Intramolecularly Bridged Calix[4]arenes with Pronounced Complexation Ability toward Neutral Compounds

Slavik, P.; Eigner, V.; Lhotak, P.
Org. Lett. 2015, 17, 2788-2791
 DOI:10.1021/acs.orglett.5b01200 

Abstract: Regioselective derivatization via an organomercury intermediate allowed for the introduction of carboxylic acid functionality into the meta position of the calix[4]arene skeleton. Intramolecular Friedel–Crafts cyclization led to a novel type of calixarene containing a ketone bridging moiety. Subsequent attack of the ketone by organometallic compounds occurred selectively from outside providing tertiary alcohols with the OH group oriented inside the cavity. These compounds can complex neutral molecules both in the solid state (X-ray) and in solution (NMR) using the cooperative effect of hydrogen bonding (OH) and CH−π interactions from within the cavity.

Shaping of Calix[4]arenes via Double Bridging of the Upper Rim

Slavik, P.; Eigner, V.; Lhotak, P.
Cryst. Eng. Comm. 2016, 18, 4964-4970
DOI:10.1039/C6CE00314A

Abstract: Direct double meta-mercuration can be used for subsequent bridging of a calix[4]arene skeleton via the installation of ketone moieties. This unprecedented substitution pattern in calixarene chemistry possesses a heavily distorted and rigid cavity capable of interactions with selected molecular guests as documented by binding of a CH₂Cl₂ molecule held in place by an intricate net of 10 specific (halogen bonding and hydrogen bonding) interactions from two neighbouring calixarene molecules

Calix[4]arene Containing a Ureido Functionality on the Lower Rim as Highly Efficient Receptors for Anion Recognition

Klejch, T.; Slavicek, J.; Hudecek, O.; Eigner, V.; Gutierrez, N. A.; Curinova, P.; Lhotak, P.

New J. Chem. 2016, 40, 7935-7942
 DOI:10.1039/c6nj01271j

Abstract: The introduction of nosyl moieties onto the lower rim of the calix[4]arene skeleton led to the formation of compounds immobilised in cone conformations. Subsequent reduction of the nitro group and reaction with aryl isocyanates enabled the construction of new calixarene-based ligands for anion recognition. As proven by NMR and UV/vis titration experiments, diaryl urea moieties with electron-withdrawing substituents on both sides represent very efficient tools for the complexation of selected anions (AcO⁻, BzO⁻, H₂PO₄⁻) even in highly competitive solvents such as DMSO-d₆.