Polymeric transfer reagents advantages

An advantage of polymer-based reagents is that both the excess and the spent reagent are easily separated from the product. Bruno Linclau of the University of Southampton has reported J. Org. Client. 2004, 69,5897) the preparation of a polymer-bound carbodiimide. Exposure of the polymer to alcohol gives a family of O-alkylisoureas that smoothly convert carboxylic acids to the corresponding esters. Methyl, benzyl, ally and p-nitrobenzyl transfer smoothly. The polymeric (-butyl reagent could not be prepared. 

Poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymers were first applied successfully as a phase transfer reagent in two-phase Suzuki carbon-coupling reactions. The use of such polymeric reagents in micellar and phase-transfer systems has the advantage that they can be separated easily from the reaction mixture by means of a membrane [138]. 

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