jo301609g_si_010.cif (53.15 kB)

TEFDDOLs (α,α,α′,α′-Tetrakis(perfluoroaryl/alkyl)-2,2′-dimethyl-1,3-dioxolane-4,5-dimethanols): Highly Fluorinated Chiral H‑Bond Donors and Brønsted Acids with Distinct H‑Bonding Patterns and Supramolecular Architectures

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posted on 20.02.2016, 06:00 by Albrecht Berkessel, Sonja S. Vormittag, Nils E. Schlörer, Jörg-M. Neudörfl
The synthesis of six enantiopure α,α,α′,α′-tetrakis­(perfluoroalkyl/aryl)-2,2′-dimethyl-1,3-dioxolane-4,5-dimethanols (TEFDDOLs), by addition of perfluorinated organolithium reagents or Ruppert’s reagent (TMS-CF3) to isopropylidene tartaric dichloride, is reported. X-ray crystal structures of the TEFDDOLs alone or in complexes with H-bond acceptors such as water and DABCO revealed that this new class of highly fluorinated chiral 1,4-diols forms distinct intra- and intermolecular H-bond patterns. Intramolecular OH–OH bonding accounts for the relatively high acidity of the perfluoroalkyl TEFDDOLs (pKa in DMSO: tetrakis-CF3, 5.7; tetrakis-C2F5, 2.4). For the tetrakis­(perfluorophenyl) TEFDDOL, a quite unusual “pseudo-anti” conformation of the diol, with no intramolecular (and no intermolecular) OH–OH bonds, was found both in the crystal and in solution (DOSY and NOESY NMR). The latter conformation results from a total of four intramolecular OH–Faryl hydrogen bonds overriding OH–OH bonding. Due to their H-bonding properties, the TEFDDOLs are promising new building blocks for supramolecular and potentially catalytic applications.