There is much interest in preparing polymeric reagents including types which can subsequently release an active reagent hydrolytically. We are reporting on our work in this area because we feel it should be useful to other workers, especially in the medical field *). Our initial work involved the conventional synthetic approaches such as the use of acryloyl chloride to make acrylic esters or N-substituted acrylamides, followed by suitable copolymerization schemes. This can be a very time consuming and very limited procedure. An alternative was to start with a reactive polymer such as the various copolymers of maleic anhydride, but there are complications. The reaction with an amine gives not only amide but also ammonium salt which for many applications has to be removed. Poly(acryloy1 chloride) has complications arising from anhydride formation. The amide or ester groups in these systems have neighboring carboxylate groups which can give rise to instabilities or abnormal reaction rates which are not always wanted2). We selected a synthetic scheme to prepare polymeric reagents which would alleviate many of the difficulties and limitations discussed above.The system we decided upon was the polymeric oxazolone route. Oxazolones (or azlactones) have a special type of anhydride group which is not only quite reactive but also reacts by addition with no by-products. The syntheses of 2-vinyl-5-oxazolone monomers (1) have been described previo~sly~-'~). Although these monomers can be used to prepare novel substituted acrylamide monomers@, we encountered difficulties due to unfavorable rearrangements'**), including a dimerization which can occur on standing". In both of these side reactions the presence of active hydrogen is necessary so we devoted our efforts to oxazolones which are fully substituted in the 4-position lo).
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