Visible-Light Induced Trifluoromethylation of Internal Olefinic C-H Bonds through Photoredox Catalysis

An approach for direct trifluoromethylation of internal olefins of α -oxoketene dithioacetals has been achieved by using Ru(bpy) 3 Cl 2 as photocatalyst and Togni’s reagent as trifluoromethylating agent under irradiation with visible light. Under a nitrogen atmosphere, a mixture of α -oxoketene dithioacetal (0.1 mmol), Togni’s reagent (0.15 mmol), Ru(bpy) 3 Cl 2 (0.005 mmol), and Na 2 CO 3 (0.3 mmol) in DMSO (1 mL) was stirred at room temperature for 72 h under 5 W Blue LEDS, which led to the trifluoromethylated products in 40% ～ 90% yield. This protocol provides an efficient and easy access to prepare trifluoromethylated dithioalkyl α -oxoketene acetals under mild conditions, and is highlighted by its operational simplicity and avoiding using toxic reagent. Furthermore, the gram-scale reaction of 1a suggested the potential application of this protocol in organic synthesis.