Photoredox-Catalyst-Enabled para-Selective Trifluoromethylation of tert-Butyl Arylcarbamates.

The direct incorporation of a trifluoromethyl group on an aromatic ring using a radical pathway has been extensively investigated. However, the direct highly para-selective C-H trifluoromethylation of a class of arenes has not been achieved. In this study, we report a light-promoted 4,5-dichlorofluorescein (DCFS)-enabled para-selective C-H trifluoromethylation of arylcarbamates using Langlois reagent. The preliminary mechanistic study revealed that the activated organic photocatalyst coordinated with the arylcarbamate led to para-selective C-H trifluoromethylation. Ten-gram scale reaction performs well highlighting the synthetic importance of this new protocol.