Versatile syntheses of hemi-cryptophanes and a metallo-cryptophane from a hexa-functionalized C3v -symmetrical tribenzotriquinacene (TBTQ) derivative.

A number of three-fold C3v -symmetrical tribenzotriquinacene (TBTQ) cavitands were synthesized by a "metamorphosis-to-half" strategy, employing six-fold etherification reactions between the hexakis(chloromethyl)-TBTQ intermediate 2 a and various 5-functionalized resorcinols. X-ray structure analyses of single crystals of the cavitands revealed limited rotational flexibility of the resorcinol bridging units, which enables an apical, nearly co-axial orientation of the three functional groups and, as a consequence, the construction of nanoscale cage-like molecules via covalent or coordination bonding. On this basis, two TBTQ-based hemicryptophanes were prepared from the TBTQ cavitands via covalent bond formation in good yields. A dumbbell-shaped TBTQ-based metallo-cryptophane was also synthesized in 34 % yield by a solvothermal reaction between cadmium nitrate and two equivalents of the TBTQ-cavitand triacid, as confirmed by single-crystal X-ray diffraction and MALDI-ToF mass spectrometry.