Iron-Catalyzed Direct Synthesis of p-Dioxanone from Commodity Methyl Glycolate and Ethylene Oxide

The development of closed-loop circular polymers presents The development of closed-loop circular polymers presents a promising strategy to mitigate plastic waste and facilitate the transition to a circular economy. Poly(p-dioxanone) (PPDO) is a high-performance, closed-loop recyclable polymer; however, its widespread application is hindered by the challenges associated with the large-scale synthesis of its monomer, p-dioxanone (pDO). In this work, we present a one-pot, direct synthesis of pDO from the commodity chemicals-methyl glycolate (MG) and ethylene oxide (EO). We identify iron chloride (FeCl3) as the most effective catalyst for the tandem ring-opening reaction (ROR) between MG and EO, yielding methyl 2-(2-hydroxyethoxy)acetate (MHEA) as an intermediate, which undergoes self-cyclization to form pDO in a one-pot process. Systematic optimization studies show that the optimal ROR occurs at 0 °C for 1 hour, followed by a two-stage MHEA cyclization (1 hour at 100 °C and vacuum distillation at 100 °C), resulting in a maximum isolated pDO yield of 66%. The purified pDO monomer is a white crystalline solid that is readily polymerizable to high-molecular-weight PPDO. This efficient, green, and atom-economical strategy offers a promising approach for the sustainable and industrial-scale production of pDO, thereby advancing the potential for large-scale applications of PPDO and contributing to the development of a circular plastic economy.