cas 27948-61-4, (R)-(+)-1-(2-FURYL)ETHANOL

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A common synthetic route to homochiral tetracycles related to pillaromycinone and premithramycinone
Homochiral AB segments for (+)-and (-)-pillaromycinone were prepared in 11 steps from 2-acetylfuran. The synthesis featured an intramolecular Diels-Alder reaction of a 2,5-disubstituted furan and a hydroxyl-directed homogeneous hydrogenation of the tetrasubstituted alkene double bond of two enones. The CD segment was attached by a modified Staunton-Weinreb annulation to produce the desired homochiral tetracycle 21c related to (+)-pillaromycinone. An unusual acetonide migration enabled the synthesis of a tetracyclic model for premithramycinone.
Hill, Bryan,Jordan, Robert,Qu, Yang,Assoud, Abdeljalil,Rodrigo, Russell
p. 1457 - 1468
(2011)
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Biomimetic Synthesis of Rhytidenone A and Mode of Action of Cytotoxic Rhytidenone F
The rhytidenone family comprises spirobisnaphthalene natural products isolated from the mangrove endophytic fungus Rhytidhysteron rufulum AS21B. The biomimetic synthesis of rhytidenone A was achieved by a Michael reaction/aldol/lactonization cascade in a single step from the proposed biosynthetic precursor rhytidenone F. Moreover, the mode of action of the highly cytotoxic rhytidenone F was investigated. The pulldown assay coupled with mass spectrometry analysis revealed the target protein PA28γ is covalently attached to rhytidenone F at the Cys92 residue. The interactions of rhytidenone F with PA28γ lead to the accumulation of p53, which is an essential tumor suppressor in humans. Consequently, the Fas-dependent signaling pathway is activated to initiate cellular apoptosis. These studies have identified the first small-molecule inhibitor targeting PA28γ, suggesting rhytidenone F may serve as a promising natural product lead for future anticancer drug development.
Chen, Kaiqi,Lam, Hiu C.,Lei, Xiaoguang,Liu, Yaxi,Pudhom, Khanitha,Siridechakorn, Ittipon,Yue, Zongwei
p. 4115 - 4120
(2020)
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Cinchona-Alkaloid-Derived NNP Ligand for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones
Most ligands applied for asymmetric hydrogenation are synthesized via multistep reactions with expensive chemical reagents. Herein, a series of novel and easily accessed cinchona-alkaloid-based NNP ligands have been developed in two steps. By combining [Ir(COD)Cl]2, 39 ketones including aromatic, heteroaryl, and alkyl ketones have been hydrogenated, all affording valuable chiral alcohols with 96.0-99.9% ee. A plausible reaction mechanism was discussed by NMR, HRMS, and DFT, and an activating model involving trihydride was verified.
Zhang, Lin,Zhang, Ling,Chen, Qian,Li, Linlin,Jiang, Jian,Sun, Hao,Zhao, Chong,Yang, Yuanyong,Li, Chun
supporting information
p. 415 - 419
(2022/01/12)

2, 4, 5-Trideoxyhexopyranosides Derivatives of 4’-Demethylepipodophyllotoxin: De novo Synthesis and Anticancer Activity
Background: Podophyllotoxin is a natural lignan which possesses anticancer and antiviral activities. Etoposide and teniposide are semisynthetic glycoside derivatives of podophyllotoxin and are increasingly used in cancer medicine. Objective: The present work aimed to design and synthesize a series of 2, 4, 5-trideoxyhexopyrano-sides derivatives of 4’-demethylepipodophyllotoxin as novel anticancer agents. Methods: A divergent de novo synthesis of 2, 4, 5-trideoxyhexopyranosides derivatives of 4’-demethylepipodophyllotoxin has been established via palladium-catalyzed glycosylation. The abili-ties of synthesized glycosides to inhibit the growth of A549, HepG2, SH-SY5Y, KB/VCR and HeLa cancer cells were investigated by MTT assay. Flow cytometric analysis of cell cycle with propidium iodide DNA staining was employed to observe the effect of compound 5b on cancer cell cycle. Results: Twelve D and L monosaccharide derivatives 5a-5l have been efficiently synthesized in three steps from various pyranone building blocks employing de novo glycosylation strategy. D-monosaccharide 5b showed the highest cytotoxicity on five cancer cell lines with the IC50 values ranging from 0.9 to 6.7 μM. It caused HepG2 cycle arrest at G2/M phase in a concentration-dependent manner. Conclusion: The present work leads to the development of novel 2, 4, 5-trideoxyhexopyranosides derivatives of 4’-demethylepipodophyllotoxin. The biological results suggest that the replacement of the glucosyl moiety of etoposide with 2, 4, 5-trideoxyhexopyranosyl is favorable to their cytotoxic-ity. D-monosaccharide 5b was observed to cause HepG2 cycle arrest at the G2/M phase in a concen-tration-dependent manner.
Cai, Rui,Li, Yu,Lu, Yapeng,Zhao, Yu,Zhu, Li
p. 130 - 139
(2022/03/09)

Practical access to (S)-heterocyclic aromatic acetates via CAL-B/Na2CO3-deacylation and Mitsunobu reaction protocol
Herein, we report the preparation of enantiomerically pure forms of 2,3-dihydrobenzofuran-3-ol (1), chroman-4-ol (2), thiochroman-4-ol (3), 1-(furan-2-yl) ethanol (5) and 1-(thiophen-2-yl) ethanol (6), through a kinetic resolution catalysed by Candida antarctica lipase B/Na2CO3 hydrolysis sequence in organic media. The (R)-furnished alcohols and the (S)-remained acetates are recovered enantiopures (ee?>99%, E???200, Conv = 50%). Those ideal enzymatic kinetic resolution (EKRs) are well incorporated to the Mitsunobu inversion protocol in a one pot procedure to give (S)-heterocyclic acetates (1a–3a) in good to high enantiomeric excess (88%–92% ee). Whilst, the (S)-heteroaromatic acetates (5a and 6a) are given with moderate enantiomeric excess (51%–62% ee). All the (S)-acetates are given in good isolated chemical yields (>80%) allowing to overcome the maximum of 50% yield which could be usually reached in a regular kinetic resolution processes.
Aribi-Zouioueche, Louisa,Bra?a, Nabila,Merabet-Khelassi, Mounia,Toffano, Martial
(2022/02/11)

Palladium-Catalyzed Regioselective and Diastereoselective C-Glycosylation by Allyl-Allyl Coupling
A Pd-catalyzed C-glycosylation reaction was developed by allyl-allyl coupling process using Achmatowicz rearrangement products as donors and methylcoumarins as acceptors under mild conditions. This method featured regio- and diastereoselectivities, stereo
Li, Junhao,Zheng, Nan,Duan, Xuelun,Li, Rui,Song, Wangze
supporting information
p. 846 - 850
(2020/12/13)

Asymmetric reduction of aromatic heterocyclic ketones with bio-based catalyst Lactobacillus kefiri P2
Abstract: Chiral heterocyclic secondary alcohols have received much attention due to their widespread use in pharmaceutical intermediates. In this study, Lactobacillus kefiri P2 biocatalysts isolated from traditional dairy products, were used to catalyze the asymmetric reduction of prochiral ketones to chiral secondary alcohols. Secondary chiral carbinols were obtained by asymmetric bioreduction of different prochiral substrates with results up to > 99% enantiomeric excess (ee). (R)-1-(benzofuran-2-yl)ethanol 5a, which can be used in the synthesis of pharmaceuticals such as bufuralols potent nonselective β-blockers antagonists, Amiodarone (cardiac anti-arrhythmic), and Benziodarone (coronary vasodilator), was produced in gram-scale, high yield and enantiomerically pure form using L. kefiri P2 biocatalysts. The gram-scale production was carried out, and 9.70?g of (R)-5a in enantiomerically pure form was obtained in 96% yield. Also, production of (R)-5a in terms of yield and gram scale through catalytic asymmetric reduction using the biocatalyst was the highest report so far. This is a cost-effective, clean and eco-friendly process for the preparation of chiral secondary alcohols compared to chemical processes. From an environmental and economic perspective, this biocatalytic method has great application potential, making it a green and sustainable way of synthesis. Graphical Abstract: [Figure not available: see fulltext.]
Bayda?, Yasemin,Kalay, Erbay,?ahin, Engin
p. 1147 - 1155
(2020/10/06)

Asymmetric reduction of prochiral aromatic and hetero aromatic ketones using whole-cell of Lactobacillus senmaizukei biocatalyst
Asymmetric bioreduction of aromatic and heteroaromatic ketones is an important process in the production of precursors of biologically active molecules. In this study, the bioreduction of aromatic and hetero aromatic prochiral ketones into optically active alcohols was investigated using Lactobacillus senmaizukei as a whole-cell catalyst, since whole-cells are less expensive than pure enzymes. The study indicates enantioselective bioreduction of various substituted aromatic ketones (1–16) to the corresponding (R)-and (S)-chiral secondary alcohols (1a–16a) in low to excellent enantioselectivity (6–94%) with good yields (58–95%). In addition, heteroaromatic prochiral ketones 1-(pyridin-2-yl)ethanone (17) and 1-(furan-2-yl)ethanone (18) were reduced to (R)-17a and (R)-18a in enantiopure form with excellent conversion (>99%) and yields. These findings show that L. senmaizukei is a very important biocatalyst for asymmetric reduction of both 6-membered and 5-member heteroaromatic methyl ketones. This method promising a green synthesis for the synthesis of biologically important secondary chiral alcohols in an environmentally friendly and inexpensive process.
?olak, Nida Sezin,Kalay, Erbay,?ahin, Engin
p. 2305 - 2315
(2021/05/31)

Highly Active Cooperative Lewis Acid—Ammonium Salt Catalyst for the Enantioselective Hydroboration of Ketones
Enantiopure secondary alcohols are fundamental high-value synthetic building blocks. One of the most attractive ways to get access to this compound class is the catalytic hydroboration. We describe a new concept for this reaction type that allowed for exceptional catalytic turnover numbers (up to 15 400), which were increased by around 1.5–3 orders of magnitude compared to the most active catalysts previously reported. In our concept an aprotic ammonium halide moiety cooperates with an oxophilic Lewis acid within the same catalyst molecule. Control experiments reveal that both catalytic centers are essential for the observed activity. Kinetic, spectroscopic and computational studies show that the hydride transfer is rate limiting and proceeds via a concerted mechanism, in which hydride at Boron is continuously displaced by iodide, reminiscent to an SN2 reaction. The catalyst, which is accessible in high yields in few steps, was found to be stable during catalysis, readily recyclable and could be reused 10 times still efficiently working.
Titze, Marvin,Heitk?mper, Juliane,Junge, Thorsten,K?stner, Johannes,Peters, René
supporting information
p. 5544 - 5553
(2021/02/05)

Ruthenium-catalyzed hydrogenation of aromatic ketones using chiral diamine and monodentate achiral phosphine ligands
The Ru-catalyzed asymmetric hydrogenation of ketones with chiral diamine and monodentate achiral phosphine has been developed. A wide range of ketones were hydrogenated to afford the corresponding chiral secondary alcohols in good to excellent enantioselectivities (up to 98.1% ee). In addition, an appropriate mechanism for the asymmetric hydrogenation was proposed and verified by NMR spectroscopy.
Wang, Mengna,Zhang, Ling,Sun, Hao,Chen, Qian,Jiang, Jian,Li, Linlin,Zhang, Lin,Li, Li,Li, Chun
(2021/03/24)

Dynamic Kinetic Resolution of Alcohols by Enantioselective Silylation Enabled by Two Orthogonal Transition-Metal Catalysts
A nonenzymatic dynamic kinetic resolution of acyclic and cyclic benzylic alcohols is reported. The approach merges rapid transition-metal-catalyzed alcohol racemization and enantioselective Cu-H-catalyzed dehydrogenative Si-O coupling of alcohols and hydrosilanes. The catalytic processes are orthogonal, and the racemization catalyst does not promote any background reactions such as the racemization of the silyl ether and its unselective formation. Often-used ruthenium half-sandwich complexes are not suitable but a bifunctional ruthenium pincer complex perfectly fulfills this purpose. By this, enantioselective silylation of racemic alcohol mixtures is achieved in high yields and with good levels of enantioselection.
Oestreich, Martin,Seliger, Jan
p. 247 - 251
(2020/10/29)

Phase Separation-Promoted Redox Deracemization of Secondary Alcohols over a Supported Dual Catalysts System
Unification of oxidation and reduction in a one-pot deracemization process has great significance in the preparation of enantioenriched organic molecules. However, the intrinsic mutual deactivation of oxidative and reductive catalysts and the extrinsic incompatible reaction conditions are unavoidable challenges in a single operation. To address these two issues, we develop a supported dual catalysts system to overcome these conflicts from incompatibility to compatibility, resulting in an efficient one-pot redox deracemization of secondary alcohols. During this transformation, the TEMPO species onto the outer surface of silica nanoparticles catalyze the oxidation of racemic alcohols to ketones, and the chiral Rh/diamine species in the nanochannels of the thermoresponsive polymer-coated hollow-shell mesoporous silica enable the asymmetric transfer hydrogenation (ATH) of ketones to chiral alcohols. To demonstrate the general feasibility, a series of orthogonal oxidation/ATH cascade reactions are compared to prove the compatible benefits in the elimination of their deactivations and the balance of the cascade directionality. As presented in this study, this redox deracemization process provides various chiral alcohols with enhanced yields and enantioselectivities relative to those from unsupported dual catalysts systems. Furthermore, the dual catalysts can be recycled continuously, making them an attractive feature in the application.
Zhao, Zhitong,Wang, Chengyi,Chen, Qipeng,Wang, Yu,Xiao, Rui,Tan, Chunxia,Liu, Guohua
p. 4055 - 4063
(2021/08/12)

Arene-Immobilized Ru(II)/TsDPEN Complexes: Synthesis and Applications to the Asymmetric Transfer Hydrogenation of Ketones
The Noyori-Ikariya (arene)Ru(II)/TsDPEN precatalyst has been anchored to amorphous silica and DAVISIL through the η6-coordinated arene ligand via a straightforward synthesis and the derived systems, (arene)Ru(II)/TsDPEN@silica and (arene)Ru(II)/TsDPEN@DAVISIL, form highly efficient catalysts for the asymmetric transfer hydrogenation of a range of electron-rich and electron-poor aromatic ketones, giving good conversion and excellent ee's under mild reaction conditions. Moreover, catalyst generated in situ immediately prior to addition of substrate and hydrogen donor, by reaction of silica-supported [(arene)RuCl2]2 with (S,S)-TsDPEN, was as efficient as that generated from its preformed counterpart [(arene)Ru{(S,S)-TsDPEN}Cl]@silica. Gratifyingly, the initial TOFs (up to 1085 h?1) and ee's (96–97 %) obtained with these catalysts either rivalled or outperformed those previously reported for catalysts supported by either silica or polymer immobilized through one of the nitrogen atoms of TsDPEN. While the high ee's were also maintained during recycle studies, the conversion dropped steadily over the first three runs due to gradual leaching of the ruthenium.
Doherty, Simon,Knight, Julian G.,Alshaikh, Hind,Wilson, James,Waddell, Paul G.,Wills, Corinne,Dixon, Casey M.
supporting information
p. 226 - 235
(2020/12/31)

Abiotic reduction of ketones with silanes catalysed by carbonic anhydrase through an enzymatic zinc hydride
Enzymatic reactions through mononuclear metal hydrides are unknown in nature, despite the prevalence of such intermediates in the reactions of synthetic transition-metal catalysts. If metalloenzymes could react through abiotic intermediates like these, then the scope of enzyme-catalysed reactions would expand. Here we show that zinc-containing carbonic anhydrase enzymes catalyse hydride transfers from silanes to ketones with high enantioselectivity. We report mechanistic data providing strong evidence that the process involves a mononuclear zinc hydride. This work shows that abiotic silanes can act as reducing equivalents in an enzyme-catalysed process and that monomeric hydrides of electropositive metals, which are typically unstable in protic environments, can be catalytic intermediates in enzymatic processes. Overall, this work bridges a gap between the types of transformation in molecular catalysis and biocatalysis. [Figure not available: see fulltext.]
Ji, Pengfei,Park, Jeeyoung,Gu, Yang,Clark, Douglas S.,Hartwig, John F.
p. 312 - 318
(2021/02/26)

Synthetic Studies toward the Berkeleyacetal Core Architecture
Berkeleyacetals are structurally complex natural products that have shown potent anti-inflammatory activity. The presence of a highly dense oxygen functionality and a polycyclic ring system presents significant synthetic challenges. Herein, we report an e
Márquez-Cadena, Miguel Adrián,Zhang, Wei,Tong, Rongbiao
supporting information
p. 9227 - 9231
(2021/11/30)

RETRACTED ARTICLE: The Manganese(I)-Catalyzed Asymmetric Transfer Hydrogenation of Ketones: Disclosing the Macrocylic Privilege
The bis(carbonyl) manganese(I) complex [Mn(CO)2(1)]Br (2) with a chiral (NH)2P2 macrocyclic ligand (1) catalyzes the asymmetric transfer hydrogenation of polar double bonds with 2-propanol as the hydrogen source. Ketones (43 substrates) are reduced to alcohols in high yields (up to >99 %) and with excellent enantioselectivities (90–99 % ee). A stereochemical model based on attractive CH–π interactions is proposed.
Passera, Alessandro,Mezzetti, Antonio
supporting information
p. 187 - 191
(2019/12/11)

Chiral amino-pyridine-phosphine tridentate ligand, manganese complex, and preparation method and application thereof
The invention discloses a chiral amino-pyridine-phosphine tridentate ligand, a manganese complex, and a preparation method and application thereof. The chiral amino-pyridine-phosphine tridentate ligand is shown as a formula II, and the manganese complex of the chiral amino-pyridine-phosphine tridentate ligand can be used for efficiently catalyzing and hydrogenating ketone compounds to prepare chiral alcohol compounds in a high enantioselectivity mode. The chiral amino-pyridine-phosphine tridentate ligand and the manganese complex are simple in synthesis process, good in stability, high in catalytic activity and mild in reaction conditions.
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Paragraph 0597-0600; 0602

(2020/07/13)

A simple and efficient asymmetric hydrogenation of heteroaromatic ketones with iridium catalyst composed of chiral diamines and achiral phosphines
An efficient iridium catalyst composed of a simple and commercially available o-methoxytriphenylphosphine and 9-Amino (9-deoxy) epi-cinchonine was applied to the asymmetric hydrogenation of heteroaromatic ketones. A range of simple heteroaromatic ketones could be hydrogenated with good to excellent enantioselectivities and high activities. In particular, thiophene ketones and furyl ketones furnished 98.6% ee with up to 2.18 × 104(1/h) TOF. This catalytic system can be of practical value.
Li, Chun,Lu, Xunhua,Wang, Mengna,Zhang, Ling,Jiang, Jian,Yan, Shunfa,Yang, Yuanyong,Zhao, Yonglong,Zhang, Lin
(2020/09/02)

SECONDARY ARYL ALCOHOL AND METHOD OF SYNTHESIZING THEREOF
The present invention relates to secondary aryl alcohol and a method for synthesizing the same and, specifically, to synthesizing secondary aryl alcohol having high optical selectivity through a hydrosilylation reaction using ketone containing an aryl group. In the method for synthesizing secondary aryl alcohol according to an embodiment of the present invention, secondary aryl alcohol is synthesized by making ketone react with hydrosilane under a chiral boron Lewis acid catalyst.COPYRIGHT KIPO 2020
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Paragraph 0032; 0062-0069

(2020/05/13)

Water soluble Ru (II)–p-cymene complexes of chiral aroylthiourea ligands derived from unprotected D/L-alanine as proficient catalysts for asymmetric transfer hydrogenation of ketones
The newfangled chiral aroylthiourea ligands (L1-L6) were produced from unprotected D/L-alanine and their water soluble Ru (II) organometallic catalysts (1–6) were designed from their reaction with [RuCl2(η6-p-cymene)]2. The analytical and spectral methods were used to confirm the structure of the ligands and complexes. The solid state structure of L1, 5 and 6 was confirmed by single crystal XRD. The organometallic compounds (1–6) catalyzed the asymmetric transfer hydrogenation of aromatic, heteroaromatic and bulky ketones to yield respective enantiopure secondary alcohols with admirable conversions (up to 99%) and attractive enantiomeric excesses (ee up to 98%), in presence of formic acid and triethylamine in water medium under non-inert atmospheric conditions.
Sheeba, Mani Mary,Tamizh, Manoharan Muthu,Bhuvanesh, Nattamai S.P.,Karvembu, Ramasamy
(2019/01/04)

Manganese Catalyzed Asymmetric Transfer Hydrogenation of Ketones Using Chiral Oxamide Ligands
The asymmetric transfer hydrogenation of ketones using isopropyl alcohol (IPA) as hydrogen donor in the presence of novel manganese catalysts is explored. The selective and active systems are easily generated in situ from [MnBr(CO)5] and inexpensive C2-symmeric bisoxalamide ligands. Under the optimized reaction conditions, the Mn-derived catalyst gave higher enantioselectivity compared with the related ruthenium catalyst.
Schneek?nig, Jacob,Junge, Kathrin,Beller, Matthias
supporting information
p. 503 - 507
(2019/02/26)

Asymmetric transfer hydrogenation of ketones using Ru(0) nanoparticles modified by Chiral Thiones
The catalytic asymmetric transfer hydrogenation (ATH) of acetophenone in isopropanol by Ru(0) nanoparticles (NPs) obtained by the in-situ reduction of Ru (II) half-sandwich complexes of chiral 2-oxazolidinethiones and 2-thiozolidinethiones was examined and compared with the catalytic activity of Ru(0) NPs formed in-situ by the reduction of [Ru(p-cymene)(Cl)2]2 in presence of optically active ligands such as (S)-4-isobutylthiazolidine-2-thione, (S)-4-Isopropyl-2(?2-pyridinyl)-2-oxazoline, (8S, 9R)-(?)-cinchonidine, (S)-leucinol, (S)-phenylalaninol, and (S)-leucine. Three of the best catalytic systems were then examined for ATH of thirteen aromatic ketones with different electronic and steric properties. A maximum of 24% ee was obtained using NPs generated from the Ru (II) half-sandwich complex with (S)-4-isobutylthiazolidine-2-thione in the TH of acetophenone. The NPs were characterized by TEM and DLS measurements. Kinetic studies and poisoning experiments confirmed that the reaction is catalyzed by the chiral NPs formed in-situ. Complete characterization of the complexes, including the X-ray crystallographic characterization of two complexes, was also carried out.
Din Reshi, Noor U.,Senthurpandi, Dineshchakravarthy,Samuelson, Ashoka G.
(2019/03/21)

Lutidine-Based Chiral Pincer Manganese Catalysts for Enantioselective Hydrogenation of Ketones
A series of MnI complexes containing lutidine-based chiral pincer ligands with modular and tunable structures has been developed. The complex shows unprecedentedly high activities (up to 9800 TON; TON=turnover number), broad substrate scope (81 examples), good functional-group tolerance, and excellent enantioselectivities (85–98 % ee) in the hydrogenation of various ketones. These aspects are rare in earth-abundant metal catalyzed hydrogenations. The utility of the protocol have been demonstrated in the asymmetric synthesis of a variety of key intermediates for chiral drugs. Preliminary mechanistic investigations indicate that an outer-sphere mode of substrate–catalyst interactions probably dominates the catalysis.
Zhang, Linli,Tang, Yitian,Han, Zhaobin,Ding, Kuiling
supporting information
p. 4973 - 4977
(2019/03/17)

Asymmetric Magnesium-Catalyzed Hydroboration by Metal-Ligand Cooperative Catalysis
Asymmetric catalysis with readily available, cheap, and non-toxic alkaline earth metal catalysts represents a sustainable alternative to conventional synthesis methodologies. In this context, we describe the development of a first MgII-catalyzed enantioselective hydroboration providing the products with excellent yields and enantioselectivities. NMR spectroscopy studies and DFT calculations provide insights into the reaction mechanism and the origin of the enantioselectivity which can be explained by a metal-ligand cooperative catalysis pathway involving a non-innocent ligand.
Falconnet, Alban,Magre, Marc,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
supporting information
p. 17567 - 17571
(2019/11/13)

Manganese complex and preparation method and application thereof
The invention discloses a manganese complex taking (RC,SP)-N-5,6,7,8-tetrahydroquinoline-1-(2-diphenylphosphino)ferrocene ethyl amine as a ligand, a preparation method and application of the manganesecomplex in catalyst ketone compound asymmetric hydrogen transfer reduction preparing chiral alcohol. The manganese complex is a cheap metal chiral catalyst, the cost is low, the thermal stability isgood, and the preparation method of the manganese complex has the advantages of mild condition, short period, simple operation condition and the like. The catalyst is used for reducing the chiral alcohol for ketone hydrogen transfer, has higher catalytic activity, and a method for preparing the chiral alcohol is simple, less in environment pollution, and high in yield.
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Paragraph 0063-0066; 0069-0079

(2020/01/03)

Compartmentalized Nanoreactors for One-Pot Redox-Driven Transformations
This contribution introduces poly(2-oxazoline)-based shell cross-linked micelles (SCMs) as nanoreactors to realize one-pot redox-driven deracemizations of secondary alcohols in aqueous media. TEMPO and Rh-TsDPEN moieties are spatially positioned into the hydrophilic corona and the hydrophobic micelle core, respectively. TEMPO catalyzes the oxidation of racemic secondary alcohols into ketones, while Rh-TsDPEN catalyzes the asymmetric transfer hydrogenation (ATH) of these ketones to afford enantioenriched secondary alcohols. Both catalysts, the Rh-TsDPEN complex and TEMPO, are incompatible with each other and the SCMs are designed to provide indispensable catalyst site isolation. Kinetic studies show that the SCMs enhance the reactivity of the immobilized catalysts, in comparison to those for the unsupported analogues under the same reaction conditions. Our nanoreactors can perform deracemizations on a broad range of secondary alcohol substrates and are reusable in a continuous manner while maintaining high activity.
Qu, Peiyuan,Kuepfert, Michael,Jockusch, Steffen,Weck, Marcus
p. 2701 - 2706
(2019/03/08)

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.
Wang, Yanzhao,Yang, Guoqiang,Xie, Fang,Zhang, Wanbin
supporting information
p. 6135 - 6139
(2018/09/27)

Synthesis of Enantiomerically Pure and Racemic Benzyl-Tethered Ru(II)/TsDPEN Complexes by Direct Arene Substitution: Further Complexes and Applications
The use of a direct arene-exchange method for the synthesis of benzyl-tethered arene/Ru/TsDPEN complexes for use in asymmetric transfer hydrogenation is reported. A series of complexes tethered through a three-carbon linear chain was also prepared. The arene-exchange approach significantly simplifies the synthetic approach to this class of catalyst and permits the ready formation of modified analogues. The approach also provides a route to racemic catalysts for use in general reductions with either hydrogen or transfer hydrogenation.
Soni, Rina,Jolley, Katherine E.,Gosiewska, Silvia,Clarkson, Guy J.,Fang, Zhijia,Hall, Thomas H.,Treloar, Ben N.,Knighton, Richard C.,Wills, Martin
p. 48 - 64
(2018/01/17)

Enantioconvergent Biocatalytic Redox Isomerization
Alcohol dehydrogenases can act as powerful catalysts in the preparation of optically pure γ-hydroxy-δ-lactones by means of an enantioconvergent dynamic redox isomerization of readily available Achmatowicz-type pyranones. Imitating the traditionally metal-
Liu, Yu-Chang,Merten, Christian,Deska, Jan
supporting information
p. 12151 - 12156
(2018/09/11)

Total Synthesis and Biological Evaluation of the Glycosylated Macrocyclic Antibiotic Mangrolide A
The macrocyclic antibiotic mangrolide A has been described to exhibit potent activity against a number of clinically important Gram-negative pathogens. Reported is the first enantioselective total synthesis of mangrolide A and derivatives. Salient features of this synthesis include a highly convergent macrocycle preparation, stereoselective synthesis of the disaccharide moiety, and two β-selective glycosylations. The synthesis of mangrolide A and its analogues enabled the re-examination of its activity against bacterial pathogens, and only minimal activity was observed.
Hattori, Hiromu,Roesslein, Joel,Caspers, Patrick,Zerbe, Katja,Miyatake-Ondozabal, Hideki,Ritz, Daniel,Rueedi, Georg,Gademann, Karl
supporting information
p. 11020 - 11024
(2018/07/31)

Asymmetric transfer hydrogenation of acetophenone derivatives using 2-benzyl-tethered ruthenium (II)/TsDPEN complexes bearing η6-(p-OR) (R = H, iPr, Bn, Ph) ligands
A series of 4′-OR (R = H, iPr, Bn, Ph) substituted ruthenium (II) biphenyl TsDPEN complexes are described; the complexes are accessed via an operationally simple and reliable two-step ligand synthesis followed by ligation to the ruthenium (II) centre. We report the preliminary asymmetric transfer hydrogenation (ATH) results on a range of primarily acetophenone derivatives with these new complexes using FA/TEA (5:2) as a reducing agent; the results confirm that these catalysts are capable of reducing the substrates within 48 h with excellent enantioselectivities.
Knighton, Richard C.,Vyas, Vijyesh K.,Mailey, Luke H.,Bhanage, Bhalchandra M.,Wills, Martin
p. 72 - 79
(2018/09/22)

Iridium and Rhodium Complexes Containing Enantiopure Primary Amine-Tethered N-Heterocyclic Carbenes: Synthesis, Characterization, Reactivity, and Catalytic Asymmetric Hydrogenation of Ketones
The imidazolium salt [(S,S)-tBuNC3H3NCHPhCHPhNH2]PF6, (S,S)-11·HPF6 is a precursor to the enantiopure "Kaibene" ligand, tBu-Kaibene, (S,S)-11 featuring a tert-butyl group on the N-heterocyclic carbene (NHC) ring-nitrogen atoms. It has been prepared in high yield and purity by refluxing a chiral cyclic sulfamidate with 1-tert-butylimidazole. Similarly (S,S)-12·HPF6 with a mesityl group at the imidazolium ring-nitrogen atom has been prepared in the same fashion and serves as a source of Mes-Kaibene, (S,S)-12. These bidentate Kaibene ligands feature an NHC and a primary amine separated by a chiral linker. Salts (S,S)-11·HPF6 or (S,S)-12·HPF6 react with base and AgI or CuI to give a total of four M(Kaibene)2I compounds (M = Ag or Cu). At 22 °C, the amine-functionalized imidazolium cations undergo oxidative addition to iridium(I) in [IrCl(cod)]2 (cod = 1,5-cyclooctadiene) to generate iridium(III) hydride R-Kaibene compounds [IrHCl(cod)((S,S)-11)](PF6) (17) and [IrHCl(cod)((S,S)-12)](PF6) (18), respectively, each as a mixture of six configurational isomers. In contrast, the salt (S,S)-11·HPF6 reacts with [Ir(OtBu)(cod)]2 to produce a bimetallic iridium compound with (S,S)-11 as the bridging ligand. This compound contains interesting NH···Cl and NH···Ir noncovalent intramolecular interactions. Salt (S,S)-12·HPF6 reacts with silver oxide to yield [Ag2((S,S)-12)2](PF6)2 (20). Reagent 20 serves as an efficient transmetalation reagent to deliver to each rhodium in [RhCl(cod)]2 1 equiv of (S,S)-12 as a bidentate ligand to give [Rh(cod)((S,S)-12)](PF6). In the reaction between [IrCl(cod)]2 and 20, (S,S)-12 ends up coordinated in an iridium(III) hydride complex (22) as a tridentate ligand via the NHC, NH2, and a cyclometalated phenyl group. The two iridium hydride compounds, 18 and 22, are catalysts for the hydrogenation of a range of ketones (turnover number up to 499, turnover frequency up to 249 h-1, with er (enantiomeric ratio) up to 35:65 R:S).
Wan, Kai Y.,Roelfes, Florian,Lough, Alan J.,Hahn, F. Ekkehardt,Morris, Robert H.
supporting information
p. 491 - 504
(2018/02/17)

CHIRAL METAL COMPLEX COMPOUNDS
The invention comprises novel chiral metal complex compounds of the formula (I) wherein M, PR2, R3 and R4 are outlined in the description, its stereoisomers, in the form as a neutral complex or a complex cation with a suitable counter ion. The chiral metal complex compounds can be used in asymmetric reactions, particularly in asymmetric reductions of ketones, imines or oximes.
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Page/Page column 18; 19; 20

(2018/11/10)

Piano-stool Ru(II)-benzene complexes bearing D/L-alanine derived chiral aroylthiourea ligands for asymmetric transfer hydrogenation of ketones in water
Abstract: The new water soluble chiral Ru(II)-benzene complexes of the type [RuCl 2(η6-C 6H 6) L] were obtained from the reactions between [RuCl2(η6-C6H6)]2 and the chiral aroylthiourea ligands (L) derived from unprotected D/L-alanine and characterized. The solid-state structure of representative complexes was confirmed by single crystal X-ray diffraction technique. The Ru(II)-benzene complexes catalyzed the asymmetric transfer hydrogenation (ATH) of aromatic ketones to their enantiopure secondary alcohols. The reactions were carried out in the presence of formic acid–triethylamine mixture in water, and the product alcohols were obtained with excellent conversions (up to 99%) and enantiomeric excesses (up to 99%). The scope of the catalytic system was extended to various aromatic ketones. The catalytic activity of the present water-soluble Ru-benzene complexes toward enantioselective reduction of ketones was considerably higher than that of p-cymene analogues in water. Graphical Abstract: The water-soluble chiral Ru(II)-benzene complexes were produced from the reactions between [RuCl2(η6-C6H6)]2 and the chiral aroylthiourea ligands derived from unprotected D/L-alanine. The catalytic activity of the Ru(II)-benzene complexes toward enantioselective reduction of ketones was found to be good in water medium.[Figure not available: see fulltext.].
Sheeba, Mani Mary,Bhuvanesh, Nattamai S P,Karvembu, Ramasamy
(2018/12/04)

Lipase-Induced Oxidative Furan Rearrangements
Lipase B from Candida antarctica catalyzes the oxidative ring expansion of furfuryl alcohols using aqueous hydrogen peroxide to yield functionalized pyranones under mild conditions. The method further allows for the preparation of corresponding piperidinone derivatives by enzymatic rearrangement of N-protected furfurylamines.
Blume, Fabian,Sprengart, Petra,Deska, Jan
p. 1293 - 1296
(2018/01/27)

Development of Ferrocene-Based Diamine-Phosphine-Sulfonamide Ligands for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones
A series of air-stable, easily accessible tridentate ferrocene-based diamine-phosphine sulfonamide (f-diaphos) ligands were successfully developed for iridium-catalyzed asymmetric hydrogenation of ketones. The f-diaphos ligands exhibited excellent enantioselectivity and superb reactivity in Ir-catalyzed asymmetric hydrogenation of ketones (for arylalkyl ketones, (S)-selectivity, up to 99.4% ee, and 100 000 TON; for diaryl ketones, (R)-selectivity, up to 98.2% ee, and 10 000 TON). This protocol could be easily conducted on gram scale, thereby providing a chance to various drugs.
Ling, Fei,Nian, Sanfei,Chen, Jiachen,Luo, Wenjun,Wang, Ze,Lv, Yaping,Zhong, Weihui
p. 10749 - 10761
(2018/09/06)

The open d-shell enforces the active space in 3d metal catalysis: Highly enantioselective chromium(ii) pincer catalysed hydrosilylation of ketones
Bis(oxazolinyldimethylmethyl)pyrrol (PdmBox) stereodirecting ligands provided the key to the chromium(ii)-catalysed highly enantioselective hydrosilylation of ketones. A rare square planar, chiral chromium(ii) alkyl complex was found to serve as a potent precatalyst for the reduction of a broad range of aryl alkyl and dialkyl ketone derivatives. The stereoelectronic preference of the open d4 shell of chromium(ii) firmly locks the molecular catalyst in a square planar geometry giving rise to two blocked quadrants of the coordination sphere. This earth-abundant base metal catalytic platform produces the corresponding chiral alcohols in excellent isolated yields with up to 98 %ee under mild reaction conditions (-40 °C to rt) and at low catalyst loadings (as low as 0.5 mol%).
Schiwek, Christian H.,Vasilenko, Vladislav,Wadepohl, Hubert,Gade, Lutz H.
supporting information
p. 9139 - 9142
(2018/08/24)

Tridentate nitrogen phosphine ligand and complex and application thereof in asymmetric catalytic hydrogenation of ketone
The invention belongs to the field of organic and medicine synthetic chemistry, and discloses a tridentate nitrogen phosphine ligand. The tridentate nitrogen phosphine ligand has a structure shown ina formula I which is shown in the attached figure, wherein R1 is toluene sulfonyl or 2,4,6-triisopropylbenzenesulfonyl, and R2 is aryl or substituted aryl. The invention also discloses a complex of the tridentate nitrogen phosphine ligand; the complex is prepared by mixing the tridentate nitrogen phosphine ligand and a transition metal complex; the complex is used for asymmetric catalytic hydrogenation of ketone. The tridentate nitrogen phosphine ligand has the advantages that 1, the synthesizing is easy, and the chiral ligand can be prepared by only two to three reaction steps; 2, the ligandis stable, the series of ligand is not sensitive to water and oxygen, and the convenience in storage and use is realized; 3, the catalyzing effect is good, and the catalyst can be used for realizing 100% of conversion and 99% of stereo selectivity on most of suitable primers; 4, the atom economy is high, and the activity of the catalysis system is higher; for most of suitable primers, the conversion number reaches more than 10000, and the maximum conversion number reaches 200000.
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Paragraph 0119; 0120; 0121; 0122

(2018/04/03)

Scope and Mechanism on Iridium-f-Amphamide Catalyzed Asymmetric Hydrogenation of Ketones
A series of novel and easily accessed ferrocene-based amino-phosphine-sulfonamide (f-Amphamide) ligands have been developed and applied in Ir-catalyzed asymmetric hydrogenation of aryl ketones, affording the corresponding chiral secondary alcohols with excellent results (up to >99% conversion, >99% ee and TON up to 200 000). DFT calculations suggest an activating model involving an alkali cation Li+.
Liang, Zhiqin,Yang, Tilong,Gu, Guoxian,Dang, Li,Zhang, Xumu
p. 851 - 856
(2018/07/31)

Chloroperoxidase-Catalyzed Achmatowicz Rearrangements
Chloroperoxidase from Caldariomyces fumago catalyzes the selective oxidation of furfuryl alcohols in an Achmatowicz-type ring expansion. In combination with glucose oxidase as oxygen-activating biocatalyst, a purely enzymatic, aerobic protocol for the synthesis of 6-hydroxypyranone building blocks is obtained. Thanks to an only modest stereochemical bias of the oxygenating heme protein, optically active alcohols of either configuration are converted without a significant mismatch opening up opportunities for enantioselective multienzymatic cascades. Balancing the oxidase-driven aerobic activation, extended enzyme half-lives and productive conversion of poorly soluble and slowly reacting substrates can be achieved with high yields of the six-membered O-heterocycles.
Thiel, Daniel,Blume, Fabian,J?ger, Christina,Deska, Jan
p. 2717 - 2725
(2018/05/14)

Asymmetric Transfer Hydrogenation of (Hetero)arylketones with Tethered Rh(III)-N-(p-Tolylsulfonyl)-1,2-diphenylethylene-1,2-diamine Complexes: Scope and Limitations
A series of new tethered Rh(III)/Cp? complexes containing the N-(p-tolylsulfonyl)-1,2-diphenylethylene-1,2-diamine ligand have been prepared, characterized, and evaluated in the asymmetric transfer hydrogenation (ATH) of a wide range of (hetero)aryl ketones. The reaction was performed under mild conditions with the formic acid/triethylamine (5:2) system as the hydrogen source and provided enantiomerically enriched alcohols with good yields and high to excellent enantioselectivities. Although the nature of the substituents on the phenyl tethering ring did not alter the stereochemical outcome of the reaction, complexes bearing electron-donating groups exhibited a higher catalytic activity than those having electron-withdrawing groups. A scale-up of the ATH of 4-chromanone to the gram scale quantitatively delivered the reduced product with excellent enantioselectivity, demonstrating the potential usefulness of these new complexes.
Zheng, Long-Sheng,Llopis, Quentin,Echeverria, Pierre-Georges,Férard, Charlène,Guillamot, Gérard,Phansavath, Phannarath,Ratovelomanana-Vidal, Virginie
p. 5607 - 5615
(2017/06/07)

Iridium-Catalyzed Asymmetric Hydrogenation of Ketones with Accessible and Modular Ferrocene-Based Amino-phosphine Acid (f-Ampha) Ligands
A series of tridentate ferrocene-based amino-phosphine acid (f-Ampha) ligands have been successfully developed. The f-Ampha ligands are extremely air stable and exhibited excellent performance in the Ir-catalyzed asymmetric hydrogenation of ketones (full conversions, up to >99% ee, and 500?000 TON). DFT calculations were performed to elucidate the reaction mechanism and the importance of the COOH group. Control experiments also revealed that the COOH group played a key role in this reaction.
Yu, Jianfei,Long, Jiao,Yang, Yuhong,Wu, Weilong,Xue, Peng,Chung, Lung Wa,Dong, Xiu-Qin,Zhang, Xumu
supporting information
p. 690 - 693
(2017/02/10)

Highly Enantioselective Hydrosilylation of Ketones Catalyzed by a Chiral Oxazaborolidinium Ion
A highly enantioselective hydrosilylation of ketones was developed for the synthesis of a variety of chiral secondary alcohols. In the presence of a chiral oxazaborolidinium ion (COBI) catalyst, the reaction proceeded with good yields (up to 99%) with excellent enantioselectivities (up to 99% ee).
Kang, Byung Chul,Shin, Sung Ho,Yun, Jaesook,Ryu, Do Hyun
supporting information
p. 6316 - 6319
(2017/12/08)

Asymmetric hydrogenation of pro-chiral ketones catalyzed by chiral Ru(II)-benzene organometallic compounds containing amino acid based aroylthiourea ligands
A series of Ru(II)-benzene organometallic compounds (1–6) constructed from [RuCl2(η6-benzene)]2and chiral aroylthiourea ligands (L1-L6) obtained from D/L-phenylalanine, was fully characterized. The chiral complexes along with 2-propanol and NaOH effected the asymmetric hydrogenation of aromatic ketones at 82?°C within 8–10?h. The reduction reactions proceeded with excellent conversions and enantiomeric excesses (up to 99%).
Sheeba, M. Mary,Tamizh, M. Muthu,Farrugia,Karvembu
p. 45 - 49
(2017/01/16)

Manganese(I)-Catalyzed Enantioselective Hydrogenation of Ketones Using a Defined Chiral PNP Pincer Ligand
A new chiral manganese PNP pincer complex is described. The asymmetric hydrogenation of several prochiral ketones with molecular hydrogen in the presence of this complex proceeds under mild conditions (30–40 °C, 4 h, 30 bar H2). Besides high catalytic activity for aromatic substrates, aliphatic ketones are hydrogenated with remarkable selectivity (e.r. up to 92:8). DFT calculations support an outer sphere hydrogenation mechanism as well as the experimentally determined stereochemistry.
Garbe, Marcel,Junge, Kathrin,Walker, Svenja,Wei, Zhihong,Jiao, Haijun,Spannenberg, Anke,Bachmann, Stephan,Scalone, Michelangelo,Beller, Matthias
supporting information
p. 11237 - 11241
(2017/09/02)

NHTs Effect on the Enantioselectivity of Ru(II) Complex Catalysts Bearing a Chiral Bis(NHTs)-Substituted Imidazolyl-Oxazolinyl-Pyridine Ligand for Asymmetric Transfer Hydrogenation of Ketones
Pincer-type ruthenium(II)-NNN complex catalysts bearing a chiral bis(NHTs)-substituted imidazolyl-oxazolinyl-pyridine ligand were synthesized and structurally characterized by NMR, IR, elemental analysis, and X-ray single-crystal crystallographic determinations. The two NHTs groups substituted on the imidazolyl moiety of the chiral NNN ligand exhibited a remarkable effect on the enantioselectivity of the Ru(II)-NNN complexes for the asymmetric transfer hydrogenation (ATH) of ketones. The Ru(II)-NNN complex bearing a chiral (NHTs)2-substituted imidazolyl-(isopropyl)oxazolinyl-pyridine ligand exhibited excellent catalytic activity, reaching an enantioselectivity up to 99.9% ee for the target alcohol products.
Chai, Huining,Liu, Tingting,Yu, Zhengkun
p. 4136 - 4144
(2017/11/21)

Enantioselective reduction of aryl and hetero aryl methyl ketones using plant cell suspension cultures of Vigna radiata
Vigna radiata was investigated as whole cell catalyst for the bioreduction of aryl and heteroaryl prochiral ketones into optically active alcohols. The study indicates selective bioreduction of different substituted aryl and heteroaryl ketones (1a–12a) to their respective (S)–chiral alcohols (1b–12b) in good to high enantioselectivity (77.7–97.5%) with very good yields (73–82%). The results obtained confirm that the keto reductase has broad substrate specificity and selectivity in catalyzing both six and five-membered heteroaryl methyl ketones. The current methodology substantiates a promising and alternative green approach for the synthesis of secondary chiral alcohols of biological importance in a mild, cheap and environmentally benign process.
Santhanam, Srinath,Patil, Swati,Shanmugam, Ramu,Dronamraju V.L, Sarada,Balasundaram, Usha,Baburaj, Baskar
p. 223 - 229
(2017/06/09)

Total Synthesis of (?)-Angiopterlactone B
An enantioselective total synthesis of (?)-angiopterlactone B has been accomplished in four steps. The synthesis features a proposed biomimetic domino ring-contraction/oxa-Michael/Michael dimerization sequence, forming three new bonds, two new rings, and
Thomson, Marie I.,Nichol, Gary S.,Lawrence, Andrew L.
supporting information
p. 2199 - 2201
(2017/05/12)

Unsymmetrical Iron P-NH-P′ Catalysts for the Asymmetric Pressure Hydrogenation of Aryl Ketones
The reductive amination of α-dialkylphosphine acetaldehydes with enantiopure β-aminophosphines is a new, versatile route to unsymmetrical tridentate (pincer) ligands P-NH-P′. Four new ligands PR2CH2CH2NHCHR′CHR′′PPh2 (R=iPr, Cy, R′=Ph, CH(CH3)2, R′′=Ph, H) prepared in this way are used to make the iron(II) complexes mer-FeCl2(CO)(P-NH-P′) and mer-FeCl(H)(CO)(P-NH-P′). The hydride complex with the rigid ligand with R′=R′′=Ph is an efficient and highly enantioselective homogeneous asymmetric pressure hydrogenation (APH) catalyst. Prochiral aryl ketones are reduced under mild conditions (THF, 0.1 mol % catalyst, 1 mol % KOtBu, 5–10 bar, 50 °C) to the (S)-alcohols, usually in enantiomeric excess (ee) greater than 90 %. DFT calculations provided transition-state structures for the enantiodetermining hydride-transfer step.
Smith, Samantha A. M.,Lagaditis, Paraskevi O.,Lüpke, Anne,Lough, Alan J.,Morris, Robert H.
p. 7212 - 7216
(2017/05/31)

Use of the Trost Ligand in the Ruthenium-Catalyzed Asymmetric Hydrogenation of Ketones
The Trost ligand, (1S,2S)-1,2-diaminocyclohexane-N,N′-bis(2′-diphenylphosphinobenzoyl) (L), is reported for the first time as a ligand for the asymmetric hydrogenation (AH) of ketones. Ligand (S,S)-L was screened in the presence of several metal salts and was found to form active catalysts if combined with ruthenium sources in the presence of hydrogen and a base. Reaction optimization was performed by screening different Ru sources, solvents, and bases. Under the optimized conditions, the complex formed by the combination of (S,S)-L with RuCl3(H2O)x in the presence of Na2CO3 was able to promote the AH of several ketones at room temperature in good yields with up to 96 % ee. The reaction kinetics measured under the optimized conditions revealed the presence of a long induction period, during which the initially formed Ru species was transformed into the catalytically active complex by reaction with hydrogen. Remarkably, a ketone that is a precursor of the antiemetic drug aprepitant was hydrogenated in excellent yield with a good ee value.
Cettolin, Mattia,Puylaert, Pim,Pignataro, Luca,Hinze, Sandra,Gennari, Cesare,de Vries, Johannes G.
p. 3125 - 3130
(2017/08/29)

Mechanism-Based Enantiodivergence in Manganese Reduction Catalysis: A Chiral Pincer Complex for the Highly Enantioselective Hydroboration of Ketones
A manganese alkyl complex containing a chiral bis(oxazolinyl-methylidene)isoindoline pincer ligand is a precatalyst for a catalytic system of unprecedented activity and selectivity in the enantioselective hydroboration of ketones, thus producing preparatively useful chiral alcohols in excellent yields with up to greater than 99 % ee. It is applicable for both aryl alkyl and dialkyl ketone reduction under mild reaction conditions (TOF >450 h?1 at ?40 °C). The earth-abundant base-metal catalyst operates at very low catalyst loadings (as low as 0.1 mol %) and with a high level of functional-group tolerance. There is evidence for the existence of two distinct mechanistic pathways for manganese-catalyzed hydride transfer and their role for enantiocontrol in the selectivity-determining step is presented.
Vasilenko, Vladislav,Blasius, Clemens K.,Wadepohl, Hubert,Gade, Lutz H.
supporting information
p. 8393 - 8397
(2017/07/11)