Chemoselective transesterification and polymer synthesis using a zincate complex

Abstract

In this focused review, I present an overview of our recent research on the zincate complex dilithium tetra-tert-butylzincate (TBZL)-catalyzed ring-opening polymerization (ROP) of e-caprolactone, efficient acylation and transesterification of alcohols with vinyl acetate and carboxylic esters, and polymer synthesis with a high transesterification ability. In the first part of this report, the ROP of e-caprolactone catalyzed by TBZL in toluene is described. In a subsequent study of the ROP of e-caprolactone in the presence of 2-hydroxyethyl methacrylate (HEMA), TBZL was found to act not only as an anionic initiator but also as a transesterification catalyst. In the second part of this report, the acylation and transesterification of alcohols with vinyl acetate and carboxylic esters catalyzed by TBZL are summarized. The acylation proceeded quantitatively at 0 °C within 1 h. A wide range of combinations of esters and alcohols were suitable for the transesterification at 0 to −40 °C. In addition, the transesterification proceeded chemoselectively even in the presence of H2O and amines. Next, TBZL-catalyzed polycondensations of diphenyl carbonate (DPC) with diols are discussed. Irreversible polycondensations catalyzed by TBZL occurred to yield aliphatic polycarbonates under atmospheric pressure. In the last part of this report, the transesterifications of poly(phenyl methacrylate) (PPhMA) side chains with alcohols catalyzed by TBZL are described. The transesterification reaction not only with alkyl alcohols but also with fluoroalcohols occurred. By changing the reaction solvent and temperature, the degree of conversion could be controlled. The present system permits the partial, quantitative, or terminal conversion of polymethacrylates. Our recent studies on the zincate complex dilithium tetra-tert-butylzincate-catalyzed transesterification and polymerization are reviewed. In the first part of this report, the ROP of e-caprolactone catalyzed by TBZL is described. In the second part of this report, the acylation and transesterification of alcohols with vinyl acetate and carboxylic esters catalyzed by TBZL are summarized. Next, TBZL-catalyzed polycondensations of diphenyl carbonate (DPC) with diols are discussed. In the last part of this report, the transesterifications of poly(phenyl methacrylate) (PPhMA) side chains with alcohols catalyzed by TBZL are described.