Synthesis of the First Calix[6]crypturea via a Versatile Tris-azide Precursor

Various nitrogenous calix[6]arene based receptors have been synthesized in one step from a new C_3v symmetrical calix[6]arene intermediate decorated with azido groups. Hence, the first calix[6]crypturea has been obtained in high yield through a unique one-pot process consisting of a domino Staudinger/aza-Wittig reaction followed by a [1 + 1] macrocyclization reaction with a tripodal amine. The conformational properties and some of the host−guest properties of the new calix[6]arene derivatives have been studied by NMR spectroscopy.