Kinetic Resolution Polymerization Enabled Chemical Synthesis of Perfectly Isotactic Polythioesters.

ABSTRACT

Isotactic polythioesters (PTEs) that are thioester analogs to natural polyhydroxyalkanoates (PHAs) have attracted growing attention due to their distinct properties. However, the development of chemically synthetic methods for preparing isotactic PTEs has long been an intricate endeavour. Herein, we report the successful synthesis of perfectly isotactic PTEs via stereocontrolled ring-opening polymerization. This binaphthalene-salen aluminium (SalBinam-Al) catalyst promoted a robust polymerization of rac-α-substituted-ß-propiothiolactones (rac-BTL and rac-PTL) with highly kinetic resolution, affording perfectly isotactic P(BTL) and P(PTL) with Mn up to 276 kDa. Impressively, the isotactic P(BTL) formed a supramolecular stereocomplex with improved thermal property (Tm=204 °C). Ultimately, this kinetic resolution polymerization enabled the facile isolation of enantiopure (S)-BTL, which could efficiently convert to an important pharmaceutical building block (S)-2-benzyl-3-mercapto-propanoic acid. Isotactic P(PTL) served as a tough and ductile material comparable to the commercialized polyolefins. This synthetic system allowed to access of isotactic PTEs, establishing a powerful platform for the discovery of sustainable plastics.