text: Ketones and imines are related functional groups, and effective technologies for the asymmetric hydrogenation of each are also closely related. Early examples are Noyori's ruthenium-chiral diphosphine-diamine system.
  For carbonyl and imine substrates, end-on, η coordination can compete with η mode. For η-bound substrates, the hydrogen-accepting carbon is removed from the catalyst and resists hydrogenation.
  Iridium/P,N ligand-based systems have been effective for some ketones and imines.  For example, a consistent system for benzylic aryl imines uses the P,N ligand SIPHOX in conjunction with iridium(I) in a cationic complex to achieve asymmetric hydrogenation with ee >90%. An efficient catalyst for ketones, (turnover number (TON) up to 4,550,000 and ee up to 99.9%) is an iridium(I) system with a closely related tridentate ligand.
  <br />
  The BINAP/diamine-Ru catalyst is effective for the asymmetric reduction of both functionalized and simple ketones, and BINAP/diamine-Ru catalyst can catalyze aromatic, heteroaromatic, and olefinic ketones enantioselectively. Better stereoselectivity is achieved when one substituent is larger than the other (see Flippin-Lodge angle).