meta-Bridged calix[4]arenes prepared by Friedel–Crafts alkylation

Abstract

By applying electrophilic aromatic mercuration of calix[4]arene the introduction of substituted hydroxymethyl groups at the meta position of the basic skeleton has been achieved. Subsequent intramolecular Friedel–Crafts alkylation led to a novel type of bridged calix[4]arenes with additional symmetrically substituted methylene bridges connecting to the neighbouring aromatic units. Additionally, this new efficient synthetic pathway was also used for the preparation of a double bridged analogue. These compounds with rigidified cavities can complex cations and neutral compounds using CH–π and/or cation–π interactions as demonstrated by ¹H NMR titration experiments.