Ytterbium Triflate Catalyzed Heterocyclization of 1,2‐Phenylenediamines and Alkyl Oxalates Under Solvent‐Free Conditions via Phillips Reaction: A Facile Synthesis of Quinoxaline‐2,3‐diones Derivatives

Ytterbium triflate are found to catalyze efficiently the Phillips‐type heterocyclization reactions of 1,2‐phenylenediamine and alkyl oxalate under solvent‐free and mild conditions to afford the corresponding quinoxaline‐2,3‐dione derivatives in high yields. The catalyst could be recovered almost quantitatively from the aqueous layer after the reaction was completed and it could be reused in subsequent reaction without decrease in activity.