Mechanism of Reactions Promoted by Polymer-Supported Phase-Transfer Catalysts

Article abstract of DOI:10.1021/jo00150a012

Kinetic measurements indicate that the ratio of C- vs.O-alkylation of β-naphthoxide is not a reliable polarity test for polymer-supported phase-transfer catalysis because of the competitive noncatalyzed reactions.A reliable test is the C/O-alkylation of phenoxide.Reactions carried out in toluene-water in the presence of stoichiometric amounts of polystyrene-supported quaternary phosphonium salts 2 and 3 afford only O-alkylation products.Stoichiometric reactions give significant amounts of C-alkylation with 2 or 3 in aqueous ethanol or with immobilized polar catalysts 4 and 5 in toluene-water.Hydration measurements agree with the essentially hydrophobic character of polystyrene-supported phosphonium catalysts 2 and 3.These results confirm our previous conclusion that phase-transfer catalysis follows identical mechanisms both in the presence of soluble and polymer-supported catalysts.In the latter case the reaction should occur within an organic solvation shell firmly surrounding the catalytic site, rather than in an aqueous solvation sphere or at the interface.