Chemistry Letters, Vol.32, No.5, 432-433, 2003
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
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 H-1 NMR.