TEMPLATE EFFECTS. 7. LARGE UNSUBSTITUTED CROWN ETHERS FROM POLYETHYLENE GLYCOLS: FORMATION, ANALYSIS, AND PURIFICATION

Article abstract of DOI:10.1016/S0040-4020(01)80080-6

Through the reaction of polyethylene glycols with tosyl chloride and heterogeneous KOH in dioxane not only coronands from <12>crown-4 to <24>crown-8 can be obtained but also larger homologues.A systematic investigation has shown that: i) <27>crown-9 and <30>crown-10 can be formed from nona- and deca-ethylene glycol, respectively, and isolated in pure form; ii) the whole series of polyethylene glycols from tri- to deca-ethylene glycol yields not only the corresponding crown ethers but also higher cyclooligomers that can be analyzed up to about <60>crown-20 by glc: in particular <36>crown-12 and <48>crown-16 were obtained from tetraethylene glycol and purified by column chromatography on cellulose; iii) the reaction, as applied to commercial mixtures of polyethylene glycols (from PEG 200 to PEG 1000), gives fairly high yields of crown ethers also in the region of large ring sizes.The contribution of the template effect of K(+) ion and the cyclooligomerization reactions for the various ring sizes are discussed.