Asymmetric hydrogenation of aromatic ketones using an iridium(I) catalyst containing ferrocene-based P–N–N tridentate ligands

Six ferrocene-based P–N–N tridentate ligands have been synthesized and applied in the Ir-catalyzed asymmetric hydrogenation of aromatic ketones. A wide range of ketones are hydrogenated enantioselectively to afford the corresponding optically active alcohols in the enantioselectivities of up to 86.6% ee. The substituent groups on the P-phenyl and pyridine rings play an important role with regard to the enantioselectivity.

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(RC,SFc)-1-(Diphenylphosphino)-2-[1-N-(pyridin-2-ylmethyl)ethyl]ferroceneC30H29FeN2P[α]D25=-320.2 (c 0.25, CH2Cl2)Absolute configuration: (RC,SFc)

(RC,SFc)-1-(Diphenylphosphino)-2-[1-N-(3-methylpyridin-2-yl methyl)ethyl]ferroceneC31H31FeN2P[α]D25=-353.6 (c 0.25, CH2Cl2)Absolute configuration: (RC,SFc)

(RC,SFc)-1-(Diphenylphosphino)-2-[1-N-(quinolin-2-ylmethyl)ethyl]ferroceneC34H31FeN2P[α]D25=-276.8 (c 0.25, CH2Cl2)Absolute configuration: (RC,SFc)

(RC,SFc)-1-(Diphenylphosphino)-2-[1-N-(6-methylpyridin-2-yl methyl)ethyl]ferroceneC31H31FeN2P[α]D25=-243.8 (c 0.65, CH2Cl2)Absolute configuration: (RC,SFc)

(RC,SFc)-1-[Bis(3,5-dimethylphenyl)phosphino]-2-[1-N-(6-methylpyridin-2-ylmethyl)ethyl]ferroceneC35H39FeN2P[α]D25=-262.4 (c 0.25, CH2Cl2)Absolute configuration: (RC,SFc)

(RC,SFc)-1-[Bis(3,5-di-tert-butylphenyl)phosphino]-2-[1-(dim-ethylamino)ethyl]ferroceneC42H60FeNP[α]D25=-246.8 (c 0.25, CH2Cl2)Absolute configuration: (RC,SFc)

(RC,SFc)-1-[Bis(3,5-di-tert-butylphenyl)phosphino]-2-[(1-amino)ethyl]ferroceneC40H56FeNP[α]D25=-205.6 (c 0.25, CHCl3)Absolute configuration: (RC,SFc)

(RC,SFc)-1-[Bis(3,5-di-tert-butylphenyl)phosphino]-2-[1-N-(6-methylpyridin-2-ylmethyl)ethyl] ferroceneC47H63FeN2P[α]D25=-184.6 (c 0.25, CH2Cl2)Absolute configuration: (RC,SFc)