The First Synthesis and Characterisation of Elusive cone 1,2-Diformyl Tetralkoxycalix[4]arenes and their Derivatives

The synthesis and isolation of elusive tetralkoxycalix[4]arenes in the cone conformation and bearing two formyl groups in proximal (1,2) positions at the upper rim are described for the first time. They were obtained as a mixture with the distal (1,3) regioisomers by optimizing the Gross formylation reaction on the tetralkoxycalix[4]arenes. After reduction to the corresponding alcohols, the compdounds could be isolated and oxidized to 1,2-diformyl and 1,2-diacid tetralkoxycalix[4]arenes. These 1,2-difunctionalized derivatives are useful intermediates for the synthesis of calixarene-based molecular receptors having proximal binding groups.