Through-space ¹⁹F–¹⁵N couplings revealed the configuration of flubenzimine, with the CF₃ group on N4 pointing towards the lone pair of N5. The ¹⁹F–¹⁵N coupling constants were measured at natural abundance using a spin-state selective indirect-detection pulse sequence. As ¹⁵N-labelled proteins are routinely synthesized for NMR studies, through-space ¹⁹F–¹⁵N couplings have the potential to probe the stereochemistry of these proteins by ¹⁹F labelling of some amino acids or can reveal the site of docking of fluorine-containing drugs. Copyright © 2016 John Wiley & Sons, Ltd.

In the process of studying the chemistry of perfluoro[2.2]paracyclophanes (PFPCs), a novel class of compounds, it became necessary to identify some disubstituted products. To achieve this goal, we characterize in this work some monosubstituted PFPCs, identifying their ¹⁹F¹⁹F coupling patterns, and establishing a methodology for the assignment of their ¹⁹F chemical shifts. The pattern of coupling constants indicates a skewed geometry in which the upper deck moves towards or away from the substituent, depending on the substituent electron-donor character and size. Quantum chemical calculations, performed at the HF/6-311 + G(d,p)//B3LYP/EPR-III level of theory, confirmed the conformations inferred from coupling constants and reproduced well the values of the couplings. Transmission mechanisms for the FC term of four- and five-bond ¹⁹F¹⁹F couplings are discussed in detail. Understanding the conformational preferences of PFPCs and how they are reflected by the coupling constants facilitates the assignment of ¹⁹F chemical shifts in monosubstituted PFPCs and the identification of the disubstituted products. Copyright © 2011 John Wiley & Sons, Ltd.

Complete assignment of the ¹H and ¹⁹F chemical shifts in 4-fluoro-AF4 (1) were based on the nOes seen in its ¹⁹F-¹H HOESY spectrum. This allowed for identification of features which can further be applied to the assignment of the regiochemistry of substituted perfluoroparacyclophanes (PCPs) and AF4s: (i) an aromatic fluorine couples with the two fluorines in the closest bridge that are syn to it, with constants of ca. 20 Hz; (ii) an aromatic fluorine couples with the bridge fluorine five bonds away that is anti to it in the same paraphenylene moiety, with a constant of ca. 3.5 Hz; (iii) the geminal coupling of the bridge fluorines is 246 Hz if they have an ortho fluorine and 238 Hz if they do not; (iv) a bridge fluorine couples with those aromatic protons in the same paraphenylene moiety that are four or five bonds away and anti. These features have been used to assign the regiochemistry of the pseudo-ortho, pseudo-meta and pseudo-para-difluoro AF4s 2–4. It has also been demonstrated that SCS for the bridge fluorines can be used as well for this assignment. Copyright © 2009 John Wiley & Sons, Ltd.