Bidentate ligand-enabled Wacker-type oxidation of olefins using K2S2O8 as an oxidant

Abstract

Wacker-type oxidation represents a pivotal method for ketone synthesis, yet challenges persist in developing sustainable oxidants and efficient ligands. Herein, we report a highly effective Pd(II)-catalyzed Wacker-type oxidation system using bench-stable K₂S₂O₈ as the oxidant and ethanol as a green solvent. A novel bidentate ligand, 1-(6-phenylpyridin-2-yl)-1H-indazole (L13), leverages electronic asymmetry to form a stable C–Pd–N binding palladium complex (PdL13OAc). Reaction optimization demonstrated exceptional efficiency at low Pd(OAc)₂ loadings (1 mol%), affording 97% yield while enhancing atom economy. Control experiments and ¹⁸O-isotope labeling unequivocally identified H₂O as the oxygen source in the carbonyl products. This work establishes a new bidentate ligand system for Wacker-type oxidations, offering a practical, scalable protocol with record-low catalyst loading that expands synthetic access to carbonyl compounds.