The nucleophilic coupling of the secondary nitrogen atoms of the mixed-donor crown ethers [16] aneS4N,[15] aneS4N,[15] aneO4N,[15] aneO2S2N and [12] aneS3N to an epoxide proceeds in an unexpected manner. The degree of coupling appears to be inversely related to the number of thioethers in the crown ether. Two possible explanations were considered:(i) steric factors affecting the accessibility of the lone pair on the secondary ...
