Calix arene thiourea derivative

From a series of fluorinated calixarenes, functionalised at the lower rim to contain oxygen, nitrogen and sulphur donor atoms, a calix[4]arene thiourea derivative proved to be an effective Au extractant in unmodified SC-CO2. 

Calix[4]arene-based bifunctional thioureas, derived from trani-l,2-diaminocyclo-hexane, have been reported to catalyse the Michael addition of a,a-disubstituted aldehydes to maleimides, giving (292) with <98%... 

Around the same time as this, Reinhoudt developed a calix[4]arene system with only two urea or thiourea functionalities attached on opposite faces 70-72 [167]. These less substituted systems display both inter- and intramolecular hydrogen bonding as a result of the calixarene adopting a pinched cone conformation (demonstrated by the use of NOESY NMR). In some spectra it is impossible for the connectivities to be made within a single molecule, so the only possibility left is that dimerisation occurs. As with the initial experiments of Rebek and Bohmer, the extent of hydrogen bonding was observed to be solvent dependent. Concentration dependant FTIR was also used, to observe the effects on the NH stretching vibrations, but no concentration dependence was observed. Of the three urea derivatives used, only 72 showed no evidence of dimerisation... 

---