Cu and Hydroquinone for the Trifluoromethylation of Unprotected Phenols.

Fluorination and trifluoromethylation are indispensable tools in the preparation of modern pharmaceuticals and APIs. Herein we present a concept for the introduction of a trifluoromethyl group into unprotected phenols employing catalytic copper(I) iodide and hydroquinone, tBuOOH, and the Langlois' reagent. The method proceeds under mild conditions and exhibits an extended substrate scope compared to the biocatalytic trifluoromethylation using laccase from Agaricus bisporus. Various functional groups such as aldehydes, esters, ethers, ketones and nitriles were tolerated. The hydroquinone‐mediated trifluoromethylation reaction allowed accessing trifluoromethylated phenols, which are cumbersome to prepare via previously known chemical methods. Cu and HQ can do: The presence of catalytic Cu and sub‐stoichiometric amounts of hydroquinone enables the direct radical trifluoromethylation of phenols, which are difficult to trifluoromethylate with other chemical methods. Instead of the anticipated radical quenching effect of hydroquinone, it led to a highly increased reaction rate and improved overall selectivity of the trifluoromethylation process. [ABSTRACT FROM AUTHOR]