Synthesis of potential receptor molecules by combination of upper‐rim‐functionalized calix[4]arenes and partly bridged resorcinarenes

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°C) very small amounts ( < 5%) 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 (Δ G ≠ ) of 13 kcal/mol. 2/1 Calix‐resorcinarenes 25 and 26 are more flexible and exist as a mixture of conformers. 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.