Polymer-supported palladium-catalysts

Scheme 7.119 Suzuki coupling utilizing a polymer-supported palladium catalyst.

There was recently developed polymer-supported palladium catalyst that can be used in aqueous medium and can be recovered for reuse simply by filtration [2751. To avoid precipitation of insoluble palladium black on the polymer support, a quite stable palladium complex 6 is proposed (Scheme 73) [276, 277]. Mathey reported that their complex with tetraphosphole-based macrocyclic ligand is even more stable and good for reuse (Structure 2) [278]. 

Rapid and efficient Suzuki coupling of protoxygencol has been developed using polymer-supported palladium catalysts under microwave conditions at 110 °C within 10 min. in the synthesis of various benzolidines [15]. Radical cyclization of resin-bound N-(2-bromophenyl)acrylamides using Bu3SnH proceeded smoothly in DMF or toluene as solvent under the action of microwave irradiation for preparation of 2-oxindoles as illustrated in Scheme 10.9. This method is superior to conventional solution synthesis [16]. 

A. Datta, K. Ebert, H. Plenio, Nanofiltration for homogeneous catalysis separation Soluble polymer-supported palladium catalysts for Heck, Sonogashira, and Suzuki coupling of aryl halides, OrganometaUics 22 (2003) 4685-4691. 

Grigg, R. and York, M. (2000) Bimetallic catalytic cascade ring-closing metathesis-intramolecular Heck reactions using a fluorous biphasic solvent system or a polymer-supported palladium catalyst. Tetrahedron Lett., 41, 7255-8. 

Carbonylation ofAllyl Halides. Polymer-supported palladium catalysts are also used to catalyze the carbonylation of allyl halides to form butenoic acid under mild conditions (40 °C, 1 atm) in an aqueous NaOH or two-phase (aqueous NaOH-CeHe) medium according to the following reaction ... 

Polymers, such as poly(N-vinyl-2-pyrrolidone) (PVP), polyacrylamide (PAA), modified poly(2,6-dimethyl-l,4-phenylene oxide) (PPO), and polysulfone (PSF) are used to prepare polymer-supported palladium catalysts. As the data summarized in Table 5, the polymer-supported Pd catalysts are very active in the carbonylation of allylbromide. They are much more active and efficient than the homogeneous palladium catalyst, PdCl2(P(C6H5)s)2. The higher activity of the polymer-supported palladium catalyst possibly results from the increased... 

Utilization of a polymer-supported palladium catalyst in the presence of phosphine ligands, TsOH, and LiCl significantly improved the regioselectivity on the carbonylation of 1-arylethanol to 2-arylpropionic acids (Scheme 11). ... 

Ananikov VP, Kabeshov MA, Beletskaya IP. The first example of polymer-supported palladium catalyst for stereoselective S-S bond addition to terminal alkynes. Synlett 2005 1015-1017. 

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