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Updated: Jul 11, 2025

Protocol for the Synthesis of Ortho-trifluoromethoxylated Aniline Derivatives
Published on: January 19, 2016
Synthesis and characterization of trifluoromethylcarboxonium salts
Thomas Saal1, Ralf Haiges1, Karl O Christe1
1Loker Hydrocarbon Research Institute and Department of Chemistry, University of Southern California, Los Angeles, CA 90089-1661, USA. kchriste@usc.edu.
Abstract:
The low-temperature protonation of trifluoroacetic acid with the superacids HF/SbF5 and HF/AsF5 resulted in the syntheses of the first examples of trifluoromethylcarboxonium salts. The less acidic trifluoromethylacetamide was also protonated in the same fashion, resulting in exclusive protonation of the carbonyl function. Their [SbF6]- and [AsF6]- salts were characterized by crystal structures, vibrational and multinuclear NMR spectra, and by electronic structure calculations. These salts are thermally unstable, colorless solids, stabilized by very strong hydrogen bonding. The proton NMR resonances of the [CF3C(OH)2]+[SbF6]- and [CF3C(OH)2]+[AsF6]- salts occur at an unprecedented 16.0 and 15.7 ppm, respectively, thus extending the upper limit of the range of observed proton NMR chemical shifts from 14 to 16 ppm.
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