Asymmetric Hydrogenation of 2,4‐Disubstituted 1,5‐Benzodiazepines Using Cationic Ruthenium Diamine Catalysts: An Unusual Achiral Counteranion Induced Reversal of Enantioselectivity

BArFing it out the other way: A highly enantioselective hydrogenation of 2,4-disubstituted 1,5-benzodiazepines using chiral cationic ruthenium diamine catalysts (R,R)-1 has been developed (see scheme; BArF=tetrakis(3,5-bistrifluoromethylphenyl)borate). Either enantiomer of 2,4-diaryl-2,3,4,5-tetrahydro-1H-benzodiazepine derivatives could be obtained by using the same enantiomer of ligand but in the presence of a different achiral counteranion.