The use of 18-crown-6 as an ionizable phase label for the expedited synthesis of small molecules

A silica-supported propylbenzenesulfonic acid ion-exchange column was treated with a methanol solution of potassium carbonate to give the corresponding potassium sulfonate salt. This column was shown to effectively sequester 18-crown-6 and its derivatives presumably due to chelation of the macrocyclic ether with the ionically bound potassium cation. This phenomenon was also observed to a lesser extent with ammonium ion but not with other cations such as lithium and cesium. This crown ether technique was then used to facilitate the purification of an amidation reaction.