POLY 622 |
| The application of a novel class of amphiphilic, water-soluble diblock copolymers based on 2-oxazoline derivatives with pendant N-heterocyclic carbene (NHC) / palladium catalysts in the hydrophobic block for Heck and Suzuki coupling in neat water is described. In aqueous media, these amphiphilic polymers aggregate to functionalized micelles with palladium complexes in the hydrophobic core, thereby forming a catalytic active nanoreactor. Using these micellar reactors, the catalysis of very hydrophobic substrates in pure water is feasible. Heck coupling reaction of iodobenzene with styrene proceeded rapidly after optimization of various reaction parameters such as the base, the reaction temperature, catalyst amount, and the structure of the polymeric amphiphile. High activities with turnover frequencies (TOF) of up to 2700 h-1 were observed at 110 °C. Furthermore, the Suzuki coupling reaction of phenylboronic acid was studied in detail with different haloarenes (iodobenzene and various bromoarenes). In comparison to Heck reaction the observed catalytic activity is even higher and TOF numbers of up to 5200 h-1 were achieved at 80 °C. Therefore, the presented micellar catalytic system reveals turnover frequencies, which are to our knowledge the highest ever reported for such transformations of very hydrophobic substrates in neat water without the addition of any organic co-solvent. |
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Metal-Containing and Metallo-Supramolecular Polymers and Materials
8:05 AM-12:00 PM, Thursday, August 23, 2007 Westin Boston Waterfront -- Stone, Oral
Division of Polymer Chemistry |