Synthesis of potential receptor molecules by combination of upper-rim-functionalized calixarenes and partly bridged resorcinarenes

Article abstract of DOI:10.1002/recl.19951140306

Combination of upper-rim-1,3-difunctionalized calix<4>arenes 14, 16, and 18 with tribridged resorcinarenes 4 and 6 and A,C-di-bridged resorcinarenes 10 and 13 yields both 1/1 calix-resorcinarenes (22-24) and 2/1 calix-resorcinarenes (25, 26). 1/1 Calix-resorcinarene 22 mainly exists as one conformer (a), but at low temperatures (-60 deg C) very small amounts (<5percent) of a second conformer (b) can be observed.Both conformers equilibrate via rotation about one of the C(arene)-N bonds, with an activation free energy (ΔG(excit.)) of 13 kcal/mol. 2/1 Calix-resorcinarenes 25 and 26 are more flexible and exist as a mixture of conformes.In order to be able to rigidify the structure of 2/1 calix-resorcinarenes via rigid spacers between the calix<4>arene fragments, 1,3-diaminocalix<4>arene derivatives 31, 32, and 34 were synthesized carrying nitro, carboxylic ester, and cyano groups at the unsubstituted aromatic rings.With these calix<4>arene derivatives, three new, functionalized 2/1 calix-resorcinarenes 35-37 have been synthesized.