Postpolymerization modification of poly(2-alkoxyethoxycarbonylmethylene)s: Efficient formation and reactivity of the ketene silyl acetal repeating units in the polymer main chain

Abstract

Postpolymerization modifications of poly(2-methoxyethoxycarbonylmethylene) (pMEDA’) and poly(2-phenoxyethoxycarbonylmethylene) (pPEDA’) are described. The reactions of these polymers with mixtures of chlorotrimethylsilane (Me3SiCl) and lithium diisopropylamide (LDA) efficiently transformed the alkoxycarbonylmethylene repeating units to ketene silyl acetals to yield a product with up to 93 mol% composition of the latter unit. The ketene silyl acetal composition of the product was controlled by changing the feed ratio of Me3SiCl/LDA with respect to the alkoxycarbonylmethylene unit. Tetrabutylammonium fluoride (TBAF)-mediated benzylation of the highly silylated polymer with benzyl bromide yielded a polymer containing side chain O (major)- and main chain C (minor)-benzylated units along with the unreacted ketene silyl acetal unit. Postpolymerization modifications of poly(2-methoxyethoxycarbonylmethylene) and poly(2-phenoxyethoxycarbonylmethylene) with mixtures of Me3SiCl and LDA efficiently transformed the alkoxycarbonylmethylene repeating units to ketene silyl acetals to yield a product with up to 93 mol% composition of the latter unit. TBAF-mediated benzylation of the highly silylated polymer with benzyl bromide yielded a polymer containing side chain O (major)- and main chain C (minor)-benzylated units along with the unreacted ketene silyl acetal unit.