POLYMER-SUPPORTED PHASE-TRANSFER CATALYSTS - HIGH CATALYTIC ACTIVITY OF AMMONIUM AND PHOSPHONIUM QUATERNARY-SALTS BONDED TO A POLYSTYRENE MATRIX

The synthesis of tetraalkylammonium and tetraalkylphosphonium salts immobilized on a 2% cross-linked polystyrene matrix is described. Under optimized reaction conditions, the catalytic activity of these salts is comparable with that of the best soluble phase-transfer catalysts. The following factors are significant: (1) high lipophilic character and a topology ensuring enough separation between the anion and the cationic center; (2) a long spacer chain allowing the catalytic site to protrude into the reaction medium; (3) porosity of the resin; (4) highly efficient, turbulent stirring, in order to avoid diffusion control. The relative importance of the latter depends on the amount of cross-linking. Reactions follow pseudo-first-order kinetics, and rates are linearly dependent on molar equivalents of the polymer-supported catalyst. The kinetic behavior, the almost exclusive O-alkylation of phenols, and the hydration numbers of halides bonded to quaternary groups strongly support the hypothesis that reactions occur in an organic shell surrounding the catalytic site. Some examples of applications of polymer-supported phase-transfer catalysts to organic syntheses are also reported. © 1979, American Chemical Society. All rights reserved.