Synthesis of a deep-cavity thiacalix[4]arene

• Published in: Tetrahedron letters 2003-10, Vol.44 (44), p.8093-8097
• Main Authors: Lhoták, Pavel, Šmejkal, Tomáš, Stibor, Ivan, Havlı́ček, Jaroslav, Tkadlecová, Marcela, Petřı́čková, Hana
• Format: Article
• Language: English
• Subjects: alkylation; conformational analysis; thiacalixarenes; X-ray crystallography
• ISSN: 0040-4039; 1873-3581
• DOI: 10.1016/j.tetlet.2003.09.048

A novel thiacalix[4]arene derivative bearing four phenyl groups on the upper rim was prepared by the direct condensation of biphenyl-4-ol with elemental sulphur. As revealed by X-ray diffraction analysis, this compound adopts the cone conformation in the solid state, thus creating a cavity with an extended π-aromatic system potentially applicable for solid-state inclusion of suitable molecules. Subsequent alkylation (RI/K 2CO 3/acetone, R=Me, Et, Pr) yielded tetraalkylated derivatives, which were studied for their conformational preferences using 1H NMR spectroscopy. While the Me or Et derivatives are conformationally mobile and exhibit thermodynamic equilibria of several conformers in solution (CDCl 3 or CD 2Cl 2), the corresponding propoxy derivative is infinitely stable at room temperature. A novel thiacalix[4]arene derivative possessing a deep aromatic cavity was prepared using the direct condensation of biphenyl-4-ol with elemental sulphur. The conformational preferences of this compound and simple alkyl derivatives thereof were studied using a combination of NMR and X-ray diffraction techniques.