Continuous Flow α-Trifluoromethylation of Ketones by Metal-Free Visible Light Photoredox Catalysis

A continuous-flow, two-step procedure for the preparation of alpha-CF3-substituted carbonyl compounds has been developed. The carbonyl substrates were converted in situ into the corresponding silyl enol ethers, mixed with the CF3 radical source, and then irradiated with visible light using a flow reactor based on transparent tubing and a household compact fluorescent lamp. The continuous protocol uses Eosin Y as an inexpensive photoredox catalyst and requires only 20 min to complete the two reaction steps.