Ruthenium and Iridium Dipyridylamine Catalysts for the Efficient Synthesis of γ-Valerolactone by Transfer Hydrogenation of Levulinic Acid

Abstract

The selective and efficient transfer hydrogenation of levulinic acid into γ-valerolactone was performed with new ruthenium and iridium catalysts bearing dipyridylamine (dpa) ligands. Reactions were performed in the presence of formic acid and triethylamine using catalyst loading as low as 0.05 mol % with a ruthenium complex (turnover number = 1980). Recyclability of a ruthenium catalyst was demonstrated by running 6 consecutive reactions in almost quantitative yields.