Rhenium-Catalyzed Trifluoromethylation of Arenes and Heteroarenes by Hypervalent Iodine Reagents

Methyltrioxorhenium acts as a catalyst (5–10 mol %) for the direct electrophilic trifluoromethylation of various aromatic and heteroaromatic compounds using the hypervalent iodine reagent 1-(trifluoromethyl)-1,2-benziodoxol-3(1H)-one (1). The products are formed in up to 77% yield. Mixtures of regioisomers are obtained in the case of substituted and heteroaromatic substrates. The reaction, typically carried out in chloroform solvent at 70 °C, shows a significant induction period. Monitoring by EPR shows the involvement of radical species. A small kinetic deuterium isotope effect of 1.3 is observed for benzene.