Highly enantioselective Ru-catalyzed hydrogenation of β-keto esters using electron-donating bis(trialkylphosphine) ligand-TangPhos

Highly electron-donating bis(trialkylphosphine) TangPhos and its corresponding ruthenium complexes provided high enantioselectivities for the hydrogenation of β-keto esters. Up to 99.8% and 99.5% ee have been achieved in hydrogenation of β-alkyl and β-aryl substituted β-keto esters, respectively. Asymmetric hydrogenation of ethyl 4-chloro acetoacetate in 98.2% ee is also reported.