Polyethyleneimine catalysis

The first section, Chemical Reactions on Polymers, deals with aspects of chemical reactions occurring on polymers—aspects relating to polymer size, shape, and composition are described in detail. One of the timely fields of applications comprises the use of modified polymers as catalysts (such as the immobilization of centers for homogeneous catalysis). This topic is considered in detail in Chapters 2, 3, 8, 9, and 11 and dealt with to a lesser extent in other chapters. The use of models and neighboring group effect(s) is described in detail. The modification of polymers for chemical and physical change is also described in detail in Chapters 2 (polystyrene) 4 (polyvinyl chloride) 5 (polyacrylic acid, polyvinyl alcohol, polyethyleneimine, and polyacrylamide) 6 (polyimides) 7 (polyvinyl alcohol) 8 (polystyrene sulfonate and polyvinylphosphonate) 10 (polyacrylamide) and 12 (organotin carboxylates). 

Meyers WE, Royer GP. Catalysis of para-nitrofluoroacetanilide hydrolysis by an imidazole derivative of polyethyleneimine ghosts. J Am Chem Soc 1977 99 6141-6142. 

Because of this structural characteristics vdiich are much different from those of vinyl polymers, polyethyleneimine (PEI) is eicpected to provide interesting microenvironments for catalysis. Femandez-Prini and Turyn studied the deconq>osition of p-nitrophenyl fhosphate 2 in the presence of polyetih>ieneimine (114). 

Audientic catalysis was found for imidazole-modified polyethyleneimine. Klotz et al. reacted polyethyleneimine with ddoiomethylimidazoie and then remaining primary amines were allqrlated quantitatively with dodecyl iodide 120). 

It would be expected that hydrophobic bonding of a substrate to a polymer carrying catalytic groups could also serve to enhance the catalytic efficiency and an attempt to demonstrate such an effect has recently been described (52). It was found that when p-nitrophenyl laurate was added to polyethyleneimine partially acylated with a long-chain fatty acid, p-nitrophenol was extremely rapidly released. However, it seems likely that this reaction involves aminolysis of the ester rather than catalysis of a hydrolytic process and it remains to be seen whether true catalysis can be achieved in this manner. 

Klotz and co-workers to catalysis by hydrophobic polyethyleneimines con-tinues and a novel application of water soluble microgels containing pendant hydroxamic acid groups is reported. 

As a consequence of showing that alkylated polyethyleneimines can facilitate aqueous biphasic catalysis, we extended the concept by the preparation of a cross-linked polyethyleneimine assembly that encapsulated a polyoxometalate catalyst, which resulted in the Upophiloselective oxidation of secondary alcohols (Scheme 9.17) [152]. Thus, even though reactions were carried out in water, competitive oxidation of a more hydrophobic alcohol in the presence of a hydrophilic alcohol significantly favored the former. The lipophiloselectivity was proportional to the relative partition coefficient of the substrates. 

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