Asymmetric Hydrogenation Of Simple Ketones Research Articles

Ru(η1-BH4)(daipena)(diphosphine): Ruthenabicyclic borohydride complexes for asymmetric hydrogenation of ketones and asymmetric formal hydroamination of allylic alcohols under base-free conditions

Ruthenabicyclic complexes bearing a η1-BH4 ligand and exhibiting notable stability under air were developed. These novel Ru complexes were efficient catalyst precursors for asymmetric hydrogenation of simple ketones under base-free conditions or with a small amount of DABCO to afford the corresponding alcohols with high enantioselectivity (>99 % ee in the best cases). Asymmetric formal hydroamination of allylic alcohols without an addition of base, via a borrowing hydrogenation strategy, was also achieved. A variety of allylic alcohols and amines were applicable to the reaction (>99 % ee in the best cases).

Synthesis of Tridentate PNO Ligands with Planar Chirality and Application in Iridium-Catalyzed Asymmetric Hydrogenation of Simple Ketones.

A series of [2,2]paracyclophane-based tridentate PNO ligands with planar chirality were designed and synthesized. The easily prepared chiral tridentate PNO ligands were successfully applied to the iridium-catalyzed asymmetric hydrogenation of simple ketones, giving chiral alcohols with high efficiency and excellent enantioselectivities (up to 99% yield and >99% ee). Control experiments revealed the indispensability of both N-H and O-H in the ligands.

P-chirogenic Trost ligands mediated asymmetric hydrogenation of simple ketones

Herein, we report a highly active catalyst system consisting of (Rc,Rc,Rp,Rp)-P-chirogenic Trost ligand and [Ru(C6H6)Cl2]2 for asymmetric hydrogenation of simple ketones, affording the corresponding optically active alcohols in moderate enantioselectivity. A synergetic effect between P- and C-chirogenic centers of the P-chirogenic Trost ligands was observed in this asymmetric hydrogenation process.

Manganese-Catalyzed Enantioselective Hydrogenation of Simple Ketones Using an Imidazole-Based Chiral PNN Tridentate Ligand

A series of Mn(I) catalysts containing imidazole-based chiral PNN tridentate ligands with controllable ‘side arm’ groups have been established, enabling the inexpensive base-promoted asymmetric hydrogenation of simple ketones with outstanding activities (up to 8200 TON) and good enantioselectivities (up to 88.5% ee). This protocol features wide substrate scope and functional group tolerance, thereby providing easy access to a key intermediate of crizotinib.

A Ferrocene-Based NH-Free Phosphine-Oxazoline Ligand for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones.

A new type of ferrocene-based phosphine-oxazoline ligand has been prepared over a few simple steps. An iridium complex of this ligand is air stable and exhibits excellent performance for the asymmetric hydrogenation of simple ketones (up to 98% yield, up to 99% ee, and 20 000 S/C). Exo-α,β-unsaturated cyclic ketones could be regiospecifically hydrogenated to give chiral allylic alcohols with good results. This study indicates that P,N-ligands can also efficiently promote Ir-catalyzed asymmetric hydrogenation without NH-hydrogen-bonding assistance.

Ir-catalyzed asymmetric hydrogenation of simple ketones with chiral ferrocenyl P,N,N-ligands

The Ir-catalyzed asymmetric hydrogenation of simple aromatic ketones with chiral ferrocenyl P,N,N-ligands has been developed. Under the optimized conditions, a wide range of ketones were hydrogenated to afford the corresponding chiral alcohols in good to excellent enantioselectivities (up to 98% ee).

Iridium-Catalyzed Asymmetric Hydrogenation of Simple Ketones

Iridium-Catalyzed Asymmetric Hydrogenation of Simple Ketones

Iridium Catalysts with f-Amphox Ligands: Asymmetric Hydrogenation of Simple Ketones

A series of modular and rich electronic tridentate ferrocene aminophosphoxazoline ligands (f-amphox) have been successfully developed and used in iridium-catalytic asymmetric hydrogenation of simple ketones to afford corresponding enantiomerically enriched alcohols under mild conditions with superb activities and excellent enantioselectivities (up to 1 000 000 TON, almost all products up to >99% ee, full conversion). The resulting chiral alcohols and their derivatives are important intermediates in pharmaceuticals.

Phosphine-free chiral iridium catalysts for asymmetric catalytic hydrogenation of simple ketones

Phosphine free iridium catalysts with simple structures show efficient enantioselectivities and activities in the asymmetric hydrogenation of simple ketones by using chiral iridium catalysts to chiral alcohols with up to 96% ee.

Stereoselectivity in Asymmetric Catalysis: The Case of Ruthenium-Catalyzed Ketone Hydrogenation.

The ruthenium-catalyzed asymmetric hydrogenation of simple ketones to generate enantiopure alcohols is an important process widely used in the fine chemical, pharmaceutical, fragrance, and flavor industries. Chiral diphosphine-RuCl2-1,2-diamine complexes are effective catalysts for the reaction giving high chemo- and enantioselectivity. However, no diphosphine-RuCl2-1,2-diamine complex has yet been discovered that is universal for all kinds of ketone substrates, and the ligands must be carefully chosen for each substrate. The procedure of finding the best ligands for a specific substrate can be facilitated by using virtual screening as a complement to the traditional experimental screening of catalyst libraries. We have generated a transition state force field (TSFF) for the ruthenium-catalyzed asymmetric hydrogenation of simple ketones using an improved Q2MM method. The developed TSFF can predict the enantioselectivity for 13 catalytic systems taken from the literature, with a mean unsigned error of 2.7 kJ/mol.

Efficient Ru(II)-catalyzed asymmetric hydrogenation of simple ketones with C2-symmetric planar chiral metallocenyl phosphinooxazoline ligands

C2-symmetric metallocenyl planar phosphinooxazoline ligands (2 and 3) have been applied in the Ru(II)-catalyzed asymmetric hydrogenation of simple ketones. This type of ligands enjoys the advantages of dual reaction sites as well as larger steric hindrance than their corresponding C1-symmetric counterparts. As a result, almost quantitative conversions and excellent enantioselectivities were obtained for a series of simple ketones. Under the optimal reaction conditions, up to 99.7% ee was obtained in many cases. It was also confirmed that hydrogen rather than reaction solvent i-PrOH is at work in the hydrogenation procedure.

ChemInform Abstract: Palladium‐Catalyzed Asymmetric Hydrogenation of Simple Ketones Activated by Broensted Acids.

AbstractOptimized conditions including a chiral binaphthyl ligand afford benzyl alcohols with up to 88% e.e.

Palladium-catalyzed asymmetric hydrogenation of simple ketones activated by Brønsted acids

Homogeneous Pd(OCOCF3)2/(R)-C4-TunePhos has been successfully applied in the asymmetric hydrogenation of simple ketones activated by catalytic amount of Brønsted acid with up to 88% ee.

Highly Enantioselective Amido Iridium Catalysts for the Hydrogenation of Simple Ketones

New family of cats: Tailormade amido iridium catalysts with simple structures and no P ligands show excellent enantioselectivities and activities in the asymmetric hydrogenation of simple ketones (see scheme; C yellow, N green, O blue, Ir red). These catalysts may thus be the key to ecologically and economically optimized value creation

ChemInform Abstract: Developing a Chiral Toolbox for Asymmetric Catalytic Reactions

During the last several decades, chemists have made major progress in discovering man-made catalysts to perform challenging asymmetric transformations. The research in our group addresses fundamental and practical problems in this field by developing a diverse set of chiral ligands that combine with transition metals to form highly enantioselective catalysts. Families of tridentate ligands have been developed for the enantioselective hydrogenation of unfunctionalized substrates. In addition, we have developed several new bidentate phosphine ligands for asymmetric catalysis. The common feature of these ligands are that they contain rigid aromatic backbones or ring structures which restrict conformational flexibility of the ligands. Several asymmetric reactions have been studied: asymmetric hydrogenation of functionalized substrates such as N-acylaminoacrylic acids, enamides and enol acetates; asymmetric hydrogenation of simple ketones, and imines; and asymmetric carbon-carbon bond forming reactions. In addition, we have designed and synthesized several novel chiral monophosphines for asymmetric catalytic reactions. Transition metal complexes with these monophosphines have also been developed for asymmetric transformations.

Mechanism of Asymmetric Hydrogenation of Acetophenone Catalyzed by Chiral η6‐Arene–N‐Tosylethylenediamine–Ruthenium(II) Complexes

Chiral arene-N-tosylethylenediamine-Ru(II) complexes can be made to effect both asymmetric transfer hydrogenation and asymmetric hydrogenation of simple ketones through a slight functional modification and by switching reaction conditions. [Ru(OSO2CF3){(S,S)-TsNCH(C6H5)CH(C6H5)NH2}(eta(6)-p-cymene)] catalyzes the asymmetric hydrogenation of acetophenone in methanol to afford (S)-1-phenylethanol with 96% ee in 100% yield. Like the transfer hydrogenation catalyzed by similar Ru catalysts with basic 2-propanol or a formic acid/triethylamine mixture, this hydrogenation proceeds through a metal-ligand bifunctional mechanism. The reduction of the C=O function occurs via an intermediary 18e RuH species in its outer coordination sphere without metal-substrate interaction. The high catalytic efficiency relies on the facile ionization of the Ru triflate complex in methanol. The turnover rate is dependent on hydrogen pressure and medium acidity and basicity. The RuCl analogue can be used as a precatalyst, albeit less effectively. Unlike the well-known diphosphine-1,2-diamine-Ru(II)-catalyzed hydrogenation that proceeds in a basic alcohol, this reaction takes place under slightly acidic conditions, creating new opportunities for asymmetric hydrogenation.

The Hydrogenation/Transfer Hydrogenation Network: Asymmetric Hydrogenation of Ketones with Chiral η6-Arene/N-Tosylethylenediamine−Ruthenium(II) Catalysts

Chiral eta6-arene/N-tosylethylenediamine-Ru(II) complexes, known as excellent catalysts for asymmetric transfer hydrogenation of aromatic ketones in basic 2-propanol, can be used for asymmetric hydrogenation using H2 gas. Active catalysts are generated from RuCl[(S,S)-TsNCH(C6H5)CH(C6H5)NH2](eta6-p-cymene) in methanol, but not 2-propanol, or by combination of Ru[(S,S)-TsNCH(C6H5)CH(C6H5)NH](eta6-p-cymene) and CF3SO3H or other non-nucleophilic acids. This method allows, for the first time, asymmetric hydrogenation of simple ketones under acidic conditions. Hydrogenation of base-sensitive 4-chromanone and its derivatives with the S,S catalyst proceeds in methanol with a substrate-to-catalyst molar ratio of 1000-3000 (10 atm) to 7000 (100 atm), giving (S)-4-chromanols with 97% ee quantitatively. The reaction can be achieved even on a 2.4 kg scale. The mechanistic rationale for the catalytic efficiency is presented.

Asymmetric Hydrogenation of Ketones Catalyzed by Ruthenium Hydride Complexes of a Beta-aminophosphine Ligand Derived from Norephedrine

A series ruthenium complexes with the chiral P−N ligand (1R,2R)-PPh2CHPhCHMeNH2 derived from (1S,2R)-norephedrine are synthesized starting from the complexes RuHCl(PPh3)3 or RuHCl(P−P)(PPh3) (P−P= (R)-binap or (S)-binap). These are precatalysts for the efficient asymmetric hydrogenation of simple ketones. For the hydrogenation of acetophenone to 1-phenylethanol, the enantioselectivity observed can be related to the structure of the precatalysts determined by X-ray diffraction. This relationship breaks down for the hydrogenation of pinacolone.

Trans-RuH(η-BH4)(binap)(1,2-diamine): A Catalyst for Asymmetric Hydrogenation of Simple Ketones under Base-Free Conditions

Reaction of a chiral RuCl2(diphosphine)(1,2-diamine) complex and NaBH4 forms trans-RuH(eta1-BH4)(diphosphine)(1,2-diamine) quantitatively. The TolBINAP/DPEN Ru complex has been characterized by single crystal X-ray analysis as well as NMR and IR spectra. The new Ru complexes allow for asymmetric hydrogenation of simple ketones in 2-propanol without an additional strong base. Various base-sensitive ketones are convertible to chiral alcohols in a high enantiomeric purity with a substrate/catalyst ratio of up to 100 000 under mild conditions. Configurationally unstable 2-isopropyl- and 2-methoxycyclohexanone can be kinetically resolved with a high enantiomer discrimination. This procedure overcomes the drawback of an earlier method using RuCl2(diphosphine)(diamine) and an alkaline base, which sometimes causes undesired reactions such as ester exchange, epoxy-ring opening, beta-elimination, and polymerization of ketonic substrates.

単純ケトン類の高速かつ高立体選択的水素化反応

Hydrogenation of ketones is amongst one of the most important synthetic reactions. This transformation is not only of academic interest, but also of industrial significance because of its simplicity, environmentally friendliness, and economic viability. trans-RuCl2 (phosphine) 2 (1, 2-diamine), when coupled with a strong base in 2-propanol, acts- as the most reactive catalyst for homogeneous hydrogenation of ketones. This reaction, unlike conventional hydrogenation, proceeds selectively at a C=O bond leaving coexisting C=C linkages intact. Furthermore, rapid, highly productive asymmetric hydrogenation of simple ketones has been realized by using trans-RuCl2 [(S) -tolbinap] [(S, S) -dpen] or its optical antipode. When acetophenone is hydrogenated with the complex, the turnover number reaches 2, 400, 000 and the turnover frequency as high as 228, 000 h-1 or 63 s-1. When XylBINAP is used as a chiral phosphine, a wide variety of prochiral ketones are hydrogenated in up to 100% ee. This practical asymmetric hydrogenation will greatly facilitate the synthesis of biologically active compounds and functional materials.