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Missing‐Link Macrocycles: Hybrid Heterocalixarene Analogues Formed from Several Different Building Blocks
Author(s) -
Sessler Jonathan L.,
Cho WonSeob,
Lynch Vincent,
Král Vladimír
Publication year - 2002
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/1521-3765(20020301)8:5<1134::aid-chem1134>3.0.co;2-m
Subject(s) - pyrrole , pyridine , chemistry , benzene , crystallography , proton nmr , ring (chemistry) , single crystal , stereochemistry , calixarene , molecule , organic chemistry
The synthesis and structural characterization of hybrid heterocalix[4]arene analogues containing pyrrole, benzene, methoxy‐substituted benzene, and pyridine subunits is described. Macrocycles 1 and 2 , examples of calix[2]benzene[2]pyrrole and calix[1]benzene[3]pyrrole systems, respectively, are synthesized by the condensation of pyrrole and an appropriate phenylbis(carbinol). Macrocycles 3 and 7 , examples of calix[2]benzene[1]pyridine[1]pyrrole and calix[1]pyridine[3]pyrrole, respectively, are synthesized by the use of a carbene‐based pyrrole‐to‐pyridine ring‐expansion procedure. Single‐crystal X‐ray analysis reveals that compounds 1 a, 1 b , and 2 b adopt 1,3‐alternate conformations in the solid state, whereas compounds 3 and 7 display structures that are best described as “flattened partial cones” in terms of their conformation. (Series a refers to pure benzene‐derived systems, whereas series b indicates macrocycles containing 5‐methoxyphenyl subunits). In the solid state, the methoxy‐functionalized macrocycles 1 b and 2 b , and the chloropyridine‐containing macrocycle 7 exist as dimers. In the case of 1 a and 7 , these compounds interact with neutral solvent in the solid state. The conformations of the macrocycles in solution were explored by temperature‐dependent proton NMR and NOESY spectral analysis. At 188 K, macrocycles 1 a and 2 a adopt flattened 1,3‐alternate conformations, whereas macrocycles 3 and 7 exist in the form of flattened partial‐cone conformations. Standard proton NMR titration analyses were carried out in the case of macrocycles 1 a and 2 a , and reveal that at least the second of these systems is capable of binding fluoride and chloride anions in CD 2 Cl 2 solution at room temperature ( K a =571 and 17 M −1 in the case of 2 a and F − and Cl − , respectively).