Polymer-supported o-benzyl and o-allylisoureas: convenient preparation and use in ester synthesis from carboxylic acids.

[reaction: see text] Polymer-supported O-methyl, O-benzyl, and O-allyl-isoureas were prepared by copper(II)-catalyzed reaction of polymer-supported carbodiimide with the corresponding alcohols. These polymer-supported reagents were successfully employed to convert a series of carboxylic acids to methyl, benzyl, or allyl esters, in good yields. The products were obtained with high purity (>95% by NMR) after a simple resin filtration-solvent evaporation sequence.