Stereoselective polymerization has long been a central research focus in polymer science because tacticity plays a crucial role in regulating the physical properties and functions of vinyl polymers. However, synthetic strategies that enable control over both isotacticity and syndiotacticity remain limited. Herein, we report an impact of an intramolecular non-classical hydrogen bond between the vinyl and pendant groups in the monomer on tacticity-controlled polymerization. A vinylboron monomer, in which the boron atom is protected by an anthranilamide bearing a tetrahydrofuran (THF) ring with a chiral center, undergoes syndio-specific polymerization, and the subsequent oxidation of the polymer side chains afforded syndiotactic poly(vinyl alcohol)s (PVAs, rr: up to 63%). Computational studies suggest the hydrogen bond between vinyl proton and oxygen in the THF ring plays a key role in syndiotactic regulation. The interpretation is further supported by a contrasting result obtained by replacing the oxygen atom in the THF ring with a methylene group, which leads to the formation of isotactic PVA (mm: 71%).
Suzuki et al. (Mon,) studied this question.