Temperature-Dependent Reversal of Enantiomer Selectivity in the Complexation of Optically Active Phenolic Crown Ethers with Chiral Amines.

Phenolic crown ethers (S,S)-1, (R,R)-2, (S,S)-3 and (S,S)-4 were prepared in enantiomerically pure forms; the enantiomer selectivities of crown ethers (S,S)-1 and (R,R)-2 in complexation with 2-aminopropan-1-ol reversed at ca. 6 °C and increased with increasing temperature above the isoenantioselective temperature.