- Chiral (η6-p-cymene)ruthenium(II) complexes containing monodentate acylthiourea ligands for efficient asymmetric transfer hydrogenation of ketones
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The new chiral ligands (R)-/(S)-N-((1-phenylethyl)carbamothioyl)benzamide (L1/L2), (R)-/(S)-N-((1-phenylethyl)carbamothioyl)thiophene-2-carboxamide (L3/L4), and (R)-/(S)-N-((1-phenylethyl)carbamothioyl)furan-2-carboxamide (L5/L6) were synthesized, characterized, and used to prepare novel chiral Ru(II) complexes. The chiral Ru(II) complexes 1-6 were obtained from reactions between the chiral ligands L1-L6 and [RuCl2(p-cymene)2] 2. The complexes were characterized by analytical and spectroscopic (NMR, FT-IR, electronic) techniques. The solid-state structures of the ligands L1 and L3 and complexes 1, 4, and 6 were determined by single-crystal X-ray diffraction methods. In all of the complexes, the ligand is bound to the Ru(II) center only via the sulfur donor atom. This monodentate coordination of the acylthiourea ligands was observed for the first time with ruthenium. The Ru(II) complexes 1-6 all act as efficient catalysts for the asymmetric transfer hydrogenation of aromatic ketones in the presence of 2-propanol and KOH to produce chiral alcohols. All of the catalysts showed excellent conversions of up to 99% and enantiomeric excesses of up to 99%.
- Sheeba, Mani Mary,Muthu Tamizh, Manoharan,Farrugia, Louis J.,Endo, Akira,Karvembu, Ramasamy
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- Boron containing chiral Schiff bases: Synthesis and catalytic activity in asymmetric transfer hydrogenation (ATH) of ketones
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Asymmetric Transfer Hydrogenation (ATH) has been an attractive way for the reduction of ketones to chiral alcohols. A great number of novel and valuable synthetic pathways have been achived by the combination usage of organometallic and coordination chemistry for the production of important class of compounds and particularly optically active molecules. For this aim, four boron containing Schiff bases were synthesized by the reaction of 4-formylphenylboronic acid with chiral amines. The boron containing structures have been found as stable compounds due to the presence of covalent B–O bonds and thus could be handled in laboratory environment. They were characterized by 1H NMR and FT-IR spectroscopy and elemental analysis and they were used as catalyst in the transfer hydrogenation of ketones to the related alcohol derivatives with high conversions (up to 99%) and low enantioselectivities (up to 22% ee).
- Pa?a, Salih,Arslan, Nevin,Meri??, Nermin,Kayan, Cezmi,Bingül, Murat,Durap, Feyyaz,Aydemir, Murat
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- Production of enantiomerically enriched chiral carbinols using Weissella paramesenteroides as a novel whole cell biocatalyst
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In this study, four bacterial strains were tested for their ability to reduce acetophenones to its corresponding alcohol. Among these strains Weissella paramesenteroides N7 was found to be the most successful biocatalyst to reduce the ketones to the corresponding alcohols. The reaction conditions were systematically optimized for W. paramesenteroides N7 that resulted in high enantioselectivity and conversion rates for the bioreduction. The scale-up asymmetric reduction of 1-(4-methoxyphenyl) propan-1-one (1r) by W. paramesenteroides N7 gave (R)-1-(4-methoxyphenyl) propan-1-ol (2r) with 94% yield and >99% enantiomeric excess. This is the first report showing the synthesis of (R)-1-(4-methoxyphenyl) propan-1-ol (2r) in enantiopure form using a biocatalyst on a gram scale. The whole cell catalyzed the reductions of ketone substrates on the preparative scale, demonstrating that W. paramesenteroides N7 would be a valuable biocatalyst for the preparation of chiral aromatic alcohols of pharmaceutical interest as a promising and alternative green approach.
- Tozlu, Caner,?ahin, Engin,Serencam, Hüseyin,Dertli, Enes
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- Highly Enantioselective Transfer Hydrogenation of Prochiral Ketones Using Ru(II)-Chitosan Catalyst in Aqueous Media
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Unprecedentedly high enantioselectivities are obtained in the transfer hydrogenation of prochiral ketones catalyzed by a Ru complex formed in situ with chitosan chiral ligand. This biocompatible, biodegradable chiral polymer obtained from the natural chitin afforded good, up to 86 % enantioselectivities, in the aqueous-phase transfer hydrogenation of acetophenone derivatives using HCOONa as hydrogen donor. Cyclic ketones were transformed in even higher, over 90 %, enantioselectivities, whereas further increase, up to 97 %, was obtained in the transfer hydrogenations of heterocyclic ketones. The chiral catalyst precursor prepared ex situ was examined by scanning electron microscopy, FT-mid- and -far-IR spectroscopy. The structure of the in situ formed catalyst was investigated by 1H NMR spectroscopy and using various chitosan derivatives. It was shown that a Ru pre-catalyst is formed by coordination of the biopolymer to the metal by amino groups. This precursor is transformed in water insoluble Ru-hydride complex following hydrogen donor addition. The practical value of the developed method was verified by preparing over twenty chiral alcohols in good yields and optical purities. The catalyst was applied for obtaining optically pure chiral alcohols at gram scale following a single crystallization.
- Sz?ll?si, Gy?rgy,Kolcsár, Vanessza Judit
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- A new class of well-defined ruthenium catalysts for enantioselective transfer hydrogenation of various ketones
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A pair of novel optically pure phosphinite ligands were synthesized by ring opening reaction of chiral amines with (R)-styrene oxide or (S)-glycidyl phenyl ether oxide using a straightforward method in high yields and their ruthenium complexes were described in detail. The ruthenium complexes proved to be highly efficient catalysts for the enantioselective hydrogenation of ketones, affording products up to 99% ee. The results showed that the corresponding chiral alcohols could be obtained with high activity and excellent enantioselectivities at the desired temperature. (2S)-1-{benzyl[(1S)-1-(naphthalen-1-yl)ethyl]amino}-3-phenoxypropan-2-yl diphenylphosphinito[dichloro(η6-benzene)ruthenium (II)] acts an excellent catalyst in the reduction of ketones, giving the corresponding alcohol up to 99% ee.
- Kayan, Cezmi,Meri?, Nermin,Rafikova, Khadichakhan,Zazybin, Alexey,Gürbüz, Nevin,Karakaplan, Mehmet,Aydemir, Murat
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- Asymmetric reduction of prochiral aromatic and hetero aromatic ketones using whole-cell of Lactobacillus senmaizukei biocatalyst
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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
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- Catalysts for the asymmetric transfer hydrogenation of various ketones from [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] and [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2
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The combination of [3-[(2S)-2-[(diphenylphosphanyl)oxy]-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride] with [Ru(η6-arene)(μ-Cl)Cl]2, Ir(η5-C5Me5)(μ-Cl)Cl]2 or [Rh(μ-Cl)(cod)]2, in the presence of KOH/isoPrOH, has been found to generate catalysts that are capable of enantioselectively reducing alkyl, aryl ketones to the corresponding (R)-alcohols. Under optimized conditions, when the catalysts were applied to the asymmetric transfer hydrogenation, we obtained the secondary alcohol products in high conversions and enantioselectivities using only 0.5 mol% catalyst loading. In addition, [3-[(2S)-2-{[(chloro(?4-1,5-cyclooctadiene)rhodium)diphenyl phosphanyl] oxy}-3-phenoxypropyl]-1-methyl-1H-imidazol-3-ium chloride], (6) complex is much more active than the other analogous complexes in the transfer hydrogenation. Catalyst 6 acts as excellent catalysts, giving the corresponding (R)-1-phenyl ethanol in 99% conversion in 30 min (TOF ≤ 396 h?1) and in high enantioselectivity (92% ee).
- Meri?, Nermin,Arslan, Nevin,Kayan, Cezmi,Rafikova, Khadichakhan,Zazybin, Alexey,Kerimkulova, Aygul,Aydemir, Murat
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- Application of copper(II)-dipyridylphosphine catalyst in the asymmetric hydrosilylation of simple ketones in air
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Copper (II)-dipyridylphosphine catalyst was used in the asymmetric hydrosilylation of simple ketones under ambient conditions in competitive levels of enantioinduction and activity. The experiment also described the utility of the combination of copper(II) salt/(S)-1/PhSiH3 in the enantioselective hydrosilylation of heteroaromatic ketones and several other ketonic substrates leading to some valuable pharmaceutical and agricultural chemical intermediates. A number of the resulting chiral alcohols represented valuable intermediates for some physiologically active compounds, with remarkable temperature effects on the asymmetric induction were observed in some cases of heteroaromatic ketones. The results show that the present catalyst system features widespread substrate scope, high air stability, fast rate of reaction, good-to-excellent enantioselectivity, and mild conditions thereby affording a practical protocol to a vast selection of optically enriched alcohols.
- Zhang, Xi-Chang,Wu, Yan,Yu, Feng,Wu, Fei-Fei,Wu, Jing,Chan, Albert S. C.
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- New functional chiral P-based ligands and application in ruthenium-catalyzed enantioselective transfer hydrogenation of ketones
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Metal-catalyzed asymmetric transfer hydrogenation is a powerful and practical method for the reduction of ketones to produce the corresponding secondary alcohols, which are valuable building blocks in the pharmaceutical, perfume, and agrochemical industries. Hence, a series of novel chiral β-amino alcohols were synthesized by chiral amines with regioselective ring opening of (S)-propylene oxide or reaction with (S)-(+)-2-hydroxypropyl p-toluenesulfonate by a straightforward method. The chiral ruthenium catalytic systems generated from [Ru(arene)(μ-Cl)Cl]2 complexes and chiral phosphinite ligands based on amino alcohol derivatives were employed in asymmetric transfer hydrogenation of ketones to give the corresponding optically active alcohols; (2S)-1-{[(2S)-2-[(diphenylphosphanyl)oxy]propyl][(1R)-1-phenylethyl]amino}propan-2-yldiphenylphosphinitobis[dichol-oro(η6-benzene)ruthenium(II)] acts an excellent catalyst in the reduction of α-naphthyl methyl ketone, giving the corresponding alcohol with up to 99% ee. The substituents on the backbone of the ligands were found to have a remarkable effect on both the conversion and enantioselectivity of the catalysts. Furthermore, this transfer hydrogenation is characterized by low reversibility under these conditions.
- Meri?, Nermin,Kayan, Cezmi,Gürbüz, Nevin,Karakaplan, Mehmet,Binbay, Nil Ertekin,Aydemir, Murat
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- Bioreduction of prochiral ketones by growing cells of Lasiodiplodia theobromae: Discovery of a versatile biocatalyst for asymmetric synthesis
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Growing cells of the phytopathogen fungus Lasiodiplodia theobromae in potato dextrose broth have shown their potential for the stereoselective bioreduction of different prochiral aromatic and aliphatic ketones. Optically active alcohols were obtained under mild reaction conditions in high conversions (up to 90%) and moderate to excellent enantioselectivity (35-≥99% ee) depending on the ketone structure. Prelog alcohols were isolated, except in the bioreduction of cyclohexylmethylketone and octan-2-one where anti-Prelog alcohols were obtained.
- Barros-Filho, Bartholomeu A.,Nunes, Fatima M.,de Oliveira, Maria da Conceicao F.,Lemos, Telma L.G.,de Mattos, Marcos C.,de Gonzalo, Gonzalo,Gotor-Fernandez, Vicente,Gotor, Vicente
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- Enantioselective reduction of aryl and hetero aryl methyl ketones using plant cell suspension cultures of Vigna radiata
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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
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- When does an intermediate become a transition state? Degenerate isomerization without competing racemization during solvolysis of (S)-1-(3-nitrophenyl)ethyl tosylate
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(S)-1-(3-Nitrophenyl)ethyl tosylate [(S)-2-OTs] was prepared in >99% enantiomeric excess and the change in the chiral purity of this compound was monitored during solvolysis in 50:50 trifluoroethanol/water. The barely detectable formation of 0.5% (R)-2-OT
- Tsuji, Yutaka,Richard, John P.
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- Candida tropicalis CE017: A new Brazilian enzymatic source for the bioreduction of aromatic prochiral ketones
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The reactivity and stereoselectivity showed by a new strain of Candida tropicalis in the reduction of prochiral ketones have been compared with the ones previously attained in our laboratory using microorganisms from the Brazilian biodiversity. In this manner, Candida tropicalis has demonstrated its versatility as stereoselective agent in the bioreduction of a series of aromatic ketones. These prochiral compounds were converted into their corresponding optically alcohols with moderate to excellent stereopreference depending on the substrate structure. Among ketones tested, nitroacetophenones were enzymatically reduced to enantiopure (S)-alcohol with complete conversion.
- Vieira, Gizelle A. B.,De Freitas Araujo, Daniel M.,Lemos, Telma L. G.,De Mattos, Marcos Carlos,Da Conceic?a?o F. De Oliveira, Maria,Melo, Va?nia M. M.,De Gonzalo, Gonzalo,Gotor-Ferna?ndez, Vicente,Gotor, Vicente
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- Mechanochemical, Water-Assisted Asymmetric Transfer Hydrogenation of Ketones Using Ruthenium Catalyst
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Asymmetric catalytic reactions are among the most convenient and environmentally benign methods to obtain optically pure compounds. The aim of this study was to develop a green system for the asymmetric transfer hydrogenation of ketones, applying chiral Ru catalyst in aqueous media and mechanochemical energy transmission. Using a ball mill we have optimized the milling parameters in the transfer hydrogenation of acetophenone followed by reduction of various substituted derivatives. The scope of the method was extended to carbo- and heterocyclic ketones. The scale-up of the developed system was successful, the optically enriched alcohols could be obtained in high yields. The developed mechanochemical system provides TOFs up to 168 h?1. Our present study is the first in which mechanochemically activated enantioselective transfer hydrogenations were carried out, thus, may be a useful guide for the practical synthesis of optically pure chiral secondary alcohols.
- Kolcsár, Vanessza Judit,Sz?ll?si, Gy?rgy
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- Arene-Immobilized Ru(II)/TsDPEN Complexes: Synthesis and Applications to the Asymmetric Transfer Hydrogenation of Ketones
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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.
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supporting information
p. 226 - 235
(2020/12/31)
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- One-pot kinetic resolution-Mitsunobu reaction to access optically pure compounds, using silver salts in the substitution protocol
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A practical method is developed to access chiral arylalkyl carbinols with a high yield from racemic alcohols. A one-pot enzyme mediated Kinetic Resolution followed by Mitsunobu esterification of the unreacted enantiomer of alcohol with metal acetate results in a nearly complete formation of chiral acetate. Substitution with AgOAc was found to be the most efficient, and the use of sub stoichiometric amounts of AgNO3 and excess of NaOAc affords comparable results; the protocol was further extended to introduce azide as a nucleophile.
- Raval, Hiten B.,Bedekar, Ashutosh V.
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p. 21238 - 21243
(2020/12/31)
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- One-pot Chemoenzymatic Deracemisation of Secondary Alcohols Employing Variants of Galactose Oxidase and Transfer Hydrogenation
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Enantiomerically enriched chiral secondary alcohols serve as valuable building blocks for drug intermediates and fine chemicals. In this study the deracemisation of secondary alcohols to generate enantiomeric pure chiral alcohols has been achieved by combining enantio-selective enzymatic oxidation of a secondary alcohol, by a variant of GOase (GOase M3-5), with either non-selective ketone reduction via transfer hydrogenation (TH) or enantio-selective asymmetric transfer hydrogenation (ATH). Both the enzymatic oxidation system and the transition-metal mediated reduction system were optimised to ensure compatibility with each other resulting in a homogeneous reaction system. 1-(4-nitrophenyl)ethanol was generated with 99 % conversion and 98 % ee by the deracemisation method, and it has been extended to a series of other secondary alcohols with comparable results.
- Yuan, Bo,Debecker, Damien P.,Wu, Xiaofeng,Xiao, Jianliang,Fei, Qiang,Turner, Nicholas J.
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p. 6191 - 6195
(2020/10/15)
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- Green synthesis of chiral aromatic alcohols with Lactobacillus kefiri P2 as a novel biocatalyst
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Biocatalytic reduction is a very important field of research in synthetic organic chemistry. Herein, three different Lactic Acid Bacteria (LAB) strains were evaluated for their bioreduction potential using acetophenone as a model substrate. Among these strains, Lactobacillus kefiri P2 strain was determined as the best asymmetric reduction biocatalyst. Reaction optimization parameters such as reaction time, temperature, agitation speed and pH were systematically optimized using Lactobacillus kefiri P2 strain and model substrate acetophenone. Under these optimized reaction conditions, secondary chiral alcohols were obtained by bioreduction of various prochiral ketones with results up to 99% enantiomeric excess. In addition, the steric and electronic effects of substituents on enantioselectivity and conversion were evaluated. It has been shown that Lactobacillus kefiri P2 biocatalyst was an effective catalyst for asymmetric reduction. This method provides an environmentally friendly method for the synthesis of optically pure alcohols and an alternative approach to chemical catalysts.
- Bayda?, Yasemin,Dertli, Enes,?ahin, Engin
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p. 1035 - 1045
(2020/03/03)
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- Cationic NHC-Phosphine Iridium Complexes: Highly Active Catalysts for Base-Free Hydrogenation of Ketones
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Novel bidentate N-heterocyclic carbene-phosphine iridium complexes have been synthesized and evaluated in the hydrogenation of ketones. Reported catalytic systems require base additives and, if excluded, need elevated temperature or high pressure of hydrogen gas to achieve satisfactory reactivity. The developed catalysts showed extremely high reactivity and good enantioselectivity under base-free and mild conditions. In the presence of 1 mol % catalyst under 1 bar hydrogen pressure at room temperature, hydrogenation was complete in 30 minutes giving up to 96 % ee. Again, this high reactivity was achieved in additive-free conditions. Mechanistic experiments demonstrated that balloon pressure of hydrogen was sufficient to form the activate species by reducing and eliminating the 1,5-cyclooctadiene ligand. The pre-activated catalyst was able to hydrogenate acetophenone with 89 % conversion in 5 min.
- Quan, Xu,Kerdphon, Sutthichat,Peters, Bram B. C.,Rujirawanich, Janjira,Krajangsri, Suppachai,Jongcharoenkamol, Jira,Andersson, Pher G.
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supporting information
p. 13311 - 13316
(2020/09/22)
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- Asymmetric Hydrogenation of Ketones and Enones with Chiral Lewis Base Derived Frustrated Lewis Pairs
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The concept of frustrated Lewis pairs (FLPs) has been widely applied in various research areas, and metal-free hydrogenation undoubtedly belongs to the most significant and successful ones. In the past decade, great efforts have been devoted to the synthesis of chiral boron Lewis acids. In a sharp contrast, chiral Lewis base derived FLPs have rarely been disclosed for the asymmetric hydrogenation. In this work, a novel type of chiral FLP was developed by simple combination of chiral oxazoline Lewis bases with achiral boron Lewis acids, thus providing a promising new direction for the development of chiral FLPs in the future. These chiral FLPs proved to be highly effective for the asymmetric hydrogenation of ketones, enones, and chromones, giving the corresponding products in high yields with up to 95 % ee. Mechanistic studies suggest that the hydrogen transfer to simple ketones likely proceeds in a concerted manner.
- Du, Haifeng,Feng, Xiangqing,Gao, Bochao,Meng, Wei
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supporting information
p. 4498 - 4504
(2020/02/05)
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- Optimisation, scope and advantages of the synthesis of chiral phenylethanols using whole seeds of Bauhinia variegata L. (Fabaceae) as a new and stereoselective bio-reducer of carbonyl compounds
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With the aim of finding new methods for environmentally friendly synthesis of chiral phenylethanols, a screening was carried out to identify seeds that could be used as a biocatalyst capable of reducing stereoselectively prochiral ketones. As a result, seeds of Bauhinia variegata L. (Fabaceae) were identified as being an efficient and stereoselective biological reducer of acetophenone to produce (S)-1-phenylethanol (conversion of 98% and 99 e.e.%). Then, to optimise the reductive process, the effects of some variables such as temperature, load of substrate, pH, co-solvent, and reuse and storability of the seeds as a function of time were established. Utilising the optimal reaction conditions, nineteen substituted acetophenones were reduced to their corresponding chiral alcohols with a conversion ranging from 30% to 98% and enantiomeric excess of between 65% and >99%, and in addition, useful key intermediates were also obtained by the synthesis of drugs. The scope and advantages of this new biocatalytic synthetic method are also discussed.Research highlights A screening was carried out to identify seeds that could be used as a biocatalyst Seeds of Bauhinia variegata have been identified as an efficient biocatalyst to reduce carbonyl compounds. Acetophenone and substituted acetophenones were reduced with high stereoselectivity. Some key intermediates were synthetised using this methodology. Seeds can be stored for twenty-four months without loss of activity.
- Aimar, Mario L.,Bordón, Daniela L.,Cantero, Juan J.,Decarlini, María F.,Demmel, Gabriela I.,Rossi, Laura I.,Ruiz, Gustavo M.,Vázquez, Ana M.
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- INHIBITORS OF CBL-B AND METHODS OF USE THEREOF
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Compounds, compositions, and methods for use in inhibiting the E3 enzyme Cbl-b in the ubiquitin proteasome pathway are disclosed. The compounds, compositions, and methods can be used to modulate the immune system, to treat diseases amenable to immune system modulation, and for treatment of cells in vivo, in vitro, or ex vivo.
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Paragraph 1383
(2019/08/12)
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- A comparative study on asymmetric reduction of ketones using the growing and resting cells of marine-derived fungi
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Whole-cell biocatalysts offer a highly enantioselective, minimally polluting route to optically active alcohols. Currently, most of the whole-cell catalytic performance involves resting cells rather than growing cell biotransformation, which is one-step process that benefits from the simultaneous growth and biotransformation, eliminating the need for catalysts preparation. In this paper, asymmetric reduction of 14 aromatic ketones to the corresponding enantiomerically pure alcohols was successfully conducted using the growing and resting cells of marine-derived fungi under optimized conditions. Good yields and excellent enantioselectivities were achieved with both methods. Although substrate inhibition might be a limiting factor for growing cell biotransformation, the selected strain can still completely convert 10-mM substrates into the desired products. The resting cell biotransformation showed a capacity to be recycled nine times without a significant decrease in the activity. This is the first study to perform asymmetric reduction of ketones by one-step growing cell biotransformation.
- Liu, Hui,Chen, Bi-Shuang,Ribeiro de Souza, Fayene Zeferino,Liu, Lan
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- N,O- vs N,C-Chelation in Half-Sandwich Iridium Complexes: A Dramatic Effect on Enantioselectivity in Asymmetric Transfer Hydrogenation of Ketones
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Cyclometalation of [Cp?IrCl2]2 with methyl (S)-2-phenyl-4,5-dihydrooxazole-4-carboxylate in the presence of NaOAc selectively led to a N,C- or N,O-chelated Cp?Ir(III) complex, depending on whether or not water was present in the reaction. While derived from the same precursor, these two complexes behaved in a dramatically different manner in asymmetric transfer hydrogenation (ATH) of ketones by formic acid, with the N,O-chelated complex being much more selective and active. The sense of asymmetric induction is also different, with the N,O-complex affording S while the N,C-analogue R alcohols. Further study revealed that the nature of the base additive considerably impacts the enantioselectivity and the effective HCOOH/amine ratios. These observations show the importance of ligand coordination mode and using the right base for ATH reactions.
- Zhou, Gang,Aboo, Ahmed H.,Robertson, Craig M.,Liu, Ruixia,Li, Zhenhua,Luzyanin, Konstantin,Berry, Neil G.,Chen, Weiping,Xiao, Jianliang
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p. 8020 - 8026
(2018/09/06)
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- Extreme halophilic alcohol dehydrogenase mediated highly efficient syntheses of enantiopure aromatic alcohols
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Enzymatic synthesis of enantiopure aromatic secondary alcohols (including substituted, hetero-aromatic and bicyclic structures) was carried out using halophilic alcohol dehydrogenase ADH2 from Haloferax volcanii (HvADH2). This enzyme showed an unprecedented substrate scope and absolute enatioselectivity. The cofactor NADPH was used catalytically and regenerated in situ by the biocatalyst, in the presence of 5% ethanol. The efficiency of HvADH2 for the conversion of aromatic ketones was markedly influenced by the steric and electronic factors as well as the solubility of ketones in the reaction medium. Furthermore, carbonyl stretching band frequencies ν (CO) have been measured for different ketones to understand the effect of electron withdrawing or donating properties of the ketone substituents on the reaction rate catalyzed by HvADH2. Good correlation was observed between ν (CO) of methyl aryl-ketones and the reaction rate catalyzed by HvADH2. The enzyme catalyzed the reductions of ketone substrates on the preparative scale, demonstrating that HvADH2 would be a valuable biocatalyst for the preparation of chiral aromatic alcohols of pharmaceutical interest.
- Alsafadi, Diya,Alsalman, Safaa,Paradisi, Francesca
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p. 9169 - 9175
(2017/11/15)
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- Zinc-Catalyzed Enantioselective Hydrosilylation of Ketones and Imines under Solvent-Free Conditions
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The zinc acetate promoted asymmetric hydrosilylation of various ketones and imines under solvent-free conditions was examined by using an unprecedented low catalyst loading. Exposure of ketones to 0.05 mol % Zn-based chiral diamine complex in the presence of triethoxysilane afforded enantioenriched alcohols in excellent yields (up to 98 %) and enantioselectivities (up to 97 % ee). This methodology also allowed for the chemoselective 1,2-reduction of α,β-unsaturated ketones and imines.
- Szewczyk, Marcin,Bez?ada, Agata,Mlynarski, Jacek
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p. 3575 - 3579
(2016/12/14)
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- Enzymatic reduction of acetophenone derivatives with a benzil reductase from Pichia glucozyma (KRED1-Pglu): electronic and steric effects on activity and enantioselectivity
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A recombinant ketoreductase from Pichia glucozyma (KRED1-Pglu) was used for the enantioselective reduction of various mono-substituted acetophenones. Reaction rates of meta- and para-derivatives were consistent with the electronic effects described by σ-Hammett coefficients; on the other hand, enantioselectivity was determined by an opposite orientation of the substrate in the binding pocket. Reduction of ortho-derivatives occurred only with substrates bearing substituents with low steric impact (i.e., F and CN). Reactivity was controlled by stereoelectronic features (C=O length and charge, shape of LUMO frontier molecular orbitals), which can be theoretically calculated.
- Contente, Martina L.,Serra, Immacolata,Palazzolo, Luca,Parravicini, Chiara,Gianazza, Elisabetta,Eberini, Ivano,Pinto, Andrea,Guidi, Benedetta,Molinari, Francesco,Romano, Diego
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supporting information
p. 3404 - 3408
(2016/04/09)
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- Synthesis of enantiopure epoxide by 'one pot' chemoenzymatic approach using a highly enantioselective dehydrogenase
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Enantiopure α-phenethyl alcohols, including aromatic halohydrins, are important chiral building blocks. One of the best approaches to synthesise α-phenethyl alcohols is asymmetric reduction of prochiral ketones by alcohol dehydrogenases (ADHs). The obtained enantiopure halohydrin could be directly used to produce enantiopure epoxide through a base-induced ring-closure reaction, which is an attractive 'one pot' chemoenzymatic method for producing high-yield epoxide. In this study, a novel medium-chain dehydrogenase (KcDH) from Kuraishia capsulate CBS1993 was identified and characterised to show its broad substrate scope and excellent enantioselectivity. KcDH showed activities on 25 substrates of the 26 tested aromatic ketones and heteroaryl ketones, with an enantiomeric excess (ee) >99% and the highest relative activity observed with para-nitro acetophenone. Due to its high enantioselectivity for α-haloketones, a chemoenzymatic method for the synthesis of enantiopure styrene oxide (SO) and phenyl glycidyl ether (PGE) was developed through a base-induced ring-closure reaction on enantiopure halohydrin obtained with KcDH. (R)-SO and (S)-PGE were obtained in 86% and 94% analytical yield, respectively, and both epoxides were obtained with ee >99%. Thus, our results suggested that KcDH may be a promising biocatalyst for the production of multiple enantiopure α-phenethyl alcohols and epoxides.
- Wu, Kai,Chen, Lifeng,Fan, Haiyang,Zhao, Zhiqiang,Wang, Hualei,Wei, Dongzhi
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p. 899 - 904
(2016/02/05)
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- Zinc Acetate-Catalyzed Enantioselective Hydrosilylation of Ketones
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Zinc acetate complexes with a chiral diphenylethylenediamine (DPEDA)-derived ligand have been proved to be efficient catalysts for the enantioselective hydrosilylation of aryl ketones. Replacing pyrophoric dialkylzinc with the readily available zinc salt simplifies the procedures and provides excellent conversions (up to >99%) and enantioselectivities (ees up to 97%).
- Szewczyk, Marcin,Stanek, Filip,Bez?ada, Agata,Mlynarski, Jacek
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supporting information
p. 3727 - 3731
(2016/01/25)
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- Half-sandwich Ru(η6-C6H6) complexes with chiral aroylthioureas for enhanced asymmetric transfer hydrogenation of ketones-experimental and theoretical studies
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The reactions of [RuCl2(η6-C6H6)]2 with chiral aroylthiourea ligands yielded pseudo-octahedral half-sandwich "piano-stool" complexes. All the Ru(ii) complexes were characterized by analytical and spectral (UV-visible, FT-IR, 1H NMR and 13C NMR) studies. The molecular structures of the ligands (L2 and L4) and the complexes (2, 4 and 5) were confirmed by single crystal XRD. All the complexes were successfully screened as catalysts for the asymmetric transfer hydrogenation (ATH) of ketones using 2-propanol as the hydrogen source in the presence of KOH. The ATH reactions proceeded with excellent yields (up to 99%) and very good enantioselectivity (up to 99% ee). The scope of the present catalytic system was extended to substituted aromatic ketones and few hetero-aromatic ketones. Density functional theory (DFT) calculations predicted non-classical, concerted transition states for the ATH reactions. The catalytic activity of Ru-benzene complexes toward asymmetric reduction of ketones was significantly higher compared to that of p-cymene complex analogues. Such enhanced efficiency and product selectivity of Ru-benzene complexes compared to those of Ru-p-cymene complexes were rationalized by the computational study.
- Mary Sheeba, Mani,Preethi, Sankaranarayanan,Nijamudheen,Muthu Tamizh, Manoharan,Datta, Ayan,Farrugia, Louis J.,Karvembu, Ramasamy
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p. 4790 - 4799
(2015/10/05)
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- Asymmetric hydrosilylation of ketones catalyzed by zinc acetate with hindered pybox ligands
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A highly efficient asymmetric hydrosilylation (AHS) of a wide variety of prochiral aryl ketones catalyzed by zinc acetate with TPS-he-pybox (tert-butyldiphenylsilyl hydroxyethyl pybox) ligand has been successfully developed. Cheap and readily available chiral Lewis acids based on zinc salts have been used as promising catalyst for the reduction of aryl ketones under mild conditions at room temperature leading to chiral alcohols in excellent yields and good to high enantioselectivities (up to 85% ee).
- Lowicki, Daniel,Bezlada, Agata,Mlynarski, Jacek
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supporting information
p. 591 - 595
(2014/05/20)
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- Mesoporous silica KIT-6 supported superparamagnetic CuFe2O 4 nanoparticles for catalytic asymmetric hydrosilylation of ketones in air
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A diverse range of prochiral ketones were reduced in air with high yields and good-to-excellent enantioselectivities (up to 97% ee) in the presence of a heterogeneous catalyst system, which was in situ formed from catalytic amounts of superparamagnetic CuFe2O4 nanoparticles supported on mesoporous silica KIT-6 and non-racemic dipyridylphosphine ligand, the stoichiometric hydride donor polymethylhydrosiloxane (PMHS) as well as certain amounts of additives. The magnetically separable catalysts could be efficiently reused 4 times without apparent loss of both the activity and enantioselectivity. the Partner Organisations 2014.
- Li, Min,Li, Bin,Xia, Hong-Feng,Ye, Danru,Wu, Jing,Shi, Yifeng
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p. 2680 - 2688
(2014/05/06)
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- Synthesis and catalytic applications of an extended range of tethered ruthenium(II)/η6-arene/diamine complexes
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A series of novel enantiopure Ru(II) complexes containing a chiral diamine and η6-arene connected by a tethering group have been prepared and were evaluated in the asymmetric reductions of a range of ketones. Changes to the level of steric hindrance and the addition of an electron-withdrawing functionality on the sulfonyl group have a significant effect on the reactivity and enantioselectivity of the catalysts.
- Hodgkinson, Roy,Jurk, Vclav,Zanotti-Gerosa, Antonio,Nedden, Hans Günter,Blackaby, Andrew,Clarkson, Guy J.,Wills, Martin
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supporting information
p. 5517 - 5524
(2015/02/19)
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- Fruits of the glossy privet (Ligustrum lucidum-Oleaceae) as biocatalysts for producing chiral aromatic alcohols
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The screening of four invasive plant species for use as biocatalysts in the stereoselective reduction of ketones is reported. Our studies revealed that fruits of Ligustrum lucidum can be used for the bioreduction of acetophenone to (S)-1-phenylethanol (94% conversion, >99 enantiomeric excess [ee]%). Using this methodology, 13 substituted (S)-phenylethanols were synthesized with good ee values (>99.9 to 78%) using a technique which is more environmentally friendly than classical reduction of prochiral ketones. The results reveal the fruits of L. lucidum to be promising biocatalysts for the production of key intermediates.
- Aimar, Mario L.,BordN, Daniela L.,Formica, Stella M.,Cantero, Juan J.,Vazquez, Ana M.,Velasco, Manuel I.,Rossi, Laura I.
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p. 348 - 357
(2015/02/19)
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- Phosphonate-containing polystyrene copolymer-supported Ru catalyst for asymmetric transfer hydrogenation in water
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A series of phosphonate-containing copolystyrenes with chiral ligand (1R,2R)-(+)-N1-toluenesulfonyl-1,2-diphenylethylene-1,2-diamine were prepared by radical copolymerization. The supported Ru catalysts with excellent catalytic performances (94-98% yields, 93.9-97.8% ee and 100% chemoselectivity) in aqueous asymmetric transfer hydrogenation could be easily recycled by centrifugal separation.
- Xu, Xiao,Wang, Rui,Wan, Jingwei,Ma, Xuebing,Peng, Jingdong
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p. 6747 - 6751
(2013/06/04)
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- Chirally functionalized SBA-15 as efficient heterogeneous catalyst for asymmetric ketone reduction
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Chiral amine catalyst was synthesized using (1R, 2S)-(-)-norephedrine and 5-chlorosalicylaldehyde by reductive amination. The structure of the catalyst was confirmed using 1H-NMR and 13C-NMR spectroscopic method. The catalyst was immobilized onto SBA-15 via covalent bonding using 3-chloropropyltrimethoxysilane as a reactive surface modifier under reflux condition using toluene as a solvent. The supported chiral catalyst was characterized using various physico-chemical techniques like XRD, SEM, N 2 adsorption isotherm, FTIR and UV-DRS to study the morphology, pore dimension, functional group analysis and catalyst loading in the mesoporous material. The immobilized catalyst was studied for prochiral ketone reduction using 30 mol% of chiral catalyst and boranedimethylsulphide as a stoichiometric reductant in toluene under inert atmosphere for 30 minutes. Secondary alcohols were formed up to 79% enantiomeric excess for selective ketones. Catalyst was recycled from the reaction mixture and used for further reaction without much effect on the catalytic conversion. Copyright
- Balakrishnan, Umesh,Velmathi, Sivan
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p. 3079 - 3086
(2013/08/25)
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- Exploiting the enzymatic machinery of Arthrobacter atrocyaneus for oxidative kinetic resolution of secondary alcohols
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We evaluated Arthrobacter atrocyaneus (R1AF57) as producer of oxidoreductases for oxidative kinetic resolution of racemic secondary alcohols via oxidation reaction. This bacterium was isolated from Amazon soil samples using medium enriched with (RS)-1-(4-methylphenyl)ethanol as a carbon source. The kinetic resolution of several secondary alcohols through enantioselective oxidation mediated by resting cells and growing cells of A. atrocyaneus was efficiently achieved for the most alcohols. In general, it was possible to obtain only the (S)-enantiomer from (RS)-1-arylethanols.
- Silva, Camila R.,Souza, Juliana C.,Araujo, Lidiane S.,Kagohara, Edna,Garcia, Thais P.,Pelizzari, Vivian H.,Andrade, Leandro H.
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- Enantioselective zinc-catalyzed hydrosilylation of ketones using pybox or pybim ligands
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The combination of ZnEt2 and chiral pyridinebisoxazoline (pybox) or pyridinebisimidazoline (pybim) ligands catalyzed the asymmetric hydrosilylation of aryl, alkyl, cyclic, heterocyclic, and aliphatic ketones. Under mild conditions, high yields and good enantioselectivities were achieved. ESI measurements allowed for the characterization of the active catalyst. Zincing outside of the pybox: A ZnEt2/pybox catalyst promotes the hydrosilylation of carbonyl compounds under mild conditions to afford high yields and good ee values for a broad range of aryl, alkyl, cyclic, heterocyclic, and aliphatic ketones.
- Junge, Kathrin,Moeller, Konstanze,Wendt, Bianca,Das, Shoubhik,Goerdes, Dirk,Thurow, Kerstin,Beller, Matthias
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experimental part
p. 314 - 320
(2012/04/18)
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- Varying the ratio of formic acid to triethylamine impacts on asymmetric transfer hydrogenation of ketones
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Asymmetric transfer hydrogenation (ATH) is frequently carried out in the azeotropic mixture of formic acid (F) and triethylamine (T), where the F/T molar ratio is 2.5. This study shows that the F/T ratio affects both the reduction rate and enantioselectivity, with the optimum ratio being 0.2 in the ATH of ketones with the Ru-TsDPEN catalyst. Under such conditions, a range of substrates have been reduced, affording high yields and good to excellent enantioselectivities. In comparison with the common azeotropic F-T system, the reduction is faster. This protocol improves both the classic azeotropic and the aqueous-formate system when using water-insoluble ketones.
- Zhou, Xiaowei,Wu, Xiaofeng,Yang, Bolun,Xiao, Jianliang
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experimental part
p. 133 - 140
(2012/05/20)
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- α-Amino-oximes based on optically pure limonene: A new ligands family for ruthenium-catalyzed asymmetric transfer hydrogenation
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A new family of bifunctional, optically pure α-amino-oxime ligands based on (R)-limonene has been synthesized and used as chiral inducers for enantioselective hydrogen transfer reactions on various ketones in the presence of ruthenium catalysts. The X-ray
- Ibn El Alami, Mohammed Samir,El Amrani, Mohamed Amin,Dahdouh, Abdelaziz,Roussel, Pascal,Suisse, Isabelle,Mortreux, Andre
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experimental part
p. 675 - 682
(2012/09/22)
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- Asymmetric reduction of acetophenone derivatives by Lens culinaris
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The enzymatic reduction of acetophenone derivatives has been evaluated using whole cells from the edible plant lentil (Lens culinaris) as biocatalyst to afford chiral (R) and (S)-alcohols in enantiomeric excess 68-99%. Acetophenone was selected as the model substrate for enantioselective bioreduction. The reaction was performed under a range of conditions in order to optimize the bioreduction procedure with respect to reaction time, media and optimal mass of lentil. With substituted (fluorine, chlorine, bromine, methyl, hydroxyl, methoxy, amino and nitro groups) acetophenones, electronic and steric influences on the course of the reaction were observed.
- Ferreira, Daniele Alves,Da Costa Assun??o, Jo?o Carlos,De Lemos, Telma Leda Gomes,Monte, Francisco José Queiroz
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p. 469 - 475
(2013/02/23)
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- A tandem and fully enzymatic procedure for the green resolution of chiral alcohols: Acylation and deacylation in non-aqueous media
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A green and fully enzymatic procedure for the resolution of chiral alcohols through lipase/esterase-catalyzed acylation and subsequent lipase-catalyzed aminolysis using anhydrous ammonia was demonstrated. Both enantiomers can be obtained in high ee values (up to >99%) under ambient reaction conditions. The solvent and acyl donors can be recycled, and the enzyme can be reused for up to five times.
- Wang, Bo,Jiang, Ling,Wang, Jue,Ma, Jingbo,Liu, Min,Yu, Hongwei
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experimental part
p. 980 - 985
(2011/10/04)
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- First example of hydrolytic kinetic resolution of acrylate of secondary alcohols by lipase Amano AK
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Lipase Amano AK is found to be extremely efficient catalyst for hydrolytic kinetic resolution of acrylates of secondary alcohols in aqueous phosphate buffer at pH 7.0. Both aliphatic and benzylic secondary alcohols show good to excellent E values.
- Bora, Pranjal P.,Bez, Ghanashyam,Anal, Jasha Momo H.
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p. 270 - 275
(2012/07/03)
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- Cobalt(II)-catalyzed asymmetric hydrosilylation of simple ketones using dipyridylphosphine ligands in air
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In the presence of PhSiH3 as the hydride donor, catalytic amounts of non-racemic dipyridylphosphine and an easy-to-handle cobalt salt Co(OAc)2·4H2O formed in situ an effective catalyst system for the asymmetric reduction o
- Yu, Feng,Zhang, Xi-Chang,Wu, Fei-Fei,Zhou, Ji-Ning,Fang, Wenjun,Wu, Jing,Chan, Albert S. C.
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supporting information; experimental part
p. 5652 - 5654
(2011/09/15)
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- Copper-dipyridylphosphine-polymethylhydrosiloxane: A practical and effective system for the asymmetric catalytic hydrosilylation of ketones
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In the presence of the inexpensive and non-toxic stoichiometric reductant polymethylhydrosiloxane (PMHS), the chiral copper(II)-dipyridylphosphine catalyst displayed high efficiency in the stereoselective hydrosilylation of a wide scope of aryl alkyl and heteroaromatic ketones under an air atmosphere and mild conditions in good to excellent ees (up to 97%). With certain amounts of sodium tert-butoxide and tert-butyl alcohol as additives, the reaction on a 21-g substrate scale can be conveniently completed within a few hours even at a substrate-to-ligand (S/L) ratio of 50,000. Copyright
- Zhang, Xi-Chang,Wu, Fei-Fei,Li, Shijun,Zhou, Ji-Ning,Wu, Jing,Li, Ning,Fang, Wenjun,Lam, Kim Hung,Chan, Albert S. C.
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supporting information; experimental part
p. 1457 - 1462
(2011/08/03)
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- Copper(II)-catalyzed hydrosilylation of ketones using chiral dipyridylphosphane ligands: Highly enantioselective synthesis of valuable alcohols
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In the presence of PhSiH3 as the reductant, the combination of enantiomeric dipyridylphosphane ligands and Cu(OAc)2·H 2O, which is an easy-to-handle and inexpensive copper salt, led to a remarkably practical and versatile chiral catalyst system. The stereoselective formation of a selection of synthetically interesting β-, γ- or δ-halo alcohols bearing high degrees of enantiopurity (up to 99.9 % enantiomeric excess (ee)) was realized with a substrate-to-ligand molar ratio (S/L) of up to 10 000. The present protocol also allowed the hydrosilylation of a diverse spectrum of alkyl aryl ketones with excellent enantioselectivities (up to 98 % ee) and exceedingly high turn-over rates (up to 50 000 S/L molar ratio in 50 min reaction time) in air, under very mild conditions, which offers great opportunities for the preparation of various physiologically active targets. The synthetic utility of the chiral products obtained was highlighted by the efficient conversion of optically enriched β-halo alcohols into the corresponding styrene oxide, β-amino alcohol, and β-azido alcohol, respectively.
- Yu, Feng,Zhou, Ji-Ning,Zhang, Xi-Chang,Sui, Yao-Zong,Wu, Fei-Fei,Xie, Lin-Jie,S. C. Chan, Albert,Wu, Jing
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scheme or table
p. 14234 - 14240
(2012/01/12)
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- Asymmetric transfer hydrogenation of prochiral ketones in aqueous media with chiral water-soluble and heterogenized bifunctional catalysts of the RhCp*-type ligand
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Asymmetric transfer hydrogenation (ATH) of prochiral aromatic ketones was carried out with a water-soluble complex of RhIIICp* and mononitrobenzenesulfonamide bidentate ligand (1R,2R)-N-(2-aminocyclohexyl)-4- nitrobenzenesulfonamide 1 derived from chiral cyclohexane-1,2-diamine. Aqueous sodium formate was used as the hydride source. The reaction afforded the chiral alcohols in good enantioselectivities (79-93%) and yields (>99%). The modified monosulfonamide ligand was also covalently immobilized on solid phase such as silica, resin, and mesoporous SBA-15 silica and then explored as a catalyst with RhIIICp* in the ATH of acetophenone. Copyright
- Barron-Jaime, Angelica,Narvaez-Garayzar, Oscar F.,Gonzalez, Jorge,Ibarra-Galvan, Valentin,Aguirre, Gerardo,Parra-Hake, Miguel,Chavez, Daniel,Somanathan, Ratnasamy
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experimental part
p. 178 - 184
(2011/11/06)
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- Escherichia coli BioH: A highly enantioselective and organic solvent tolerant esterase for kinetic resolution of sec-alcohols
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Escherichia coli BioH, which is obligatory for biotin synthesis, was found to be an organic solvent tolerant esterase with high enantioselectivity for the kinetic resolution of sec-alcohols using free enzyme powder. With this esterase, a variety of racemic sec-alcohols were efficiently resolved with ee values of up to 99%.
- Wang, Bo,Tang, Xiaoling,Liu, Ji,Yu, Hongwei
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supporting information; experimental part
p. 6360 - 6364
(2011/01/04)
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- Reduction processes biocatalyzed by Vigna unguiculata
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Whole cells from the Brazilian beans feijao de corda (Vigna unguiculata) have been employed as biocatalysts in different bioreduction processes. Good to excellent selectivities can be obtained in the reduction of aromatic and aliphatic ketones, as well as β-ketoesters, depending on the conversions and the chemoselectivity on the substrate structure. This biocatalyst was also able to reduce the nitro moiety of different aromatic nitro compounds, showing as well enoate reductase activity, and chemoselectively catalyzing the double bond reduction of 4-phenyl-3-buten-2-one with moderate conversion.
- Bizerra, Ayla M.C.,Gonzalo, Gonzalo de,Lavandera, Ivan,Gotor-Fernandez, Vicente,de Mattos, Marcos Carlos,de Oliveira, Maria da Conceicao F.,Lemos, Telma L.G.,Gotor, Vicente
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experimental part
p. 566 - 570
(2010/08/06)
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- ASYMMETRIC CATALYST AND PROCESS FOR PREPARING OPTICALLY ACTIVE ALCOHOLS USING THE SAME
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The present invention provides an organic metal compound, a ligand, an asymmetric catalyst, and a process for preparing optically-active alcohols using the asymmetric catalyst. The organic metal compound of the present invention is expressed by the follow
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Page/Page column 88; 95
(2010/11/03)
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- New class of β-aminoalcohol ligands derived from isosorbide and isomannide: Application in hydrogen transfer reduction of prochiral ketones
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Starting from isosorbide and isomannide, two by-products from the starch industry, a family of chiral functionalized β-aminoalcohols presenting a THF ring has been synthesized as potential ligands for hydrogen transfer reduction of prochiral ketones. Unde
- Le, Tin Thanh,Guillarme, Stéphane,Saluzzo, Christine
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experimental part
p. 8893 - 8898
(2011/01/04)
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- Lentinus strigellus: a new versatile stereoselective biocatalyst for the bioreduction of prochiral ketones
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Growing cells of the basiodiomycete Lentinus strigellus in potato-dextrose broth have been used for the first time as a biocatalyst in the stereoselective reduction of aromatic and aliphatic ketones. Most of the aromatic ketones were converted into the corresponding optically active alcohols in up to >99% enantiomeric excess under very mild reaction conditions. Among the aliphatic ketones tested, 2-octanone was enzymatically reduced by this microorganism to enantiopure (S)-2-octanol with almost complete conversion.
- Barros-Filho, Bartholomeu A.,de Oliveira, Maria da Conceicao F.,Lemos, Telma L.G.,de Mattos, Marcos C.,Gonzalo, Gonzalo de,Gotor-Fernandez, Vicente,Gotor, Vicente
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experimental part
p. 1057 - 1061
(2009/10/02)
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