Heck and Suzuki coupling reactions in water using poly(2-oxazoline)s functionalized with palladium carbene complexes as soluble, amphiphilic polymer supports

Abstract

This paper describes the application of a novel class of amphiphilic, water-soluble diblock copolymers based on 2-oxazoline derivatives with pendant N-heterocyclic carbene/palladium catalysts in the hydrophobic block for Heck and Suzuki coupling in neat water. Heck coupling reaction of iodobenzene with styrene proceeded rapidly after optimization of various reaction parameters such as the base, the reaction temperature and the catalyst amount. High activities with turn over 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). 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 turn over frequencies which are the highest ever reported for such transformations in neat water without the addition of an organic cosolvent.