Rate Enhancement in CAN-Promoted Pd(PPh₃)₂Cl₂‑Catalyzed Oxidative Cyclization: Synthesis of 2‑Ketofuran-4-carboxylate Esters

Stoichiometric ceric ammonium nitrate (CAN) and a catalytic amount of Pd­(PPh₃)₂Cl₂ (5 mol %) can rapidly produce multisubstituted 2-ketofuran-4-carboxylate esters from 2-propargylic 1,3-ketoesters via oxidative O-cyclization reaction. Pd­(PPh₃)₂Cl₂ was found to be the crucial catalyst as its inclusion greatly enhanced the rate of the reaction and cleanly afforded the products within minutes. Over 30 substrates were successfully converted to the desired compounds in mostly moderate to good yields.