Chemical upcycling of poly(bisphenol A carbonate) to vinylene carbonates through organocatalysis

Abstract

The chemical depolymerisation of poly(bisphenol A carbonate) (BPA-PC) was studied using α-hydroxyketones as nucleophiles to give bisphenol A as the original monomer and the corresponding vinylene carbonates as co-products. The optimisation revealed that 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) is an efficient organocatalyst to perform this reaction under mild conditions (25 °C in 2-MeTHF). The success of TBD was attributed to the fact that it can both activate α-hydroxyketones and BPA-PC, through hydrogen bonding. The substrate scope was then investigated with a range of α-hydroxyketones to give vinylene carbonates (symmetrical and unsymmetrical, aromatic, heteroaromatic and alkyl) with moderate to high yields (30–97%, 13 examples). Scale-up experiments were also conducted to highlight the synthetic utility of this method. Finally, it was demonstrated that vinylene carbonates can be produced from waste polycarbonate contained in compact disks (CDs) and other BPA-PC containing materials, thus providing a safe and economical access to these species.