Reactivity of poly(alkoxycarbonylmethylene)s under basic conditions: alkylation of main chain carbon atoms via a ketene silyl acetal-type intermediate and cleavage of the carbon–carbon main chain

Abstract

The reactivities of poly(alkoxycarbonylmethylene)s under basic conditions are described. The reactions of poly(ethoxycarbonylmethylene) (polyEDA′) and poly(benzyloxycarbonylmethylene) (polyBDA′) with a mixture of lithium diisopropylamide and trimethylsilyl chloride transformed a part of the repeating units (ca. 25 and 50 mol% for polyEDA′ and polyBDA′, respectively) into ketene silyl acetal frameworks. The ketene silyl acetal units were partially alkylated by the reaction with a mixture of tetrabutylammonium fluoride (TBAF) and an electrophile (methyl iodide and benzyl bromide), affording poly(substituted methylene)s with quaternary carbon atoms in the main chain, with the highest incorporation of 13 mol% being attained in the methylation of silylated polyBDA′. TBAF was found to effectively cleave carbon–carbon bonds in the main chain of polyEDA′ and polyBDA′ at room temperature for 1 h, yielding poly(alkoxycarbonylmethylene) oligomers with well-defined chain end structures with a much higher frequency of cleavage than that observed with their vinyl polymer counterparts, poly(alkyl acrylate)s.