Polymer-Bound Palladium Complexes of 2-Pyridyldiphenylphosphine

Significance

The insoluble polymer-supported 2-pyridyldiphenylphosphine ligands have been prepared. Lithiation of 2-bromopyridine followed by transmetallation with zinc chloride in pyridine gave the cyclic 2-pyridyl zinc dimer 2, which was quenched with dichlorophenylphosphine to afford 2-pyridylphenylchlorophosphine (3). The polymerizable styryl group was introduced by reaction of 3 with styryl magnesium chloride. The copolymerization of 4 with styrene was carried out in benzene using 2,2′-azobis(2-methyl)propionitrile (AIBN) as a radical initiator to give polystyrene-supported 2-pyridyldiphenylphosphine 5. Similarly, copolymerization of 4 with methyl methacrylate gave 2-pyridyldiphenylphosphine-loaded copolymer 6. Polyvinylpyridine-supported 2-pyPPh₃ 7 was prepared by copolymerization of 4-vinylpyridine with 4 in the presence of AIBN. Palladium complexes of 5-7 have shown to form active and selective catalysts for the alkoxycarbonylation of terminal alkynes.