Poly(4-dodecylstyrene) as a phase-selectively soluble polymer support in homogeneous catalysis

Abstract

4-Dodecylstyrene was copolymerized with 4–15 mol% of styrene monomers containing functional groups to synthesize polystyrene-like, alkane phase-selectively soluble polymer supports. Comparison studies of substituted polystyrenes containing dansyl groups showed that dodecyl groups significantly increase the phase selective solubility of a dodecyl-substituted polystyrene analog in the heptane phase of a heptane–acetonitrile mixture versus the phase selective solubility of poly(4-tert-butylstyrene) in this same solvent mixture. Coupling of a 4-dimethylaminopyridine (DMAP) derivative to poly(4-dodecylstyrene) (C₁₂PS) formed a (C₁₂PS)-supported DMAP organocatalyst. This C₁₂PS-bound DMAP catalyst had activity like that of other polymer-supported DMAP catalysts and was fully recyclable in a variety of acylation reactions. Catalyst recycling was effected using a biphasic liquid–liquid separation step after a monophasic reaction. By using a C₁₂PS-supported DMAP catalyst that contained dansyl groups, we were able to show that the C₁₂PS-bound DMAP organocatalyst could be recycled as many as 20 times with catalyst leaching that was as low as 0.002% of the starting catalyst per cycle.