Hypervalent iodine reagents, direct trifluoromethylation

Niedermann KM (2012) Direct trifluoromethylation of organonitrogen compounds with hypervalent iodine reagents. Dissertation ETH no. 20465, ETH Zurich. doi 10.3929/ethz-a-007567196... 

Niedermann K, Friih N, Senn R, Czamiecki B, Verel R, Togni A (2012) Direct electrophilic N-trifluoromethylation of azoles by a hypervalent iodine reagent. Angew Chem Int Ed 51 6511-6515. doi 10.1002/anie.201201572... 

A novel methyltrioxorhenium (MTO) catalyzed methodology for the direct trifluoromethylation of both activated and nonactivated arenes and heteroarenes using an easily accessible, shelf-stable hypervalent iodine trifluoromethylating reagent has been developed by Togni and coworkers (Scheme 9.21). This reagent system exhibited a broad substrate scope in direct aromatic trifluoromethylation. 

Stuart and co-workers have reported on a novel, stable fluorinating reagent based on a cyclic hypervalent iodine(m) skeleton typically used for trifluoromethylation. Model studies for the reagent focused on the fluorination of ethyl-3-oxo-3-phenylpropanoate and showed that addition of TREAT-HF (triethylamine trihydrofluoride) is essential for the reaction to proceed. Judicious control of stoichiometry, concentration, and temperature allowed good yields of the monofluorinated compound to be obtained (Scheme 15.37). No fluorination was observed in the absence of the fluor-oindane. A range of p-ketoesters and 1,3-diketones were evaluated under the optimal conditions, and it was shown that the relative reactivity could be directly correlated with the substrate s enol content, as observed previously... 

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