Polystyrene-bound palladium catalysts

Thus, by using a mixture of the Grubbs catalyst 6/3-13 and Pd(OAc)2/PPh3, 6/3-84a was transformed into 6/3-85a in 65% yield. With the polystyrene-bound palladium catalyst 71 % yield was obtained in contrast, the use of a biphasic system... 

Microwave-assisted Suzuki coupling using a reusable polymer-supported palladium complex has been achieved in a more recent study [135]. The reaction mixture was treated with the polystyrene-bound palladium catalyst and irradiated in an open flask for 10 min in a domestic microwave oven (Scheme 16.88). After cooling, the mixture was filtered and the catalyst extracted with toluene and dried. The recycled polymer-bound catalyst can be reused five times without loss of efficiency. 

A useful polystyrene-bound palladium catalyst has been developed for use in Heck-type coupling reactions [(193)— (195) ... 

A polyethylene glycol-polystyrene graft copolymer palladium catalyst has been used in allylic substitution reactions of allyl acetates with various nucleophiles in aqueous media.58 Another polymer-bound palladium catalyst 40 was developed and used in a Heck coupling of allylic alcohols with hypervalent iodonium salts to afford the substituted allylic alcohols as the sole products under mild conditions with high catalytic efficiency.59 The same polymer-bound palladium catalyst has also been used for Suzuki cross-coupling reactions.60... 

Generally, the activities of polymer-bound palladium catalysts are less than those of unsupported ones, but here too there are exceptions. Kaneda et al reported that PdCl2, on phosphinated polystyrene was more active than the homogeneous situation.Rates were very solvent dependent— hydrogenation of styrene was slow in dimethyl sulfoxide optimum activity was obtained in solvents of moderate coordinating ability (see Table 6). 

Classical Heck reactions can also be conducted with polymer-bound palladium catalysts, for example, with diarylphosphinylated polystyrene. ... 

One of the earliest examples of polystyrene-bound palladium was reported by Tera-sawa and co-workers in 1975, when such a system was used for hydrogenation of olefins and acetylenes and isomerization of double bonds. However, it is not clear if the high activity exhibited by resin-bound catalysts toward hydrogenation was due to the reduced heterogeneous paUadium deposited on the resin. Pittman et al. in 1976 prepared a series of diphenylphosphinated PS-based palladium catalysts and studied their behavior... 

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