructing valuable sulfur-containing compounds with applications in synthetic chemistry and drug development.