Search

Abstract: Fluorine chemistry has taken a pivotal role in chemical reaction discovery, drug development, and chemical biology. NMR spectroscopy, arguably the most important technique for the characterization of fluorinated compounds, is rife with highly inconsistent referencing of fluorine NMR chemical shifts, producing deviations larger than 1 ppm. Herein, we provide unprecedented evidence that both spectrometer design and the current unified scale system underpinning the calibration of heteronuclear NMR spectra have unintentionally led to widespread variation in the standardization of 19F NMR spectral data. We demonstrate that internal referencing provides the most robust, practical, and reproducible method whereby chemical shifts can be consistently measured and confirmed between institutions to less than 30 ppb deviation. Finally, we provide a comprehensive table of appropriately calibrated chemical shifts of reference compounds that will serve to calibrate 19F spectra correctly. [ABSTRACT FROM AUTHOR]

Hydrofluoroethers are shown to alkylate tertiary amines readily under solvent-free conditions, affording valuable tetraalkylammonium perfluoroalkoxides bearing α-fluorines. The reaction of RFCF2OCH3 (RF=CF2CF3, CF2CF2CF3, and CF(CF3)2) with NR1R2R3 produces twenty new α-perfluoroalkoxides, [(CH3)NR1R2R3][RFCF2O] under mild conditions. These α-perfluoroalkoxides are easy to handle, thermally stable, and can be used for the perfluoroalkoxylation of benzyl bromides. [ABSTRACT FROM AUTHOR]

Replacement of the iodine atom in an iodine (III) CF3‐transfer reagent with a Te‐aryl moiety was accomplished in a three‐step synthetic sequence. Three compounds of this type have been prepared, two of which were characterized by X‐ray diffraction. Single crystal structures were also obtained for three related Te(IV) compounds unreported so far (4a, 4b, 6b). Comparison with the iodine (III) analogues indicate a large degree of structural similarity, however these species display an interesting decomposition pathway under thermal conditions. In addition to the expected Te−CF3 bond cleavage, C−F bond cleavage is also observed, unlike in the case of iodine (III) compounds. [ABSTRACT FROM AUTHOR]