Reduced symmetry triflate-resorcin[4]arenes

Abstract

The synthesis of C2v-symmetric resorcin[4]arenes with four triflate substituents was investigated, and a number of examples were structurally characterised by X-ray crystallography. Starting from a readily prepared resorcin[4]arene octol, the reduction in the symmetry to C2v is achieved via the known regioselective tetra-substitution reaction with tosyl chloride. The remaining four hydroxyl groups can be either converted to triflates, or protected as methoxy groups allowing clean hydrolysis of the tosylates to a tetramethoxyresorcin[4]arene tetrol, ready for further functionalisation including triflate incorporation. Synthesis and structural characterisation of the first octa(triflate)resorcin[4]arene are also reported. Aryl triflates are known to be reactive in a number of cross-coupling reactions, and thus, the triflate-resorcin[4]arenes reported herein are promising precursors for functionalisation of the upper rim of these cavitand hosts.