¹⁹F-centred NMR analysis of mono-fluorinated compounds

Abstract

19F is the focal point of broadband, phase-sensitive 2D NMR experiments that provide 1H, 13C and 19F chemical shifts, values of JHF, JHH, and JFC coupling constants and 13C-induced 19F isotopic shifts to elucidate structures of fluorinated molecules.

Obtaining Pure 1H NMR Spectra of Individual Pyranose and Furanose Anomers of Reducing Deoxyfluorinated Sugars

“…58 During the course of our work, Uhri ́n and Bell published a set of 2D 1 H− 19 F experiments for mixture analysis, and while this was not emphasized, it also featured a demonstration on FDGlc-3. 59 Recently, the selective 1D FESTA (fluorine-edited selective TOCSY acquisition) experiment has been proposed for the analysis of mixtures of fluorinated compounds. 60−62 As illustrated The Journal of Organic Chemistry in Figure 1b, the experiment starts with the selective excitation of a chosen fluorine resonance.…”

“…This offers an exceptionally high probability of discrimination between different fluorinated components in the mixture and allows obtaining clean 1 H NMR subspectra for individual spin systems. FESTA compares to the 2D 19 F− 1 H CP-DIPSI3-DIPSI2 experiment, which is part of the aforementioned set of experiments by Uhri ́n and Bell, 59 in similar ways as does 1D sel-TOCSY to 2D TOCSY and can thus be seen as complementary. Just like sel-TOCSY, FESTA thus holds the advantage of short experimental times (from seconds to minutes depending on the amount of signal averaging needed) and, thanks to the selective 19 F excitation and polarization transfer with gradient pulses, should show fewer spectral complications from intense signals coming from other anomers compared to nonselective 2D methods (cf.…”

“…Although not demonstrated on fluorosugars, Krishnamurthy and co-workers published a similar 3D 19 F– 1 H heteronuclear TOCSY filtered experiment for mixture analysis, but this experiment requires very long experimental times (reported 60 h) . During the course of our work, Uhrín and Bell published a set of 2D 1 H– 19 F experiments for mixture analysis, and while this was not emphasized, it also featured a demonstration on FDGlc-3 …”

“… 58 During the course of our work, Uhrín and Bell published a set of 2D 1 H– 19 F experiments for mixture analysis, and while this was not emphasized, it also featured a demonstration on FDGlc-3. 59 …”

Pure shift FESTA: An ultra‐high resolution NMR tool for the analysis of complex fluorine‐containing spin systems

“…However, with only one 19 F per molecule, simple one-dimensional (1D) 19 F NMR provides limited structural information. Multidimensional methods utilising fluorine-proton ( 19 F-1 H) [12][13][14][15][16][17][18] or fluorine-carbon ( 19 F-13 C) correlations, 19,20 or both, [21][22][23][24] can be used to circumvent overlap in 1 H NMR spectra by dispersing signals over multiple dimensions. In particular, the two-dimensional (2D) GET-SERF experiment provides crucial conformational information through n J HF couplings to a specific 19 F atom whilst removing the effects of all other J HH and J HF .…”