Phase-transfer catalytic activity of polymer-supported macrocyclic polyethers

Polymer-supported crown-ethers 9 and 11 (4.5-62% ring substitution) have been obtained by the reaction of 1% crosslinked chloromethylated polystyrenes with (hydroxymethyl) and (ω-hydroxynonyl)-18-crown-6, respectively. (Hydroxymethyl) and (ω-hydroxynonyl) [2.2.2] cryptands have also been prepared and linked in a similar way to afford catalysts 10 and 12 (3-6% ring substitution). Condensation of (aminomethyl) and (ω-aminodecyl [2.2.2] crypands with carboxylated 1% crosslinked polystyrene gave catalysts 13 and 14 (5-20% ring substitution). Phase-transfer catalytic activity of polymer-supported crown-ethers and cryptands has been tested in anion promoted nucleophilic aliphatic substitutions, and compared with that of polymer-supported phosphonium salts. The results indicate that catalytic activity of crown-ethers strongly depends on the combination of three parameters: the nature of the nucleophile, the percent ring substitution, and the presence of a spacer chain. Catalytic activity of cryptands is higher than that of crown-ethers and quaternary salts with similar percent ring substitution. It is much less dependent on the nature of the anions and on the presence of a spacer chain. As for the related quaternary salts, phase-transfer reactions promoted by polymer-supported crown-ethers and cryptands follow a mechanism identical with that observed for soluble catalysts: the reactions occur in the organic shell surrounding a complexed ligand; anions are exchanged at the water-organic solvent interface, the exchange not requiring the concomitant transfer of cationic counterparts.