Polymer support reactants

A quaternary ammonium hydroxide ion exchange resin 6 was shown to sequester phenols, hydroxypyrazoles, and other weakly acidic heterocycles.25 The sequestered nucleophiles could also be used as polymer-supported reactants. Similarly, the guanidine-functionalized resin 7 was also shown to be a useful capture agent for weakly acidic nucleophiles, including phenols and cyclic iV-acyl sulfonamides.26... 

Polymer-supported reactants are most useful for cases where reactant byproducts would otherwise be difficult to sequester. Recycling of the... 

A variant of the trapping experiment, which physically excludes the possibility of the direct reaction of the trap with reactant, is found in the three-phase test [24]. This exploits the availability of an increasing range of polymeric solid supports (PS in Fig. 9.7) to which reactants and trap maybe separately attached. The direct reaction between the solid-supported trap and solid-supported reactant is not anticipated, but control experiments to establish this are advisable. The formation of the trapping product (Q) when the polymer-supported reactant and polymer-supported trap are dispersed together in a solution under conditions where the suspected intermediate would be released from the reactant is then clear evidence... 

In spite of highly stereospecific coupling reactions, the outcome of coupling is not completely specific and anomeric products are formed. In general the stereospecificity of a reaction is somewhat lowered by use of polymer-supported reactants. It is perhaps for this reason that no synthesis of a disaccharide with an o-glycoside bond has been made. 

Polymer chemical reagent Polymer supported catalysts are a particular attractive type of polymer-support reactant, because a relatively small amount is used to chemically transform a relatively large amount of substrate. After the reaction, the polymer-supported species can be separated without difficulty from low molecular weight species in solution. Separation is most readily achieved if the polymer is cross-linked, since it is then insoluble in all solvents. 

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