- Highly Active Cooperative Lewis Acid—Ammonium Salt Catalyst for the Enantioselective Hydroboration of Ketones
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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
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supporting information
p. 5544 - 5553
(2021/02/05)
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- London Dispersion Interactions Rather than Steric Hindrance Determine the Enantioselectivity of the Corey–Bakshi–Shibata Reduction
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The well-known Corey–Bakshi–Shibata (CBS) reduction is a powerful method for the asymmetric synthesis of alcohols from prochiral ketones, often featuring high yields and excellent selectivities. While steric repulsion has been regarded as the key director of the observed high enantioselectivity for many years, we show that London dispersion (LD) interactions are at least as important for enantiodiscrimination. We exemplify this through a combination of detailed computational and experimental studies for a series of modified CBS catalysts equipped with dispersion energy donors (DEDs) in the catalysts and the substrates. Our results demonstrate that attractive LD interactions between the catalyst and the substrate, rather than steric repulsion, determine the selectivity. As a key outcome of our study, we were able to improve the catalyst design for some challenging CBS reductions.
- Eschmann, Christian,Song, Lijuan,Schreiner, Peter R.
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p. 4823 - 4832
(2021/02/01)
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- Substrate Analogues for the Enzyme-Catalyzed Detoxification of the Organophosphate Nerve Agents—Sarin, Soman, and Cyclosarin
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The G-type nerve agents, sarin (GB), soman (GD), and cyclosarin (GF), are among the most toxic compounds known. Much progress has been made in evolving the enzyme phosphotriesterase (PTE) fromPseudomonas diminutafor the decontamination of the G-agents; however, the extreme toxicity of the G-agents makes the use of substrate analogues necessary. Typical analogues utilize a chromogenic leaving group to facilitate high-throughput screening, and substitution of anO-methyl for theP-methyl group found in the G-agents, in an effort to reduce toxicity. Till date, there has been no systematic evaluation of the effects of these substitutions on catalytic activity, and the presumed reduction in toxicity has not been tested. A series of 21 G-agent analogues, including all combinations ofO-methyl,p-nitrophenyl, and thiophosphate substitutions, have been synthesized and evaluated for their ability to unveil the stereoselectivity and catalytic activity of PTE variants against the authentic G-type nerve agents. The potential toxicity of these analogues was evaluated by measuring the rate of inactivation of acetylcholinesterase (AChE). All of the substitutions reduced inactivation of AChE by more than 100-fold, with the most effective being the thiophosphate analogues, which reduced the rate of inactivation by about 4-5 orders of magnitude. The analogues were found to reliably predict changes in catalytic activity and stereoselectivity of the PTE variants and led to the identification of the BHR-30 variant, which has no apparent stereoselectivity against GD and akcat/Kmof 1.4 × 106, making it the most efficient enzyme for GD decontamination reported till date.
- Bigley, Andrew N.,Harvey, Steven P.,Narindoshvili, Tamari,Raushel, Frank M.
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p. 2875 - 2887
(2021/10/01)
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- Chiral Imidazo[1,5- a]pyridine-Oxazolines: A Versatile Family of NHC Ligands for the Highly Enantioselective Hydrosilylation of Ketones
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Herein we report the synthesis and application of a versatile class of N-heterocyclic carbene ligands based on an imidazo[1,5-a]pyridine-3-ylidine backbone that is fused to a chiral oxazoline auxiliary. The key step in the synthesis of these ligands involves the installation of the oxazoline functionality via a microwave-assisted condensation of a cyano-azolium salt with a wide variety of 2-amino alcohols. The resulting chiral bidentate NHC-oxazoline ligands form stable complexes with rhodium(I) that are efficient catalysts for the enantioselective hydrosilylation of structurally diverse ketones. The corresponding secondary alcohols are isolated in good yields (typically >90%) with good to excellent enantioselectivities (80-93% ee). The reported hydrosilylation occurs at ambient temperatures (40 °C), with excellent functional group tolerability. Even ketones bearing heterocyclic substituents (e.g., pyridine or thiophene) or complex organic architectures are hydrosilylated efficiently, which is discussed further in this report.
- Chinna Ayya Swamy,Varenikov, Andrii,Ruiter, Graham De
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supporting information
p. 247 - 257
(2020/02/04)
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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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p. 820 - 830
(2018/12/13)
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- Enantioselective Hydrogenation of Ketones using Different Metal Complexes with a Chiral PNP Pincer Ligand
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The synthesis of different metal pincer complexes coordinating to the chiral PNP ligand bis(2-((2R,5R)-2,5-dimethyl-phospholanoethyl))amine is described in detail. The characterized complexes with Mn, Fe, Re and Ru as metal centers showed good activities regarding the reduction of several prochiral ketones. Comparing these catalysts, the non-noble metal complexes produced best selectivities not only for aromatic substrates, but also for different kinds of aliphatic ones leading to enantioselectivities up to 99% ee. Theoretical investigations elucidated the mechanism and rationalized the selectivity. (Figure presented.).
- Garbe, Marcel,Wei, Zhihong,Tannert, Bianca,Spannenberg, Anke,Jiao, Haijun,Bachmann, Stephan,Scalone, Michelangelo,Junge, Kathrin,Beller, Matthias
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supporting information
p. 1913 - 1920
(2019/03/13)
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- Iridium and Rhodium Complexes Containing Enantiopure Primary Amine-Tethered N-Heterocyclic Carbenes: Synthesis, Characterization, Reactivity, and Catalytic Asymmetric Hydrogenation of Ketones
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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.
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supporting information
p. 491 - 504
(2018/02/17)
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- CHIRAL METAL COMPLEX COMPOUNDS
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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; 23; 24; 26; 27
(2018/11/10)
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- Iridium-Catalyzed Asymmetric Hydrogenation of Ketones with Accessible and Modular Ferrocene-Based Amino-phosphine Acid (f-Ampha) Ligands
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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
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supporting information
p. 690 - 693
(2017/02/10)
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- Enantioselective Transfer Hydrogenation of Ketones Catalyzed by a Manganese Complex Containing an Unsymmetrical Chiral PNP′ Tridentate Ligand
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Manganese complexes of the types [Mn(PNP′)(Br)(CO)2] and [Mn(PNP′)(H)(CO)2] containing a tridentate ligand with a planar chiral ferrocene and a centro chiral aliphatic unit were synthesized, characterized, and tested in the enantiose
- Zirakzadeh, Afrooz,de Aguiar, Sara R. M. M.,St?ger, Berthold,Widhalm, Michael,Kirchner, Karl
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p. 1744 - 1748
(2017/05/29)
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- Catalytic Asymmetric Addition of Organolithium Reagents to Aldehydes
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Herein we report an efficient catalytic system for the titanium-promoted enantioselective addition of organolithium reagents to aldehydes, based on chiral Ar-BINMOL ligands. Unprecedented yields and enantioselectivities are achieved in the alkylation reactions of aliphatic aldehydes. Remarkably, methyllithium can be added to a wide variety of aromatic and aliphatic aldehydes, providing versatile chiral methyl carbinol units in a simple one-pot procedure under mild conditions and in very short reaction times.
- Veguillas, Marcos,Solà, Ricard,Shaw, Luke,Maciá, Beatriz
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p. 1788 - 1794
(2016/04/05)
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- Enantioselective borane reduction of ketones catalyzed by tricyclic 1,3,2-oxazaborolidines
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Two novel tricyclic 1,3,2-oxazaborolidines were synthesized in seven steps from methyl Boc-l-pyroglutamate. They are characterized by an ortho- and peri-fused 5/5/6-ring system with the B-N bond forming one ring junction. In the asymmetric borane reduction of ketones, the B-alkoxy bridged derivative permits excellent enantioselectivities of up to 98% ee and its activity is comparable to that of the standard CBS catalyst. The closely related, B-alkyl bridged derivative is less enantioselective and less active, as determined by competition experiments.
- Kaldun, Johannes,Krimalowski, Alexander,Breuning, Matthias
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supporting information
p. 2492 - 2495
(2016/05/24)
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- Iron cyclopentadienone complexes derived from C2-symmetric bis-propargylic alcohols; Preparation and applications to catalysis
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A series of complexes containing the iron-cyclopentadienone structure were prepared by cyclising bis-propargylic alcohols and their derivatives with iron pentacarbonyl. The resulting complexes were characterised and tested in the catalysis of ketone reduction and alcohol oxidation. The complexes are competent catalysts for ketone reduction and alcohol oxidations.
- Hodgkinson, Roy,Del Grosso, Alessandro,Clarkson, Guy,Wills, Martin
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supporting information
p. 3992 - 4005
(2016/03/05)
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- Development of an axially chiral sp3P/sp3NH/sp2N-combined linear tridentate ligand - Fac-selective formation of Ru(II) complexes and application to ketone hydrogenation
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A newly developed chiral linear tridentate ligand, R-PN(H)N (R=H or Ph), possesses Ph2P and PyCH2NH groups at C(2) and C(2′) positions of the 1,1′-binaphthyl skeleton without or with a C(3)-Ph substituent. The steric effect of C(3)-Ph and the electronic effect of the DMSO co-ligand realize the facial selective generation of fac-RuCl2(Ph-PN(H)N)(dmso) and fac-[Ru(H-PN(H)N)(dmso)3](BF4)2, respectively. Both an H-Ru?sp3N-H reaction site responsible for the donor-acceptor bifunctional catalyst (DACat) and a fence/plane chiral context were constructed by means of the following advantageous points: i) the sp3P, sp3N, and sp2N ligating atoms have different electronic properties; ii) DMSO trans to sp3N strongly coordinates to Ru and is fixed by a PyC(6)H?O=S hydrogen bond; and iii) the single NH function simplifies the DACat reaction site. The synergistic effect has led to success in the asymmetric hydrogenation of sterically demanding ketones. Structural characteristics of first-row transition metal complexes of R-PN(H)N have been also investigated.
- Yamamura, Tomoya,Nakane, Satoshi,Nomura, Yuko,Tanaka, Shinji,Kitamura, Masato
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supporting information
p. 3781 - 3789
(2016/06/06)
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- Synthesis of aminomethyl quinazoline based ruthenium (II) complex and its application in asymmetric transfer hydrogenation under mild conditions
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The new chiral aminomethyl quinazoline (amq) type ligand derived from L-phenylalanine was synthesized and coordinated with [RuCl2(PPh3)dppb] to obtain ruthenium(II) complex. This catalyst displayed considerable reactivity (up to 97% ee and 99% conversion) in the asymmetric transfer hydrogenation of ketones using 2-propanol as a hydrogen source in the presence of NaOiPr.
- Agac, Ahmet,Karakaya, Idris,Sahin, Irfan,Emir, Sedat,Karabuga, Semistan,Ulukanli, Sabri
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p. 189 - 193
(2016/07/25)
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- Catalytic enantioselective addition of methyltriisopropoxititanium to aldehydes
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An efficient catalyst for the enantioselective synthesis of chiral methyl carbinols from aldehydes is presented. The system uses methyltriisopropoxytitanium as a nucleophile and a readily available binaphthyl derivative as a chiral ligand. The enantioselective methylation of both aromatic and aliphatic aldehydes proceeds with good yields and high enantioselectivities under mild conditions.
- Veguillas, Marcos,Solà, Ricard,Fernández-Iba?ez, M. ángeles,Maciá, Beatriz
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p. 643 - 648
(2016/07/11)
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- Chiral Cyclopentadienone iron complexes for the catalytic asymmetric hydrogenation of ketones
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Three chiral (cyclopentadienone)iron complexes derived from (R)-BINOL (CK1-3) were synthesized and their structures unambiguously confirmed by X-ray analysis (CK3). Under suitable conditions for the in situ conversion into the corresponding (hydroxycyclopentadienyl)iron hydrides (Me3NO, H2), the new chiral complexes were tested in the catalytic asymmetric hydrogenation of ketones, showing moderate to good enantioselectivity. In particular, the complex bearing methoxy substituents at the 3,3-positions of the binaphthyl moiety (CK2) proved remarkably more enantioselective than the unsubstituted one (CK1) and reached the highest level of enantioselectivity (up to 77% ee) ever obtained with chiral (cyclopentadienone)iron complexes. Reducto! Chiral (cyclopentadienone)iron complexes were synthesized and tested, after in situ activation, in the catalytic asymmetric hydrogenation of ketones leading to the highest enantiomeric excesses ever obtained with this type of catalysts.
- Gajewski, Piotr,Renom-Carrasco, Marc,Facchini, Sofia Vailati,Pignataro, Luca,Lefort, Laurent,De Vries, Johannes G.,Ferraccioli, Raffaella,Forni, Alessandra,Piarulli, Umberto,Gennari, Cesare
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supporting information
p. 1887 - 1893
(2015/03/18)
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- Synthesis of several polyethers derived from BINOL and their application in the asymmetric borane reduction of prochiral ketones
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Several novel epoxy monomers, (S,S)- or (S,R)-3-(glycidyloxy)methyl-2,2′-bis(methoxymethyloxy)-1,1′-binaphthalene and (S,S)- or (S,R)-6-(glycidyloxy)methyl-2,2′-bis(methoxymethyloxy)-1,1′-binaphthalene, which were derived from chiral BINOL and epichlorohydrin, were synthesized and underwent anionic polymerization and deprotection of the MOM groups to obtain soluble polyethers. These polyethers were used to induce the enantioselective borane reduction of prochiral ketones. The substrates gave up to 98% yield with over 99% ee values. The recovered polyethers could be reused many times to induce the enantioselective reduction of prochiral ketones without losing their enantioselective induction ability.
- Zhang, An-Lin,Yu, Zeng-Da,Yang, Li-Wen,Yang, Nian-Fa
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p. 173 - 179
(2015/03/04)
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- Efficient asymmetric transfer hydrogenation of ketones in ethanol with chiral iridium complexes of spiroPAP ligands as catalysts
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Highly efficient iridium catalyzed asymmetric transfer hydrogenation of simple ketones with ethanol as a hydrogen donor has been developed. By using chiral spiro iridium catalysts (S)-1a a series of alkyl aryl ketones were hydrogenated to chiral alcohols with up to 98% ee.
- Liu, Wei-Peng,Yuan, Ming-Lei,Yang, Xiao-Hui,Li, Ke,Xie, Jian-Hua,Zhou, Qi-Lin
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supporting information
p. 6123 - 6125
(2015/04/14)
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- Synthesis of (R)-BINOL-Derived (Cyclopentadienone)iron Complexes and Their Application in the Catalytic Asymmetric Hydrogenation of Ketones
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A family of chiral (cyclopentadienone)iron complexes, featuring an (R)-BINOL-derived backbone, and their application in the asymmetric hydrogenation of ketones are described. The complexes differ from each other in the substituents at the 3,3′-positions of the binaphthyl residue (H, OH, OR, OCOR, OSO2R) or at the 2,5-positions of the cyclopentadienone ring [trimethylsilyl (TMS) or Ph]. Remarkably, eight precatalysts with different 3,3′-binaphthyl substitution [(R)-1c-1j] were synthesized from a common parent complex [(R)-1b] through direct functional group interconversion reactions of the complexes. The 3,3′-(bis)methoxy-substituted precatalyst (R)-1b gave the best catalytic performance, and its application scope was assessed in the hydrogenation of several ketones. The observed ee values (up to 77%) are much higher than those previously reported for other chiral (cyclopentadienone)iron complexes.
- Gajewski, Piotr,Renom-Carrasco, Marc,Facchini, Sofia Vailati,Pignataro, Luca,Lefort, Laurent,De Vries, Johannes G.,Ferraccioli, Raffaella,Piarulli, Umberto,Gennari, Cesare
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supporting information
p. 5526 - 5536
(2015/09/01)
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- Synthesis and characterization of novel chiral bidentate P,N-containing ligands and ruthenium(II) complex. the application in asymmetric transfer hydrogenation of ketones
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Novel chiral bidentate P,N-containing ligands have been easily synthesized by Schiff-base condensation of o-(diphenylphosphino)benzaldehyde and modified chiral diamine, (R,R)-2-(2,5-dimethyl-pyrrol-1-yl)-cyclohexylamine, further reduction with NaBH4. The chiral ruthenium(II) complex could be successfully prepared from the reaction between chiral bidentate aminophosphine ligand and RuCl2(PPh3)3. The chiral bidentate P,N-containing ligands and ruthenium(II) complex were fully characterized by NMR, IR, HRMS and single-crystal X-ray diffraction studies. In the presence of KOH, the asymmetric transfer hydrogenation (ATH) of various ketones catalyzed by the chiral ruthenium(II) complex proceeded smoothly under mild conditions, affording corresponding chiral secondary alcohols with up to 99% conversion and up to 60% ee. Additive such as NH4I was found to be helpful to promoting the enantioselectivity.
- Zeng, Li,Wu, Fang,Li, Yan-Yun,Dong, Zhen-Rong,Gao, Jing-Xing
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supporting information
p. 34 - 39
(2014/05/20)
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- Hydrogen: A good partner for rhodium-catalyzed hydrosilylation
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The influence of hydrogen pressure on the hydrosilylation of ketones catalyzed by [((S)-SYNPHOS)Rh(nbd)]OTf has been studied. We have notably demonstrated that hydrogen significantly affected the outcome of the reaction while not being consumed as stoichiometric reducing agent. In THF, diethyl ether or toluene, the hydrogen pressure exceedingly accelerated the hydrosilylation reaction and preserved or even improved the enantioselectivity of the process. In CH2Cl2, the rhodium catalyst also showed generally higher catalytic activity under hydrogen pressure. Most serendipitously, several ketones were found to give products of absolute opposite configuration upon performing the hydrosilylation under argon atmosphere or under hydrogen pressure. Copyright 2014 John Wiley & Sons, Ltd. We have shown that the performances of a rhodium complex associated with the atropisomeric diphosphine SYNPHOS as chiral ligand can be considerably upgraded under hydrogen pressure. Most serendipitously, several ketones were found to give the products of absolute opposite configuration upon performing the hydrosilylation under argon atmosphere or under H2 pressure. Copyright
- Balan, Cedric,Pop, Roxana,Comte, Virginie,Poinsot, Didier,Ratovelomanana-Vidal, Virginie,Gendre, Pierre Le
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p. 517 - 522
(2014/07/07)
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- Extending the range of pentasubstituted cyclopentadienyl compounds: The synthesis of a series of tetramethyl(alkyl or aryl)cyclopentadienes (Cp?R), their iridium complexes and their catalytic activity for asymmetric transfer hydrogen
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Tetramethyl(alky or aryl)cyclopentadienes were synthesized and the organometallic half-sandwich iridium complexes of the form [(η5-Cp?R)Ir(aa)Cl], Cp?R = tetramethyl(phenyl)cyclopentadienyl (Cp?
- Morris, David M.,McGeagh, Michael,De Pe?a, David,Merola, Joseph S.
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p. 120 - 135
(2015/02/19)
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- Synthesis and Lewis acid properties of a ferrocene-based planar-chiral borenium cation
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The first planar chiral ferrocenylborenium species (pR)-3+ is obtained in the enantiopure form by halide abstraction from the corresponding chloroborane adduct (pR)-2 using Krossing's salt. Competition experiments suggest that the Lewis acidity of (pR)-3+ is higher than that of B(C6F5)3 towards anions and slightly lower towards neutral Lewis bases. The ferrocenylborenium species (pR)-3+ is examined as a catalyst for the stereoselective hydrosilylation of ketones. The Royal Society of Chemistry.
- Chen, Jiawei,Lalancette, Roger A.,Jaekle, Frieder
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supporting information
p. 4893 - 4895
(2013/07/05)
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- TRANSITION METAL COMPLEXES OF AMINO ACIDS AND RELATED LIGANDS AND THEIR USE AS CATALYSTS, ANTI-MICROBIALS, AND ANTI-CANCER AGENTS
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The present invention relates to the fields of chemistry and pharmaceuticals. Embodiments of the present invention provide transition metal complexes of amino acids. Transition metal complexes of embodiments of the invention according to Categories I, II, III, and/or IV may be used as antimicrobial, anti-malarial, and anti-cancer agents, as well as catalysts in chemical reactions. Such compounds of the invention are particularly useful for combating multi-drug resistance against a broad range of microbials (such as MRSA and mycobacteria), including gram positive and gram negative bacteria, as well as can be used as anti-cancer agents against bladder cancer, breast cancer, colon cancer, rectal cancer, endometrial cancer, kidney cancer, leukemia, lung cancer, melanoma, non-Hodgkin's lymphoma, pancreatic cancer, prostate cancer, and thyroid cancer, to name a few.
- -
-
Paragraph 0247; 0248; 0252
(2013/04/24)
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- HYDROGENATION OF ESTERS OR CARBONYL GROUPS WITH TETRADENTATE AMINO/IMINO-THIOETHER BASED RUTHENIUM COMPLEXES
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The present invention relates to the field of catalytic hydrogenation and, more particularly, to the use of specific ruthenium catalysts, or pre-catalysts, in hydrogenation processes for the reduction of ketones and/or aldehydes into the corresponding alcohol respectively. Said catalysts are ruthenium complexes comprising a tetradentate ligand (L4) coordinating the ruthenium with: two nitrogen atoms, each in the form of a primary or secondary amine (i.e. a NH2 or NH group) or N-alkyl imine functional groups (i.e. a C═N group), and two sulfur atoms, each in the form of thioether functional groups.
- -
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Paragraph 0112
(2013/10/22)
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- Enantioselective oxidation of racemic secondary alcohols catalyzed by chiral Mn(iii)-salen complexes with N-bromosuccinimide as a powerful oxidant
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We demonstrate an efficient enantioselective oxidation of secondary alcohols catalyzed by Mn(iii)-salen complex using N-bromosuccinimide (NBS) as the oxidant. The new protocol is very efficient for the oxidative kinetic resolution of a variety of secondary alcohols, including ortho-substituted benzylic alcohols. The Royal Society of Chemistry 2012.
- Xu, Daqian,Wang, Shoufeng,Shen, Zhiqiang,Xia, Chungu,Sun, Wei
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supporting information
p. 2730 - 2732
(2012/11/07)
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- Ruthenium complexes of phosphino-substituted ferrocenyloxazolines in the asymmetric hydrogenation and transfer hydrogenation of ketones: A comparison
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Three novel routes have been developed for the synthesis of ferrocenyl-based phosphino-oxazolines in which the phosphino unit is attached to a ferrocenylmethyl or a ferrocenylethyl side chain. In two of the routes the phosphino-substituted ethyl side chain was built up diastereoselectively. Ruthenium complexes of the type [RuCl2PPh3(L)] of 12 bidentate phosphine-oxazoline ligands were synthesized, characterized, and tested in the transfer hydrogenation of acetophenone. For the best performing complexes a total of 12 additional ketones were screened in transfer hydrogenations and hydrogenations under transfer hydrogenation conditions. Two catalyst precursors in particular delivered products with an enantiomeric excess of up to 98% in transfer hydrogenations and 99% ee in hydrogenations. The transfer hydrogenation results obtained with all novel ligands were compared to those of two well-established FOXAP ligands. Furthermore, a qualitative comparison with the hydrogenation data was carried out. In both cases surprising similarities in product enantiomeric excess and product absolute configuration were found. Attempts were made to rationalize some of the observed features by considering a transition-state model. The molecular structures of one synthesis intermediate, two catalyst precursors, and two corresponding acetonitrile complexes were studied by X-ray diffraction.
- Zirakzadeh, Afrooz,Schuecker, Raffael,Gorgas, Nikolaus,Mereiter, Kurt,Spindler, Felix,Weissensteiner, Walter
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experimental part
p. 4241 - 4250
(2012/08/08)
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- Enantioselective borohydride reduction of aliphatic ketones catalyzed by ketoiminatocobalt(iii) complex with 1-chlorovinyl axial ligand
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For the enantioselective borohydride reduction of aliphatic ketones, the optically active ketoiminatocobalt(II) catalysts was successfully designed based on their axial ligand. Instead of chloroform for the aryl ketone reduction, various axial ligand precursors were examined for the aliphatic ketone. Consequently, 1, 1, 1-trichloroethane was found to be the most effective activator of the cobalt(II) complexes to generate the corresponding 1-chlorovinyl cobalt(III) derivatives as the reactive intermediate. Several aliphatic ketones were successfully reduced to afford the corresponding secondary alcohols with high enantioselectivities.
- Tsubo, Tatsuyuki,Chen, Hsiu-Hui,Yokomori, Minako,Fukui, Kosuke,Kikuchi, Satoshi,Yamada, Tohru
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supporting information; experimental part
p. 780 - 782
(2012/09/22)
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- Homogeneous asymmetric transfer hydrogenation of ketones using a ruthenium catalyst anchored on chitosan: Natural chirality at work
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A pivaloyl functionalized chitosan biopolymer was used as a polyligand for the [Ru(p-cymene)Cl2] moiety. The functionalized biopolymer containing a metal to saccharide ratio of 0.33 was used as a catalyst for the asymmetric transfer hydrogenation of ketones. The reactions gave yields up to 80% and enantiomeric excesses up to 72%, with the intrinsic chirality of chitosan being the only source of enantioselection.
- Babin, Mathieu,Clement, Roxanne,Gagnon, Jonathan,Fontaine, Frederic-Georges
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experimental part
p. 1548 - 1551
(2012/09/22)
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- Screening method for the evaluation of asymmetric catalysts for the reduction of aliphatic ketones
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ATH reductions of aliphatic ketones in water catalyzed by ruthenium coordinated by prolinamide ligands produce alcohols with moderate enantiomeric excesses in most cases. A set of seven aliphatic ketones is proposed for a rapid evaluation of the enantioselectivity of catalysts by one-pot multi-substrates reduction. The screening of a library of prolinamides shows that according to the structure of the ketones different ligands give the best asymmetric inductions.
- Boukachabia, Mourad,Zeror, Saoussen,Collin, Jacqueline,Fiaud, Jean-Claude,Zouioueche, Louisa Aribi
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supporting information; experimental part
p. 1485 - 1489
(2011/05/16)
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- Novel Ruthenium Complexes Having Hybrid Amine Ligands, Their Preparation And Use
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The invention relates to a novel class of ruthenium complexes containing phosphine and hybrid amine ligands, their preparation and use as catalysts in the reduction of simple ketones to alcohols by molecular hydrogenation. The reactivity and enantioselectivity of such complexes in the asymmetric hydrogenation of simple ketones could be enchanced by the addition of some selective additives.
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Page/Page column 10
(2011/05/03)
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- An unexpected directing effect in the asymmetric transfer hydrogenation of α,α-disubstituted ketones
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α,α-Disubstituted ketones containing an aromatic ring or alkene are reduced in high enantiomeric excess using an asymmetric transfer hydrogenation catalyst. The sense of reduction indicates that the unsaturated region of the ketone adopts a position adjacent to the Ru-bound η6-arene ring in the reduction transition state.
- Soni, Rina,Collinson, John-Michael,Clarkson, Guy C.,Wills, Martin
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supporting information; experimental part
p. 4304 - 4307
(2011/10/11)
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- Oxo-tethered ruthenium(II) complex as a bifunctional catalyst for asymmetric transfer hydrogenation and H2 hydrogenation
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Newly developed oxo-tethered Ru amido complexes (R,R)-1 and their HCl adducts (R,R)-2 exhibited excellent catalytic performance for both asymmetric transfer hydrogenation and the hydrogenation of ketonic substrates under neutral conditions without any cocatalysts to give chiral secondary alcohols with high levels of enantioselectivity.
- Touge, Taichiro,Hakamata, Tomohiko,Nara, Hideki,Kobayashi, Tohru,Sayo, Noboru,Saito, Takao,Kayaki, Yoshihito,Ikariya, Takao
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supporting information; experimental part
p. 14960 - 14963
(2011/11/05)
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- Copper-Catalyzed enantioselective hydrosilylation of ketones by using monodentate binaphthophosphepine ligands
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"Chemical Equation Presented" No base required: The first copper-catalyzed asymmetric hydrosilylation of carbonyl compounds by using monodentate binaphthophosphepine ligands is presented. After optimization of the reaction parameters, high yields and enantioselectivities (up to 96 % ee) for a broad range of aryl alkyl, cyclic, heterocyclic and aliphatic ketones are achieved without a base.
- Junge, Kathrin,Wendt, Bianca,Addis, Daniele,Zhou, Shaolin,Das, Shoubhik,Beller, Matthias
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experimental part
p. 68 - 73
(2010/03/03)
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- Chiral and nonchiral [OsX2(diphosphane)(diamine)] (X: Cl, OCH2CF3) complexes for fast hydrogenation of carbonyl compounds
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The osmium complexes trans-[OsCl2(dppf)(diamine)] (dppf: 1,1′-bis(diphenylphosphino)ferrocene; diamine: ethylenediamine in 3, propylenediamine in 4) were prepared by the reaction of [OsCl 2(PPh3)3] (1) with the ferrocenyl diphosphane, dppf and the corresponding diamine in dichloromethane. The reaction of derivative 3 with NaOCH2CF3 in toluene afforded the alkoxide cis-[Os(OCH2CF3)2(dppf) (ethylenediamine)] (5). The novel precursor [Os2Cl 4(P(m-tolyl)3)5] (2) allows the synthesis of the chiral complexes trans-[OsCl2(diphosphane)(1,2-diamine)] (6-9; diphosphane: (R)-[6,6′dimethoxy(1,1′-biphenyl)-2,2′-diyl] bis[1,1-bis(3,5-dimethylphenyl)phosphane] (xylMeObiphep) or (R)-(1,1′- binaphthalene)-2,2′-diylbis[1,1-bis(3,5-dimethylphenyl)phosphane] (xylbinap); diamine = (R,R)-1,2-diphenylethylenediamine (dpen) or (R,R)-l,2-diaminocyclohexane (dach)), obtained by the treatment of 2 with the diphosphane and the 1,2-diamine in toluene at reflux temperature. Compounds 3-5 in ethanol and in the presence of NaOEt catalyze the reduction of methyl aryl, dialkyl, and diaryl ketones and aldehydes with H2 at low pressure (5 atm), with substrate/catalyst (S/C) ratios of 10000-200000 and achieving turnover frequencies (TOFs) of up to 3.0x 105 h-1 at 70°C. By employment of the chiral compounds 6-9, different ketones, including alkyl aryl, bulky tertbutyl, and cyclic ketones, have successfully been hydrogenated with enantioselectivities up to 99% and with S/C ratios of 5000-100000 and TOFs of up to4.1xl04h-1at 60°C.
- Baratta, Walter,Barbato, Cinzia,Magnolia, Santo,Siega, Katia,Rigo, Pierluigi
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experimental part
p. 3201 - 3206
(2010/07/02)
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- Asymmetric hydrogenation of ketones catalyzed by a ruthenium(ii)-indan- ambox complex
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(S,R)-Indan-ambox ligand and its ruthenium(ii) complex have been prepared and successfully applied to asymmetric hydrogenation of prochiral simple ketones. A wide range of unfunctionalized ketones are reduced by Ru(ii)-indan-ambox catalyst with excellent enantioselectivities (up to 97% ee).
- Li, Wei,Hou, Guohua,Wang, Chunjiang,Jiang, Yutong,Zhang, Xumu
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supporting information; experimental part
p. 3979 - 3981
(2010/07/14)
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- The synthesis of chiral N-heterocyclic carbene-borane and -diorganoborane complexes and their use in the asymmetric reduction of ketones
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Chiral N-heterocyclic carbene-borane complexes have been synthesised, and have been shown to reduce ketones with Lewis acid promotion. Chiral N-heterocyclic carbene-borane and -diorganoborane complexes can reduce ketones with enantioselectivities up to 75
- Lindsay, David M.,McArthur, David
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supporting information; experimental part
p. 2474 - 2476
(2010/08/06)
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- Chiral iridium(I) bis(NHC) complexes as catalysts for asymmetric transfer hydrogenation
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The common use of NHC complexes in transition-metal mediated C-C coupling and metathesis reactions in recent decades has established W-heterocyclic carbenes as a new class of ligand for catalysis. The field of asymmetric catalysis with complexes bearing N
- Diez, Claus,Nagel, Ulrich
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experimental part
p. 509 - 516
(2010/10/18)
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- Enantioselective hydrosilylation of prochiral ketones catalyzed by chiral BINAP-copper(I) complexes
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The CuCl/NaOt-Bu/BINAP system was found to efficiently catalyze the hydrosilylation of aryl alkyl ketones with excellent enantioselectivities by using phenyl methyl silane as a stoichiometric hydride source. High enantiomeric excesses (up to 97%) and excellent yields (up to 99%) were obtained.
- Issenhuth, Jean-Thomas,Dagorne, Samuel,Bellemin-Laponnaz, Stéphane
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experimental part
p. 353 - 357
(2010/12/19)
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- Assignment of the absolute configurations of l-Aryl-2-propanols with the use of phosphoroselenoyl chlorides as chiral derivatizing agents
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Phosphoroselenoyl chloride bearing a l,1′-bi-2-naphthyl group was reacted with racemic 2-alkanols to give the corresponding esters. Based on the multiple combination of their NMR spectra, a method for the assignment of the absolute configuration of 1 -aryl-2-propanols was established. The solidstate conformations of the esters were confirmed by X-ray structure analyses.
- Murai, Toshiaki,Tsuji, Hiromi,Imaizumi, Satoko,Maruyama, Toshifumi
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supporting information; experimental part
p. 524 - 526
(2010/09/05)
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- Enantioselective reduction of aliphatic ketones using oxazaborolidine catalyst generated in situ from chiral lactam alcohol and phenoxyborane
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Oxazaborolidine catalyst generated in situ from chiral lactam alcohol 3 and p-iodophenoxyborane at room temperature was found to catalyze the enantioselective borane reduction of various prochiral aliphatic ketones at -20 °C with high enantioselectivity up to 98% ee. Copyright
- Kawanami, Yasuhiro,Mikami, Yudai,Hoshino, Katsuhiro,Suzue, Mikiko,Kajihara, Izumi
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supporting information; experimental part
p. 722 - 723
(2011/04/21)
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- NOVEL RUTHENIUM COMPLEXES HAVING HYBRID AMINE LIGANDS, THEIR PREPARATION AND USE
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The invention relates to a novel class of ruthenium complexes containing phosphine and hybrid amine ligands, their preparation and use as catalysts in the reduction of simple ketones to alcohols by molecular hydrogenation. The reactivity and enantioselectivity of such complexes in the asymmetric hydrogenation of simple ketones could be enchanced by the addition of some selective additives.
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Page/Page column 22; 23
(2010/01/07)
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- Iron(II) complexes for the efficient catalytic asymmetric transfer hydrogenation of ketones
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Iron(II) carbonyl compounds of the type trans-[Fe(NCMe)(CO)(P-N-N-P)] [BF4]2 bearing the ethylenediamine-derived diiminodiphosphine ligands (R,R)- or (5,5)-1,2-diphenyl-1,2-diaminoethane were synthesized and characterized, including by their crystal structures. The new complexes are suitable precatalysts for the transfer hydrogenation of ketones at room temperature, giving turnover frequencies of up to 2600 h-1 with low catalyst loadings (0.025-0.17%). Screening experiments showed that the precatalysts are able to produce alcohols from a wide range of simple ketones. For sterically demanding prochiral ketones, excellent enantioselectivities were obtained (up to 96% ee).
- Meyer, Nils,Lough, Alan J.,Morris, Robert H.
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scheme or table
p. 5605 - 5610
(2010/02/28)
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- Catalytic asymmetric borane reduction of prochiral ketones by using (S)-2-(anilinomethyl)pyrrolidine
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Catalytic asymmetric borane reduction of prochiral ketones was examined in the presence of (S)-2-(anilinornethyl)pyrrolidine. Chiral secondary alcohols were obtained with moderate to high enantiomeric excesses (up to 96% ee).
- Hosoda, Naoya,Iogawa, Yoshihiro,Shimada, Yuichi,Asami, Masatoshi
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experimental part
p. 274 - 277
(2009/03/12)
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- Solvent-induced chirality in the hydroboration of ketones
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The influence of the systematic variation of chiral solvents and of diverse Lewis acids on the asymmetric induction of the hydroboration of acetophenone has been studied. None of the solvents used could surpass lactic acid methyl ester, and for the Lewis acids, ZnCl2 and ZnI2 showed positive effects on the enantiomeric excess (ee) and the conversion. Also, the effect of the substrate structure was investigated by comparing the conversion and ee of eight different ketones. Apparently, the achievable asymmetric induction was higher with aromatic ketones. CSIRO 2008.
- Baldauf, Christoph,Dickerhof, Nina,Huettenhain, Stefan H.,Kern, Stefanie,Krummrich, Nancy,Kruse, Friedrich,May, Janine,Meister, Melanie,Mueller, Kristina,Rauer, Sabine,Salwig, Isabelle,Scharfenecker, Nico,Spitznagel, Birgit
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p. 414 - 418
(2008/12/20)
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- Chiral bis(pyridylimino)isoindoles: A highly modular class of pincer ligands for enantioselective catalysis
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(Chemical Equation Presented) Protect your back: Chiral wedges (red, see scheme) at the wingtips of bis(2-pyridylimino) isoindole (bpi) pincer ligands with an appropriate protective hedge (green), to block the metal center from backside attack, in the backbone represent a new class of efficient 3d-metal catalysts. These catalysts gave excellent enantioselectivities in the iron-catalyzed hydrosilylation of arylketones and in the cobalt-catalyzed cyclopropanation of alkenes.
- Langlotz, Bjoern K.,Wadepohl, Hubert,Gade, Lutz H.
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supporting information; body text
p. 4670 - 4674
(2009/02/06)
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- Further 'tethered' Ru(II) catalysts for asymmetric transfer hydrogenation (ATH) of ketones; the use of a benzylic linker and a cyclohexyldiamine ligand
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The synthesis and characterisation of two new Ru(II) catalysts for the asymmetric transfer hydrogenation (ATH) of ketones is described. In the case of 4, the novelty lies in the use of a benzyl tethering group between the asymmetric ligand part (TsDPEN) a
- Martins, Jose E.D.,Morris, David J.,Tripathi, Bhavana,Wills, Martin
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experimental part
p. 3527 - 3532
(2009/02/05)
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- Synthesis of three novel chiral diamines derived from (S)-proline and their evaluation as precursors of diazaborolidines for the catalytic borane-mediated enantioselective reduction of prochiral ketones
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A series of chiral diazaborolidine catalysts are readily prepared in situ at 75 °C in toluene solvent and under microwave irradiation (100 W, 15 min, air cooling) using chiral diamines derived from inexpensive and commercially available (S)-proline and borane-dimethyl sulfide. Special mention deserves the synthesis of potentially versatile diamine (S)-8 [(S)-(pyrrolidin-2-yl)diphenylmethanamine], with the key step being the conversion of tertiary alcohol (S)-(1-benzylpyrrolidin-2-yl)diphenyl methanol, (S)-12, to azide (S)-13. The chiral diazaborolidine/BH3 reagent system was successfully employed in the enantioselective reduction of prochiral ketones to give the corresponding secondary alcohols in excellent yield and with up to 96% enantiomeric purities.
- Luis Olivares-Romero,Juaristi, Eusebio
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experimental part
p. 9992 - 9998
(2009/04/11)
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- Mild and practical reductions of prochiral ketones to chiral alcohols using the chiral boronic ester TarB-H
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Chiral alcohols are prepared under mild conditions in high enantiomeric excesses using the tartaric acid derived chiral boronic ester TarB-H. The phenylboronic acid was quantitatively recovered and recycled using a simple extraction with sodium hydroxide and diethyl ether. Aromatic and aliphatic secondary alcohols were prepared in up to 99% ee. Georg Thieme Verlag Stuttgart.
- Eagon, Scott,Kim, Jinsoo,Singaram, Bakthan
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experimental part
p. 3874 - 3876
(2009/06/18)
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