Contra-Thermodynamic α,β- to β,γ-Photodeconjugation of an Inert CO₂-Derived δ-Lactone Enables Facile Ring-Opening...

The ring-opening polymerization (ROP) of δ-lactones derived from the telomerization of CO₂ and butadiene offers a platform to valorize cheap and abundant waste products into commercially competitive products. However, the ROP of multisubstituted δ-lactones is often limited by a lack of exergonicity. Here, our team reports the photochemical activation of 3-ethylidene-6-vinyltetrahydro-2H-pyran-2-one (EVP) through base-catalyzed α,β- to β,γ-photodeconjugation, affording 3,6-divinyltetrahydro-2H-pyran-2-one (DVP) with yields up to 97%, where yields are dependent on the pK_a of the catalyst's conjugate acid. Ti(OⁱPr)₄-catalyzed selective ring-opening polymerization results in well-controlled polymerizations with polymer molar masses up to 5 kDa. Thermodynamic analysis of DVP polymerization reveals a ceiling temperature (T_c) of 58 °C, ∼200 °C higher than for EVP, demonstrating how photodeconjugation can be used as a simple tool to improve the polymerization thermodynamics of β-substituted-α,β-conjugated lactones.