Alternating Copolymerization of Ethylphenylketene with Benzaldehyde:  Solvent- and Additive-Controlled Stereospecific Formation of Polyester

Abstract

Copolymerization of ethylphenylketene with benzaldehyde by butyllithium proceeded in a perfect 1:1 alternating manner to afford the corresponding polyester, of which the repeating unit has two adjacent chiral centers. The relative stereochemistry between these two chiral centers was controlled by solvents (tetrahydrofuran or toluene) and additives such as (-)-sparteine or diethylzinc, and the resulting diastereoselectivity, erythro-configuration:threo-configuration, was controlled in a range of 80: 20 to 12:88. These diastereomeric ratios were determined by HPLC analysis of the diols, which were obtained by reductive degradation of the polyester with maintaining the configuration of the repeating unit. The more polar diol was converted to the corresponding cyclic carbonate, and a single crystal of it was successfully analyzed by X-ray crystallography to determine its configuration as a threo one. The threo-rich polymer was less soluble, more thermally degradable, and denser than the erythro-rich polymer.

C‐reactive protein as a regulator of autoimmunity and inflammation

“…As shown in Figure 1(b,c), there exists a pair of enantiomers that have the opposite sign for the chirotopic centers in the main chain. The alternating copolymerization of ketene with aldehyde, which is not discussed in this article, is another interesting example of asymmetric polymerization 16…”

Stereocontrolled anionic alternating copolymerization of ethylphenylketene with benzaldehyde by a bisoxazoline ligand

“…Diastereoselectivity of the polymer main chain was determined by HPLC analysis of the diol 2, obtained by reductive degradation of the polymer: IR (KBr): 1737. 1…”

“…To clarify the effect of t Bubox on stereoselectivity, it was compared to (-)-sparteine, which proved to be an effective ligand for stereoselectivity in our previous study. 1 Diastereoselectivity was determined by HPLC analysis of diol 2, obtained by reductive degradation of the resulting polymer. The relative stereochemistry of the polymer main chain has already been assigned; from this, the diol was converted to the cyclic carbonate, and its single crystal was analyzed by X-ray crystallography.…”

“…The relative stereochemistry of the polymer main chain has already been assigned; from this, the diol was converted to the cyclic carbonate, and its single crystal was analyzed by X-ray crystallography. 1 Table 1 summarizes the results and conditions of the polymerization under various conditions. Monomer consumption was confirmed from the disappearance of the characteristic yellow color of EPK in the system.…”

“…Previously, we have reported the stereospecific synthesis of polyester by the anionic alternating copolymerization of ethylphenylketene (EPK) with benzaldehyde (BA), with n-butyllithium as an initiator. 1 The repeating unit of the resulting polyester had two adjacent chiral centers, and their relative stereochemistry could be controlled by additives such as a Lewis base or a Lewis acid and solvents such as tetrahydrofuran (THF) and toluene. The relative stereochemistry of the repeating unit remarkably influenced the physical properties of the polymers, such as the solubility, the thermal properties, and the density.…”