Heterogeneous palladium-catalysed Catellani reaction in biomass-derived γ-valerolactone

Abstract

Herein, we report the unprecedented use of a heterogeneous palladium catalyst for the step-economical Catellani reaction. The substrate scope with encapsulated Pd(OAc)₂ (Pd EnCat™ 30) or Pd/Al₂O₃ proved to be broad, while the renewable biomass-derived γ-valerolactone (GVL) was identified as an effective reaction medium. Mechanistic studies highlighted the possible heterogeneous nature of the Pd/Al₂O₃ catalyst, while showing that the reaction performed in the presence of Pd EnCat™ 30 is most likely catalysed by leached homogeneous palladium species. The heterogeneous Pd/Al₂O₃ catalyst can be easily recovered at the end of the reaction and efficiently reused in consecutive reaction runs.