Abstract

4-(2-fluorophenyl)-7-methoxycoumarin (6) was synthesized by Pechmann reaction under mild conditions via a three step-reaction. The solution-state ¹H NMR spectra of 6 showed a strong intramolecular interaction between F and H5 (J_FH = 2.6 Hz) and ¹³C NMR suggested that this C-F^…H-C coupling is a through-space interaction. The 2‑D HOESY spectrum and ¹H‑{¹⁹F} 1‑D spectrum were also done to confirm this F^…H interaction. The single crystal X-ray structure and the DFT-optimized structure showed that the fluorinated phenyl ring favours the orientation with the fluorine atom is closer to H5 than H3. The X-ray structure also showed the existence of the intermolecular C-F^…H-C interactions.

Keywords: Fluorinated phenylcoumarin; Pechmann reaction; F^…H hydrogen bond; Through-space coupling; DFT

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Mzozoyana, V.; van Heerden, F. R.; Grimmer, C. Beilstein Arch. 2019, 2019124. doi:10.3762/bxiv.2019.124.v1

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