meta-Bridged calixarenes prepared by Friedel–Crafts alkylation
By applying electrophilic aromatic mercuration of calixarene 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 calixarenes 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.