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, compounds 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.