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Enhanced Stereocontrol in Disyndiotactic-specific Group Transfer Polymerization of Methyl Crotonate—Stereochemical Evidence of Group Transfer

Group transfer polymerization (GTP) of methyl crotonate was examined by using a ketene silyl acetal with tert-butyldimethylsilyl group in the presence of HgI2 and tert-butyldimethylsilyl iodide as a catalyst and a co-catalyst, respectively. Under optimized conditions, the GTP produced disyndiotactic polymers with narrow molecular weight distribution in quantitative yields. The trialkylsilyl group in the initiator components was found to exert control over the stereochemical process of the GTP; the bulky tert-butyldimethylsilyl group leads to the highest disyndiotacticity. The results provide a direct evidence for the transferring silyl group to be involved in the propagation steps in the GTP.