ruthenocene-based phosphine-oxazoline ligand tBu-mono-RuPHOX or the diphosphine ligand BINAP, were developed for the asymmetrichydrogenation of 5,6-dihydropyrazin-2(1H)-ones, affording chiral piperazin-2-ones in good yields and with moderate to good ees. Different catalytic behaviors for the hydrogenation of these types of substrate were observed with these two catalyst systems. Our tBu-mono-RuPHOX ligand, which