Organocatalytic Synthesis of Poly(thiocarbonate) from Xylose and Carbonyl Sulfide

Abstract

Facile synthesis of sulfur-containing polymers from renewable chemicals or the waste of petrochemical resources remains a grand challenge. Here, we report organocatalytic alternating copolymerization of carbonyl sulfide (COS) and D-xylose oxetane (XO) to produce poly(thiocarbonate). COS is industrially released as a waste gas, while XO is synthesized from biorenewable xylose with an E factor of 2.31 and an atom economy of 30%. The commercially available binary organocatalyst system consists of alkyl borane (as a Lewis acid) and a quaternary ammonium salt (as an initiator). Density functional theory calculations suggest that the Lewis acid of borane can activate XO and stabilize the growing anion. The catalyst system exhibits high activity with turnover frequencies of up to 70 h −1 at 25 °C, affording poly(thiocarbonate) with a welldefined structure, complete alternating sequence, >99% chemoselectivity, and regioregular polymer backbone composed of head-to-tail linkages. Terpolymerization of XO, propylene oxide, and COS yields a series of poly(thiocarbonate) with a largely tunable T g ranging from 26 to 138 °C.