Synthesis of new crown ether compounds
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In 1967, Pedersen published the first practical synthesis of a variety of cyclic polyether compounds and assessed their complexation abilities for alkali and alkaline-earth metal ions. As shown in Equation 1.2, when Pedersen tried to prepare bisphenol 4 from bis(2-chloroethyl) ether and monotetrahydropyranylprotected catechol, which was contaminated with 10% of unprotected catechol, a small amount of white crystalline solid with a silky, fibrous nature was obtained as a by-product. The structure of this by-product was deduced to be crown ether 5 by elemental and mass spectroscopic analysis. Pedersen found that the yield of crown ether 5 could be increased to 45% when pure catechol was utilized as a reactant. Subsequently Pedersen prepared more than 60 macrocyclic polyethers and investigated the formation of complexes between the cyclic polyethers and metal salts. For his work, Pedersen together with Cram and Lehn was awarded the 1987 Nobel Prize in Chemistry.