A mild and fast photocatalytic trifluoromethylation of thiols in batch and continuous-flow

Abstract

S–CF₃ bonds are important structural motifs in various pharmaceutical and agrochemical compounds. However, their preparation remains a major challenge in synthetic organic chemistry. Here, we report the development of a mild and fast photocatalytic trifluoromethylation of thiols. The combination of commercially available Ru(bpy)₃Cl₂, visible light and inexpensive CF₃I gas proved to be an efficient method for the direct trifluoromethylation of thiols. The protocol is demonstrated on a wide range of aromatic, hetero-aromatic and aliphatic substrates in both batch and continuous microflow (32 examples, 52–98% yield). Process intensification through continuous microflow application resulted in a 15-fold increase in production rate (0.25 mmol min⁻¹) due to improved gas–liquid mass transfer, enhanced irradiation as well as convenient handling of the gaseous CF₃ source. Furthermore, the efficiency of the flow process allowed to reduce the amount of CF₃I (1.1 equivalent) to reach full conversion.