Novel chiral tetraaza ligands: synthesis and application in asymmetric transfer hydrogenation of ketones

Novel chiral tetraaza ligands, N¹,N²-bis(2-(piperidin-1-yl)benzylidene)cyclohexane-1,2-diamine 1 and N¹,N²-bis(2-(piperidin-1-yl)benzyl)cyclohexane-1,2-diamine 2, have been synthesized and fully characterized by analytical and spectroscopic methods. The structure of (R,R)-1 has been established by X-ray crystallography. Asymmetric transfer hydrogenation of aromatic ketones with the catalysts prepared in situ from [IrHCl₂(COD)]₂ and the chiral tetraaza ligands in 2-propanol gave the corresponding optically active secondary alcohols in high conversions and good ees (up to 91%) under mild reaction conditions.