Synthesis of 3,3-di(ethoxycarbonyl)-1-vinylpyrrolidin-2-one and determination of its reactivity ratios with 1-vinylpyrrolidin-2-one

Novel 1-vinylpyrrolidin-2-one (VP) derivatives, namely 3,3-di(ethoxycarbonyl)-1-vinylpyrrolidin-2-one (DEVP) and 3-(ethoxycarbonyl)-1-vinylpyrrolidin-2-one (EVP), were obtained through a two-step synthetic pathway involving the abstraction of a hydrogen atom cc to the lactam C=O, followed by condensation with ethyl chloroformate. By properly selecting the reaction conditions, DEVP could be obtained in high yields, through a straightforward purification procedure. Both DEVP and EVP were converted to sodium 1-vinylpyrrolidin-2-one-3-carboxylate (VP-COONa) by saponification of the ester group, followed by decarboxylation reaction in the case of DEVP. All monomers were homo- and copolymerized with VP by radical polymerization, the structure of the polymer obtained was determined by means of H-1 and C-13 NMR spectroscopy, and molecular weights were analyzed by means of size exclusion chromatography. The resultant DEVP- and EVP-based polymers also underwent hydrolysis with alkali solutions, followed by decarboxylation reaction in the case of DEVP units, which led in all cases to one carboxylate function linked to the lactam ring. The reactivity ratios for the copolymerization of DEVP with VP were determined in methanol solution according to the Kelen-Tudos procedure, through polymerization experiments performed at different feed, in which compositional drifts were followed by monitoring monomer conversions by means of H-1 NMR spectroscopy. The values of the reactivity ratios obtained were r(DEVP) = 0.63 and r(VP) = 0.33. The validity of these parameters was checked by means of the classical Skeist equation.