Fig. 2: Screening results for different catalysts and substrate diols.
(A) Catalyst screening results of liquid-phase, solventless, ambient-pressure oxidative dehydrocyclization of 1,4-BDO to γ-butyrolactone probe reaction for various families of solid catalysts inspired by literature reports. Reaction setup details are provided in Supplementary Fig. S1. Reaction temperature and time for the screens were held constant at 180 °C and 24 h, respectively. The boiling point of 1,4-BDO and γ-butyrolactone are 235 °C and 204 °C, respectively, and the screening temperature was chosen to minimize evaporative losses. (B) Substrate screening results at an arbitrary but constant condition of 180 °C, diol/catalyst mass ratio: 20, reaction time: 24 h, using Cu0.18Ca0.82O MMO catalyst. NMR spectra are shown in Supplementary Fig. S2. Prior literature precedence has already established the direct and indirect polymerization and depolymerization routes of the polymers formed using the lactones shown in (B). We list the representative studies for various (lactone ↔ polymer) systems for the reader’s convenience: γ-butyrolactone ↔ poly(butyrolactone)3, γ-valerolactone and derivatives → corresponding thiolactones ↔ poly(thioesters)87,88, δ-valerolactone ↔ poly(valerolactone)89, methyl-valerolactone ↔ poly(methyl-valerolactone)90,91, (7) hexahydrophthalide ↔ poly(hexahydrophthalide)5. All yields are NMR based. Figure 2A was created in BioRender (https://BioRender.com/e09t023), and is licensed under CC BY 4.0.
