A Simple, Effective, and Selective Synthesis Route without Template Effect (Part II) for [2 + 2] Difunctional 28-Membered Macrocyclic Ethers Based on Benzoxazine Dimers and Its Inclusion Phenomena with Metal Ions

Abstract

Abstract A macrocyclic ether produced from benzoxazine dimers and ditosylated diethylene glycols is a model to show that the cyclization occurs when intramolecular hydrogen bond of benzoxazine dimer is eliminated in the strong basic condition via a selective [2 + 2] pathway without metal template effect. Macrocyclic ethers perform inclusion phenomena at host-guest stoichiometric ratios of 1:1, and 2:1 depending on the type of metal ion, as clarified by UV and 1H NMR.