The Synthesis of Unsubstituted Crown Ethers by the Reaction of Oligoethylene Glycols with Arenesulfonyl or Alkanesulfonyl Chlorides

A new facile method of synthesizing crown ethers from oligoethylene glycols by treating them with arenesulfonyl or alkanesulfonyl chlorides in the presence of alkali metal hydroxide or alkoxide was described. 15-Crown-5 and 21-crown-7 were synthesized from pentaethylene glycol and heptaethylene glycol respectively in good yields, while 18-crown-6 was obtained from both hexaethylene glycol and triethylene glycol. Although the main product was 24-crown-8 in the reaction of tetraethylene glycol/TsCl/Na(K)OH in dioxane, 12-crown-4 was obtained in a moderate yield from the reaction of tetraethylene glycol/benzenesulfonyl chloride/t-BuOLi in t-BuOH. Furthermore, the analogous treatment of PEG 200 afforded a mixture of 15-, 18-, 21-, and 24-crown ethers. The reaction conditions were investigated, and the scope of the reaction was discussed.