Iridium complex bearing a chiral hydroxy-amide functionalized N-heterocyclic carbene: a catalyst precursor for asymmetric transfer hydrogenation

A pyrazole co-ligand permits a low loading iridium-catalyzed asymmetric transfer hydrogenation which is proposed to proceed through metal–ligand cooperativity.

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Asymmetric Transfer Hydrogenation of Nitroalkenes by an Iridium Complex

Synfacts ◽

10.1055/s-0033-1339786 ◽

2013 ◽

Vol 9 (10) ◽

pp. 1079-1079

Keyword(s):

Transfer Hydrogenation ◽

Iridium Complex ◽

Asymmetric Transfer Hydrogenation

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Arene‐Immobilized Ru(II)/TsDPEN Complexes: Synthesis and Applications to the Asymmetric Transfer Hydrogenation of Ketones

European Journal of Inorganic Chemistry ◽

10.1002/ejic.202000948 ◽

2020 ◽

Author(s):

Simon Doherty ◽

Julian G. Knight ◽

Hind Alshaikh ◽

James Wilson ◽

Paul G. Waddell ◽

...

Keyword(s):

Transfer Hydrogenation ◽

Asymmetric Transfer Hydrogenation

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New Bifunctional Bis(azairidacycle) with Axial Chirality via Double Cyclometalation of 2,2′-Bis(aminomethyl)-1,1′-binaphthyl

Molecules ◽

10.3390/molecules26041165 ◽

2021 ◽

Vol 26 (4) ◽

pp. 1165

Author(s):

Yasuhiro Sato ◽

Yuichi Kawata ◽

Shungo Yasui ◽

Yoshihito Kayaki ◽

Takao Ikariya

Keyword(s):

Hydrogen Transfer ◽

Bond Cleavage ◽

Enantiomeric Excess ◽

Transfer Hydrogenation ◽

Catalyst Precursor ◽

Asymmetric Catalysts ◽

Axially Chiral ◽

Diastereomeric Mixture ◽

Raney Ni ◽

Half Sandwich

As a candidate for bifunctional asymmetric catalysts containing a half-sandwich C–N chelating Ir(III) framework (azairidacycle), a dinuclear Ir complex with an axially chiral linkage is newly designed. An expedient synthesis of chiral 2,2′-bis(aminomethyl)-1,1′-binaphthyl (1) from 1,1-bi-2-naphthol (BINOL) was accomplished by a three-step process involving nickel-catalyzed cyanation and subsequent reduction with Raney-Ni and KBH4. The reaction of (S)-1 with an equimolar amount of [IrCl2Cp*]2 (Cp* = η5–C5(CH3)5) in the presence of sodium acetate in acetonitrile at 80 °C gave a diastereomeric mixture of new dinuclear dichloridodiiridium complexes (5) through the double C–H bond cleavage, as confirmed by 1H NMR spectroscopy. A loss of the central chirality on the Ir centers of 5 was demonstrated by treatment with KOC(CH3)3 to generate the corresponding 16e amidoiridium complex 6. The following hydrogen transfer from 2-propanol to 6 provided diastereomers of hydrido(amine)iridium retaining the bis(azairidacycle) architecture. The dinuclear chlorido(amine)iridium 5 can serve as a catalyst precursor for the asymmetric transfer hydrogenation of acetophenone with a substrate to a catalyst ratio of 200 in the presence of KOC(CH3)3 in 2-propanol, leading to (S)-1-phenylethanol with up to an enantiomeric excess (ee) of 67%.

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Design of Iridium N-Heterocyclic Carbene Amino Acid Catalysts for Asymmetric Transfer Hydrogenation of Aryl Ketones

Catalysts ◽

10.3390/catal11060671 ◽

2021 ◽

Vol 11 (6) ◽

pp. 671

Author(s):

Chad M. Bernier ◽

Joseph S. Merola

Keyword(s):

Amino Acids ◽

Amino Acid ◽

Enantiomeric Excess ◽

Transfer Hydrogenation ◽

Acid Catalysts ◽

Asymmetric Transfer Hydrogenation ◽

Reaction Conditions ◽

Chiral Complexes ◽

Acetophenone Derivatives ◽

Aryl Ketones

A series of chiral complexes of the form Ir(NHC)2(aa)(H)(X) (NHC = N-heterocyclic carbene, aa = chelated amino acid, X = halide) was synthesized by oxidative addition of -amino acids to iridium(I) bis-NHC compounds and screened for asymmetric transfer hydrogenation of ketones. Following optimization of the reaction conditions, NHC, and amino acid ligands, high enantioselectivity was achieved when employing the Ir(IMe)2(l-Pro)(H)(I) catalyst (IMe = 1,3-dimethylimidazol-2-ylidene), which asymmetrically reduces a range of acetophenone derivatives in up to 95% enantiomeric excess.

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