Odd-Numbered Oxacalix[<i>n</i>]arenes (<i>n</i> = 5, 7): Synthesis and Solid-State Structures

The critical synthetic access to odd-numbered calix[n]arenes has evidently resulted in less attention for these macrocycles, although specific molecular recognition phenomena have been observed for some of them. A straightforward fragment coupling approach has been designed, applying kinetically controlled nucleophilic aromatic substitution reaction conditions, affording odd-numbered oxacalix[n]arenes (n = 5, 7) selectively in high yields. The solid-state conformational behavior and the oxacalix[n]arene cavity size were explored by single-crystal X-ray diffraction studies.