Metal‐Free Visible‐light Mediated C−S Bond Formation

The upsurge in interest in the development of methodologies for the synthesis of sulfur‐containing compounds via the use of visible‐light has been established as a sustainable tool in organic chemistry. Particularly, visible‐light mediated C−S bond formation has gained popularity due to its operational simplicity, minimized by‐products, easy handling, mild reaction conditions, etc. Photochemistry not only provides a sustainable way to synthesize complex molecules but also has the ability to overcome many challenges which are difficult to attain by conventional thermal pathways. Owing to the biological importance of sulfur‐containing compounds, the present review focused on the C−S bond formation under metal‐free conditions mediated by visible‐light. The objective of the current review is to bring out the unearthing collection regarding C−S bond formation via photoredox catalysis. For better understanding, the review is categorized according to the mode of reactions viz, C−S bond formation via difunctionalization of alkenes and alkynes, C−S bond formation via C−H functionalization, and C−S bond formation via radical cyclization. All the reactions in each of the sections are described with selected examples with a proper explanation of the proposed mechanism. The review summarizes the visible‐light mediated C−S bond‐forming reactions under metal‐free conditions. In particular, it describes the C−S bond formations via difunctionalization strategy, C−H functionalization, and radical cyclization. Among various reactions presented, the EDA complex‐enabled reactions and sunlight‐mediated methodologies are interesting and underdeveloped.