Synthesis of TADDOL-derived crown ethers

Four cyclic polyethers incorporating one (4R,5R)-2,2-dimethyl-alpha,alpha,a lpha',alpha'-tetraphenyl-1,3-dioxolane-4,5-dimethanol (2,2-dimethyl-TADDOL) unit and with ring sizes of 14-crown-4, 17-crown-5 and 20-crown-6 were syn thesized. The synthesis of the corresponding bis(TADDOLo)-22-crown-6 ether was attempted, but the 11-crown-3 ether was obtained instead. The structure s of the side-products were elucidated and their formation is rationalized on the basis of template and steric effects. The ability of the crown ether s synthesized, distorted by the presence of the TADDOL unit in the ring, to form host-guest complexes with alkali metal cations is briefly discussed.