Synthesis of 7,8,9,10,11,12,20,21,22,23,24,25-dodecahydrodibenzo[b,m]-[1,4,12,15]tetraoxacyclodocosin, a crown ether
Abstract
A number of symmetrical diesters and an unsymmetrical type have been synthesised from pyrocatechol. Under conditions in which intramolecular acyloin formation was anticipated the product from one symmetrical compound, ethyl 4-(o-ethoxycarbonylpropoxyphenoxy) butyrate, was a cyclic bis-β-keto-ester resulting in reasonable yield from intermolecular Dieckmann cyclisation. Hydrolysis to the 9,22 diketone, and its reduction to 7,8,9,10,11,12,20,21,22,23,24,25-dodecahydrodibenzo [b,m][1,4,12,15] tetraoxacyclodocosin ‘dibenzo-22-crown-4,’ proceeded smoothly. An unsymmetrical intermediate, methyl 4-(o-ethoxycarbonylmethoxypropylphenoxy) butyrate, was prepared for similar cyclisation and in preliminary experiments appeared to give acyloin and β-keto-ester products. The method represents a different approach to crown ether systems of certain types.
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