- Design of a well-defined, silica-supported chiral Zn scaffold for enantioselective catalysis
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New compound Zn[(S,S)-iPr-pybox](Et)2 (1) was fully characterized, including by X-ray diffraction structural studies. Its grafting onto partially dehydroxylated silica affords material 2, which bears well-defined chiral (SiO)Zn[(S,S)-iPr-pybox]
- Ternel, Jeremy,Delevoye, Laurent,Agbossou-Niedercorn, Francine,Roisnel, Thierry,Gauvin, Regis M.,Thomas, Christophe M.
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- Chiral vanadyl Schiff base complex anchored on silicas as solid enantioselective catalysts for formation of cyanohydrins: Optimization of the asymmetric induction by support modification
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A series of vanadyl Schiff base complexes having a terminal carbon-carbon double bond pending alkyl chains of various lengths attached to the para position of the salen ligand were prepared and anchored on three large surface area silicas, i.e., amorphous
- Baleizao, Carlos,Gigante, Barbara,Garcia, Hermenegildo,Corma, Avelino
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- Lithium salts of chiral metallocomplex anions as catalysts for asymmetric trimethylsilylcyanation of aldehydes
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A series of the anionic CoIII complexes based on optically active amino acids containing the lithium cation in the external sphere of the complex was synthesized. The synthesized com- pounds were used as catalysts in the asymmetric addition of
- Maleev,Skrupskaya,Savel'eva,Mkrtchyan,Saghiyan
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- The asymmetric addition of trimethylsilylcyanide to aldehydes catalysed by anionic chiral nucleophiles. Part 2
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Studies have been carried out on the addition of trimethylsilylcyanide to aldehydes using highly active chiral lithium phenolate catalysts. The screening of a number of chiral phenolates has resulted in a system which gives the TMS ethers of cyanohydrins
- Holmes,Kagan
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- Catalytic, asymmetric cyanohydrin synthesis in propylene carbonate
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Propylene carbonate can be used as a green solvent for asymmetric cyanohydrin synthesis catalyzed by VO(salen)NCS. A range of 10 aromatic and aliphatic aldehydes gave high enantioselectivities (up to 93%) and conversions (up to 100%) in reactions carried
- North, Michael,Omedes-Pujol, Marta
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- Asymmetric trimethylsilylcyanation of benzaldehyde catalyzed by (salen)Ti(IV) complexes derived from (R)- and/or (S)-4-hydroxy-5-formyl[2.2]paracyclophane and diamines
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Benzaldehyde has been asymmetrically trimethylsilylcyanated, using chiral (salen)Ti(IV) catalysts 1a and 1b, 2a and 2b, 3a and 3b prepared in situ from titanium tetraisopropoxide and the Schiff's bases derived from (R)- or (S)-4-hydroxy-5-formyl[2.2]parac
- Belokon', Yuri,Moscalenko, Margarita,Ikonnikov, Nicolai,Yashkina, Lidia,Antonov, Dmitri,Vorontsov, Evgeni,Rozenberg, Valeria
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- Chiral ion pairs in catalysis: lithium salts of chiral metallocomplex anions as catalysts for asymmetric C-C bond formation
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A series of Co(III) anionic complexes of Schiff bases obtained from substituted salicylaldehydes and optically active amino acids has been synthesized. The ion pairing of these anions to a lithium cation can be used to induce asymmetry into lithium-cataly
- Belokon', Yuri N.,Maleev, Victor I.,Kataev, Dmitri A.,Saveleva, Tatiana F.,Skrupskaya, Tatiana V.,Nelyubina, Yulia V.,North, Michael
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- Asymmetric catalysis in a micro reactor - Ce, Yb and Lu catalysed enantioselective addition of trimethylsilyl cyanide to benzaldehyde
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A T-shaped micro reactor was used for the optimisation of reaction conditions for the enantioselective silylcyanation of benzaldehyde catalysed by lanthanide-pybox complexes. Compared to a conventional batch procedure, higher conversion was observed within shorter reaction time. The micro reactor process involving Lu(III) afforded essentially the same enantioselectivity as the batch process (73 vs 76% ee), whereas the enantioselectivity was lower in the micro reactor for catalysts containing Yb(III) (53 compared to 72%). Ce(III) provided very low selectivity in both types of processes (1 and 11% ee, respectively). A study of the effect of additives showed that the enantioselectivity in the Yb catalysed reaction performed in the micro reactor could be increased to 66%, whereas only a minor improvement, to 78% ee, was observed in the reaction with Lu. Graphical Abstract.
- J?nsson, Christina,Lundgren, Stina,Haswell, Stephen J.,Moberg, Christina
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- Encapsulation of Homogeneous Catalysts in Mesoporous Materials Using Diffusion-Limited Atomic Layer Deposition
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The heterogenization of homogeneous metal complex catalysts has attracted great attention. The encapsulation of metal complexes into nanochannels of mesoporous materials is achieved by coating metal oxides at/near the pore entrance by diffusion-limited atomic layer deposition (ALD) to produce a hollow plug. The pore size of the hollow plug is precisely controlled on the sub-nanometer scale by the number of ALD cycles to fit various metal complexes with different molecular sizes. Typically, Co or Ti complexes are successfully encapsulated into the nanochannels of SBA-15, SBA-16, and MCM-41. The encapsulated Co and Ti catalysts show excellent catalytic activity and reusability in the hydrolytic kinetic resolution of epoxides and asymmetric cyanosilylation of carbonyl compounds, respectively. This ALD-assisted encapsulation method can be extended to the encapsulation of other homogeneous catalysts into different mesoporous materials for various heterogeneous reactions.
- Zhang, Shufang,Zhang, Bin,Liang, Haojie,Liu, Yequn,Qiao, Yan,Qin, Yong
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- Asymmetric synthesis of cyanohydrins catalysed by a potassium Δ-bis[N-salicylidene-(R)-tryptophanato]cobaltate complex
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A chiral cobalt(III) complex of a Schiff base derived from (R)-tryptophan and salicylaldehyde catalysed asymmetric trimethylsilylcyanation of benzaldehyde at ambient temperature and a 20:1 substrate/catalyst ratio with the formation of enantiomerically en
- Belokon, Yuri N.,Bulychev, Alexander G.,Maleev, Victor I.,North, Michael,Malfanov, Ilja L.,Ikonnikov, Nikolai S.
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- Potassium and silver chiral cobaltate(III) complexes as precatalysts for asymmetric C-C bond formation
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Chiral, coordinatively-saturated cobaltate(III) complexes of Schiff bases obtained from salicylaldehyde and the optically active amino acids, (S)-Val, (S)-Thr, and (S)-Trp, are formed as C2-symmetrical, octahedral, anionic Λ(S,S)-, and Δ(S,S)-d
- Belokon, Yuri N.,Maleev, Viktor I.,Kataev, Dimitri A.,Mal'fanov, Ilya. L.,Bulychev, Alexander G.,Moskalenko, Margarita A.,Saveleva, Tat'yana F.,Skrupskaya, Tat'yana V.,Lyssenko, Konstantin A.,Godovikov, Ivan A.,North, Michael
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- Anionic chiral cobalt(III) complexes as catalysts of asymmetric synthesis of cyanohydrins
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Chiral coordinatively saturated cobalt(III) complexes with Schiff bases of enantio-pure amino acids are formed as Λ and Δ-isomers, which are not transformed into each other under normal conditions. These complexes catalyze the formation of enantiomerically enriched cyanohydrins from aldehydes and Me3SiCN under homo-and heterogeneous catalysis. Springer Science+Business Media, Inc. 2006.
- Belokon,Maleev,Mal'Fanov,Savel'Eva,Ikonnikov,Bulychev,Usanov,Kataev,North
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- Salen ligands revisited: synthesis and application of a planar chiral "Ferro-salen" ligand
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Condensation of the O-protected planar chiral hydroxyferrocene carbaldehyde (Sp)-1 with ethylenedlarcime, followed by deprotection gave rise to the "ferro-salen" ligand (Sp,Sp)-3 in good yield. This scaffold was used for t
- Niemeyer, Jochen,Kehr, Gerald,Froehlich, Roland,Erker, Gerhard
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- A study of substituent effects on the enantioselective trimethylsilylcyanation of benzaldehyde catalyzed by chiral Schiff base-titanium(IV) complexes
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New chiral Schiff base ligands derived from tert-butyl salicylaldehydes bearing electron withdrawing and donating groups were synthesized by reaction with various substituted chiral amino alcohols. These ligands were used with titanium tetraisopropoxide t
- Gama, Angeles,Flores-Lopez, Lucia Z.,Aguirre, Gerardo,Parra-Hake, Miguel,Somanathan, Ratnasamy,Cole, Thomas
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- Asymmetric trimethylsilylcyanation of aldehydes catalyzed by chiral salen TiIV complexes with the C1 symmetry
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Asymmetric trimethylsilylcyanation of a number of aromatic and aliphatic aldehydes catalyzed by chiral TiIV complexes prepared in situ from Ti(OPri)4 and (1S)-[N,N′-bis(2′-hydroxy-3′-tert-butylbenzylidene)]-1,2- diaminoalk
- Belokon',Yashkina,Moscalenko,Chesnokov,Kublitsky,Ikonnikov,Orlova,Tararov,North
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- Ultrasound-mediated synthesis of camphoric acid-based chiral salens for the enantioselective trimethylsilylcyanation of aldehydes
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New chiral salen ligands were prepared by the ultrasound-irradiated condensation of optically active (1R, 3S)-1,2,2-trimethyl-1,3- diaminocyclopentane with aromatic 1-hydroxyaldehydes. The ultrasound-mediated process is more convenient due to shorter reac
- Silva Serra, Maria E.,Murtinho, Dina,Goth, Albertino,D'A Rocha Gonsalves, Antonio M.,Abreu, Paulo E.,Pais, Alberto A. C. C.
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- Preparation of (S)-2-fluoronitriles
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(S)-2-fluoronitriles (S)-4 are obtained in good chemical and high optical yields from (R)-cyanohydrins (R)-2 or (R)-cyanohydrin trimethylsilylethers (R)-3 by fluorination with DAST or by nucleophilic substitution of α-sulfonyloxynitriles (R)-6, 7 with flu
- Stelzer,Effenberger
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- In situ formation of a heterobimetallic chiral [(salen)Ti IV]/[(salen)VV] catalyst for the asymmetric addition of TMSCN to benzaldehyde
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A mixed complex which results from two salen-derived VV and TiIV complexes (1 and 2), catalyzes the trimethylsilylcyanation of aldehydes. The reaction kinetics are largely determined by the titanium-derived portion, whereas the confi
- Belokon, Yuri N.,North, Michael,Maleev, Victor I.,Voskoboev, Nikolay V.,Moskalenko, Margarita A.,Peregudov, Alexander S.,Dmitriev, Andrey V.,Ikonnikov, Nikolai S.,Kagan, Henri B.
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- Preparation of diastereomerically pure and mixed (S)-PhGly/BIPHEP/Ru(II) complexes and their catalytic behavior with Li2CO3 in asymmetric cyanosilylation of benzaldehyde
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A diastereomerically mixed complex [Ru{(S)-phgly}2{(±)- biphep}] is readily prepared from achiral diphosphine BIPHEP in two steps. These diastereomers are then separated by silica gel column chromatography. A 61:39 equilibrium mixture of [Ru{(S
- Kurono, Nobuhito,Katayama, Taiki,Ohkuma, Takeshi
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- Asymmetric Baeyer-Villiger oxidation: Control of stereoelectronic demand
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The recent development of asymmetric Baeyer-Villiger oxidation of prochiral and racemic ketones is briefly summarized, focusing on the regio- and stereocontrol of the oxidation attained by regulating the stereoelectronic demand in the step of rearrangemen
- Katsuki
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- Chiral phenoxyimino-amido aluminum complexes for the asymmetric cyanation of aldehydes
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The reactivity of triethylaluminum towards salicylaldimine sulfonamides was probed, affording well-defined complexes through consecutive protonolysis of two Al-C bonds by the proligand. These complexes, when combined with an achiral anilinic N-oxide, catalyze the asymmetric addition of trimethylsilylcyanide to a wide range of aldehydes, with good activity and enantioselectivity (up to 91% ee). Insertion of the benzaldehyde substrate into the Al-N amido bond was observed, bringing elements for discussion around the nature of the actual active species.
- Ternel,Agbossou-Niedercorn,Gauvin
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Read Online
- Preparation method and application of a chiral Zr-MOF catalyst
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The invention relates to a preparation method and application of a chiral Zr-MOF catalyst and belongs to the technical field of chiral catalyst preparation. The structural formula of an organic ligandL of the chiral Zr-MOF catalyst is (R)-4,4'-dimethoxyca
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Paragraph 0071; 0072; 0075-0084
(2019/05/08)
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- Homochiral BINAPDA-Zr-MOF for Heterogeneous Asymmetric Cyanosilylation of Aldehydes
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A new homochiral BINAPDA-Zr-MOF was prepared by a new chiral organic linker of (R)-4,4′-(6,6′-dichloro-2,2′-diethoxyl-[1,1′-binaphthalene]-4,4′-diyl)dibenzoic acid (R-L) and ZrCl4 under solvothermal conditions. Its structure was determined by P
- Jin, Fa-Zheng,Zhao, Chen-Chen,Ma, Hui-Chao,Chen, Gong-Jun,Dong, Yu-Bin
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p. 9253 - 9259
(2019/07/08)
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- Chiral Metal-Organic Framework Decorated with TEMPO Radicals for Sequential Oxidation/Asymmetric Cyanation Catalysis
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A chiral porous metal-organic framework (MOF) decorated with radicals has been successfully constructed by cocrystallizing achiral (2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO)-substituted tricarboxylate and enantiopure VO(salen)-derived dipyridine ligands. The chiral MOF can function as an efficient heterogeneous catalyst for the sequential alcohol oxidation/asymmetric cyanation of aldehyde reactions with enhanced activity and enantioselectivity compared to the homogeneous counterpart.
- Li, Zijian,Liu, Yan,Kang, Xing,Cui, Yong
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supporting information
p. 9786 - 9789
(2018/08/28)
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- Multivariate Metal-Organic Frameworks as Multifunctional Heterogeneous Asymmetric Catalysts for Sequential Reactions
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The search for versatile heterogeneous catalysts with multiple active sites for broad asymmetric transformations has long been of great interest, but it remains a formidable synthetic challenge. Here we demonstrate that multivariate metal-organic frameworks (MTV-MOFs) can be used as an excellent platform to engineer heterogeneous catalysts featuring multiple and cooperative active sites. An isostructural series of 2-fold interpenetrated MTV-MOFs that contain up to three different chiral metallosalen catalysts was constructed and used as efficient and recyclable heterogeneous catalysts for a variety of asymmetric sequential alkene epoxidation/epoxide ring-opening reactions. Interpenetration of the frameworks brings metallosalen units adjacent to each other, allowing cooperative activation, which results in improved efficiency and enantioselectivity over the sum of the individual parts. The fact that manipulation of molecular catalysts in MTV-MOFs can control the activities and selectivities would facilitate the design of novel multifunctional materials for enantioselective processes.
- Xia, Qingchun,Li, Zijian,Tan, Chunxia,Liu, Yan,Gong, Wei,Cui, Yong
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supporting information
p. 8259 - 8266
(2017/06/28)
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- The first porphyrin-salen based chiral metal-organic framework for asymmetric cyanosilylation of aldehydes
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The first porphyrin-salen based chiral metal-organic framework (ps-CMOF) constructed by judiciously incorporating metalloporphyrin and metallosalen struts into one MOF structure is reported, which can serve as an effective heterogeneous catalyst for the a
- Li, Jiawei,Ren, Yanwei,Qi, Chaorong,Jiang, Huanfeng
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supporting information
p. 8223 - 8226
(2017/07/24)
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- A homochiral vanadium-salen based cadmium bpdc MOF with permanent porosity as an asymmetric catalyst in solvent-free cyanosilylation
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A homochiral vanadium-salen based MOF with the pcu topology is constructed via in situ synthesis under solvothermal conditions. The synthesized MOF exhibits BET surface areas of 574 m2 g-1, showing the highest H2 adsorptio
- Bhunia, Asamanjoy,Dey, Subarna,Moreno, José María,Diaz, Urbano,Concepcion, Patricia,Van Hecke, Kristof,Janiak, Christoph,Van Der Voort, Pascal
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supporting information
p. 1401 - 1404
(2016/01/25)
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- A hand natural acid radical ammonium salt crystal preparation and use
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The invention relates to a chiral amide salt crystal. The chemical formula of the chiral amide salt crystal is as shown in the specification. The (R)-3-methyl-butyl-1-hydroxymethylaminoformic acid-(R)-3-methyl-butyl-1-hydroxymethyl ammonium salt crystal s
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Paragraph 0039; 0040
(2017/01/26)
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- Chiral metal?Organic framework as a platform for cooperative catalysis in asymmetric cyanosilylation of aldehydes
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In this work, we demonstrate cooperative asymmetric catalysis by a metal?organic framework (MOF) as exemplified in the context of catalyzing cyanation of aldehydes with a VO(salen)-MOF, which after oxidation affords remarkably increased stereoselectivity (up to >99% ee) compared to the homogeneous VO(salen) counterpart as a result of the pairs of VO(salen) units in close proximity within its open channels. The cooperative asymmetric catalysis has been evidenced by the significantly decreased stereoselectivity and activity when one VO(salen) in such pairs of VO(salen) units is replaced with one Cu(salen), which results in blocking the VO?VO synergistic pathway while prompting unimolecular activation of substrates. The heterogeneous nature of VO(salen)-MOF has been verified by the fact that it can be easily recycled and reused without significant loss of catalytic activity and enantioselectivity, and its practical utility as asymmetric cyanation catalysist has been illustrated in the gram-scale synthesis of the antiviral natural products (R)- and (S)-enantiomers of tembamide. Our work therefore advances chiral MOF as an attractive platform for cooperative asymmetric catalysis in a variety of syntheses.
- Zhu, Chengfeng,Xia, Qingchun,Chen, Xu,Liu, Yan,Du, Xia,Cui, Yong
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p. 7590 - 7596
(2018/05/23)
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- Enantioselective cyanosilylation of aldehydes catalyzed by a multistereogenic salen-Mn(III) complex with a rotatable benzylic group as a helping hand
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A multistereogenic salen-Mn(iii) complex bearing an aromatic pocket and two benzylic groups as helping hands was found to be efficient in the catalysis of asymmetric cyanosilylation. The salen-Mn catalyst partially mimics the functions of biocatalysts by
- Wei, Yun-Long,Huang, Wei-Sheng,Cui, Yu-Ming,Yang, Ke-Fang,Xu, Zheng,Xu, Li-Wen
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p. 3098 - 3103
(2015/02/02)
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- Direct and Post-Synthesis Incorporation of Chiral Metallosalen Catalysts into Metal-Organic Frameworks for Asymmetric Organic Transformations
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Two chiral porous metal-organic frameworks (MOFs) were constructed from [VO(salen)]-derived dicarboxylate and dipyridine bridging ligands. After oxidation of VIV to VV, they were found to be highly effective, recyclable, and reusable
- Xi, Weiqin,Liu, Yan,Xia, Qingchun,Li, Zijian,Cui, Yong
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supporting information
p. 12581 - 12585
(2015/09/01)
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- A homochiral metal-organic framework as an effective asymmetric catalyst for cyanohydrin synthesis
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A homochiral metal-organic framework (MOF) of an enantiopure 2,2′-dihydroxy-1,1′-biphenyl ligand was constructed. After exchanging one proton of the dihydroxyl group for Li(I) ions, the framework is shown to be a highly efficient and recyclable heterogene
- Mo, Ke,Yang, Yuhua,Cui, Yong
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supporting information
p. 1746 - 1749
(2014/03/21)
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- Enantioselective cyanosilylation of aldehydes catalyzed by novel camphor derived Schiff bases-titanium(IV) complexes
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Five tridentate Schiff bases have been prepared from (1R,2S,3R,4S)-3-amino- 1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol and salicylaldehydes. X-ray structure investigation revealed differences in their molecular conformation, and their titanium(IV) complexes
- B?ocka, Ewelina,Bosiak, Mariusz J.,We?niak, Miros?aw,Ludwiczak, Agnieszka,Wojtczak, Andrzej
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p. 554 - 562
(2014/05/06)
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- Synthesis, characterization and catalytic property of chiral oxo-vanadium (+)-pseudoephedrine complex supported on magnetic nanoparticles Fe3O4 in the cyanosilylation of carbonyl compounds
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Vanadium complex of pseudoephedrine immobilized on magnetic nanoparticle Fe3O4[VO(Pseudoephedrine)@MNPs] was prepared and characterized by UV-vis, SEM, XRD, TGA, EDX, FT-IR, AGFM and elemental analysis techniques. VO(Pseudoephedrine)
- Rostami, Amin,Atashkar, Bahareh
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- 1-Aryl-2-((6-aryl)pyrimidin-4-yl)amino)ethanols as competitive inhibitors of fatty acid amide hydrolase
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A series of 1-aryl-2-(((6-aryl)pyrimidin-4-yl)amino)ethanols have been found to be competitive inhibitors of fatty acid amide hydrolase (FAAH). One member of this class, JNJ-40413269, was found to have excellent pharmacokinetic properties, demonstrated robust central target engagement, and was efficacious in a rat model of neuropathic pain.
- Keith, John M.,Hawryluk, Natalie,Apodaca, Richard L.,Chambers, Allison,Pierce, Joan M.,Seierstad, Mark,Palmer, James A.,Webb, Michael,Karbarz, Mark J.,Scott, Brian P.,Wilson, Sandy J.,Luo, Lin,Wennerholm, Michelle L.,Chang, Leon,Rizzolio, Michele,Chaplan, Sandra R.,Breitenbucher, J. Guy
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p. 1280 - 1284
(2014/03/21)
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- Dismantling the salen framework: Design of new asymmetric silylcyanation catalysts
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A series of novel chiral phenoxyimine Al(iii) complexes catalyzes asymmetric addition of SiMe3CN to a broad range of aldehydes with high yields and good to excellent enantioselectivities in the presence of a Lewis base.
- Ternel, Jeremy,Roussel, Pascal,Agbossou-Niedercorn, Francine,Gauvin, Regis M.
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p. 580 - 583
(2013/03/28)
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- The synthesis of tetradentate salens derived from (3R,4R)-N-substituted-3, 4-diaminopyrrolidines and their application in the enantioselective trimethylsilylcyanation of aromatic aldehydes
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The in situ formed Ti(IV) complexes of pyrrolidine-based chiral salen ligands derived from natural l-tartaric acid were evaluated as catalysts in the enantioselective trimethylsilylcyanation of aromatic aldehydes. The different activity and selectivity of the catalysts in the formation of the products were found to be dependent on the N-substituent of the pyrrolidine.
- Serra, M. Elisa Silva,Murtinho, Dina,Goth, Albertino
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p. 315 - 319
(2013/04/24)
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- Proline adducts of metallo-organic, sextuply-stranded lanterns as homogeneous catalysts for asymmetric catalysis
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Two homochiral metal-organic, sextuply-stranded, lantern-like complexes, Ce-L-Pro1 and Ce-D-Pro1, were synthesized via self-assembly by incorporating a L or D-pyrrolidine moiety within the respective ligands. The Ce-Pro1 complexes are comprised of chiral pyrrolidine-containing ligands and have lantern-like cavities. They function as asymmetric catalysts that promote cyanosilylation reactions with good conversions and enantioselectivity.
- Zhu, Wenting,Wu, Xiao,He, Cheng,Duan, Chunying
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p. 10477 - 10481
(2013/11/19)
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- New bifunctional organocatalysts based on (R,R)-cyclohexane-1,2-diamine for the asymmetric addition of nucleophiles to aldehydes
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The amide and sulfamide derivatives of (1R,2R)-N,N-diethylcyclohexane-1,2- diamine can serve as organocatalysts for addition of Me3SiCN and Et2Zn to aldehydes.
- Maleev,Gugkaeva,Tsaloev,Moskalenko,Khrustalev
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- A novel type of catalysts for the asymmetric C-C bond formation based on chiral stereochemically inert cationic Co iii complexes
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Schiff bases derived from (1R,2R)-1,2-diaminocyclohexane and 1 eq. of salycylic (or substituted salycylic) aldehyde form stereochemically inert positively charged chiral octahedral Co iii complexes of Δ-configuration with the stereoselectivity approaching 100%. To evaluate the calatylic activity and stereoinduction of the resulting complexes with various counteranions in the outer sphere, a model reaction of trimethylsilyl cyanide addition to benzaldehyde was used. O-trimethylsilylmandelonitrile formed in the process had an enantiomeric purity up to 27%. Complexes with F - counterion showed high catalytic activity.
- Belokon,Larionov,Mkrtchyan,Khrustalev,Nijland,Saghyan,Godovikov,Peregudov,Babievsky,Ikonnikov,Maleev
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p. 2252 - 2260
(2013/10/01)
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- Fine modification of salen ligands - Effects on the salen-Ti-catalyzed asymmetric cyanosilylation of aldehydes
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New bifunctional N-oxide salen-TiIV complexes and a pyrrolidine salen-TiIV complex in combination with achiral N-oxide were developed and applied to the asymmetric addition of trimethylsilyl cyanide to aldehydes. Notably, both enanti
- Lv, Chengwei,Cheng, Qigan,Xu, Daqian,Wang, Shoufeng,Xia, Chungu,Sun, Wei
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supporting information; experimental part
p. 3407 - 3411
(2011/09/12)
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- Cooperative thiourea-Bronsted acid organocatalysis: Enantioselective cyanosilylation of aldehydes with TMSCN
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We report a new thiourea - Bronsted acid cooperative catalytic system for the enantioselective cyanosilylation of aldehydes with yields up to 90% and enantioselectivities up to 88%. The addition of an achiral acid was found to be crucial for high asymmetric induction. Mechanistic investigations using a combination of NMR, ESI-MS, and density functional theory computations (including solvent corrections) at the M06/6-31G(d,p) level of theory suggest that the key catalytic species results from the cooperative interaction of bifunctional thioureas and an achiral acid that form well-defined chiral hydrogen-bonding environments.
- Zhang, Zhiguo,Lippert, Katharina M.,Hausmann, Heike,Kotke, Mike,Schreiner, Peter R.
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scheme or table
p. 9764 - 9776
(2012/01/03)
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- A practical Ti-salen catalyst based on dimeric salen ligand for asymmetric addition of trimethylsilyl cyanide to aldehydes
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A dimeric salen ligand derived from L-tartaric acid was synthesized through linking two salen units with 1,6-dibromohexane. The corresponding Ti complex was proved to be an efficient catalyst for asymmetric addition of trimethylsilyl cyanide to aldehydes,
- Lv, Chengwei,Xu, Daqian,Wang, Shoufeng,Miao, Cheng-Xia,Xia, Chungu,Sun, Wei
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experimental part
p. 1242 - 1245
(2012/01/06)
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- A novel bifunctional Ti(IV) complex catalyzed asymmetric silylcyanation of aldehydes
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A novel Lewis acid and Lewis base bifunctional Ti(IV) complex was formed in situ upon the treatment of ligand (R)-3,3′-bis(diphenylphosphinoyl)-BINOL with Ti(PrO-i)4, which is proven to be an efficient catalyst in the asymmetric trimethylsilylc
- Tang, Hongying,Zhang, Zhongbiao
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experimental part
p. 31 - 35
(2011/10/09)
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- CYANATION CATALYST AND METHOD FOR PRODUCING OPTICALLY ACTIVE CYANHYDRIN COMPOUND USING THE SAME
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The present invention can provide a cyanation catalyst represented by the general formula (I): (in the formula (I), R1 through R4 are each an optionally substituted hydrocarbon group; R1 and R2 and/or R3 and R4 may form an optionally substituted carbon chain ring; R5 through R8 are each a hydrogen atom, or an optionally substituted hydrocarbon group; R5 and R6 and/or R7 and R8 may form an optionally substituted carbon chain ring; R9 and R10 are each a hydrogen atom, or an optionally substituted hydrocarbon group; W, X and Y each represent an optionally substituted binding chain; X and/or Y may be non-existent; M represents a metal or a metal ion; and ligands of M may each be located at any position).
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Page/Page column 7
(2010/03/02)
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- Mechanistic comparison of aluminium based catalysts for asymmetric cyanohydrin synthesis
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A kinetic analysis of the asymmetric addition of trimethylsilyl cyanide to benzaldehyde using three aluminium based catalysts has been carried out. All three catalysts displayed rate equations, which were first order in trimethylsilyl cyanide concentratio
- North, Michael,Villuendas, Pedro,Williamson, Courtney
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experimental part
p. 1915 - 1924
(2010/04/24)
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- Salen-ligands based on a planar-chiral hydroxyferrocene moiety: Synthesis, coordination chemistry and use in asymmetric silylcyanation
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Condensation of the O-protected hydroxyferrocene carbaldehyde (Sp)-1 with suitable diamines, followed by liberation of the hydroxyferrocene moiety leads to a new type of ferrocene-based salen ligands (3). While the use of ethylenediamine in the
- Niemeyer, Jochen,Cloppenburg, Jeannine,Fr?hlich, Roland,Kehr, Gerald,Erker, Gerhard
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supporting information; experimental part
p. 1801 - 1812
(2010/08/05)
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- Enantioselective trimethylsilylcyanation of benzaldehyde using pyrrolidine-based chiral salen ligands
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The in situ formed Ti(IV) complexes of several pyrrolidine-based chiral salen ligands derived from natural (L)-tartaric acid were evaluated as catalysts in the enantioselective trimethylsilylcyanation of benzaldehyde. The catalysts were found to be very active, producing the corresponding product, O-trimethylsilylmandelonitrile, in high yields (>94%) and enantioselectivities of up to 88%.
- Serra, M. Elisa Silva,Murtinho, Dina,Goth, Albertino
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experimental part
p. 64 - 69
(2010/08/07)
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- Investigation of lewis acid versus lewis base catalysis in asymmetric cyanohydrin synthesis
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The asymmetric addition of trimethylsilyl cyanide to aldehydes can be catalysed by Lewis acids and/or Lewis bases, which activate the aldehyde and trimethylsilyl cyanide, respectively. It is not always apparent from the structure of the catalyst whether Lewis acid or Lewis base catalysis predominates. To investigate this in the context of using salen complexes of titanium, vanadium and aluminium as catalysts, a Hammett analysis of asymmetric cyanohydrin synthesis was undertaken. When Lewis acid catalysis is dominant, a significantly positive reaction constant is observed, whereas reactions dominated by Lewis base catalysis give much smaller reaction constants. [{Ti(salen)O}2] was found to show the highest degree of Lewis acid catalysis, whereas two [VO(salen)X] (X = EtOSO3 or NCS) complexes both displayed lower degrees of Lewis acid catalysis. In the case of reactions catalysed by [{Al(salen)}2O] and triphenyl- phosphine oxide, a non-linear Ham- mett plot was observed, which is indicative of a change in mechanism with increasing Lewis base catalysis as the carbonyl compound becomes more electron-deficient. These results suggested that the aluminium complex/tri- phenylphosphine oxide catalyst system should also catalyse the asymmetric addition of trimethylsilyl cyanide to ke- tones and this was found to be the case.
- North, Michael,Omedes-Pujol, Marta,Williamson, Courtney
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experimental part
p. 11367 - 11375
(2010/11/17)
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- The synthesis of novel tetradentate ligands derived from salen and their application in enantioselective silylcyanation of aldehydes
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Two new tetradentate ligands derived from salen have been prepared and their titanium complexes are used as chiral catalysts in the enantioselective silylcyanation of aldehydes, which give the silyl ethers of cyanohydrins in moderate to good enantiomeric
- Lv, Chengwei,Wu, Mei,Wang, Shoufeng,Xia, Chungu,Sun, Wei
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experimental part
p. 1869 - 1873
(2010/11/19)
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- Kinetics and mechanism of vanadium catalysed asymmetric cyanohydrin synthesis in propylene carbonate
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Propylene carbonate can be used as a green solvent for the asymmetric synthesis of cyanohydrin trimethylsilyl ethers from aldehydes and trimethylsilyl cyanide catalysed by VO(salen)NCS, though reactions are slower in this solvent than the corresponding re
- North, Michael,Omedes-Pujol, Marta
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experimental part
p. 1043 - 1055
(2011/03/22)
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- Straightforward enzymatic process based on HNL CLEA-catalysis towards cyanohydrin derivatives
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An efficient enzymatic process based on HNL-CLEA catalysis in buffer-saturated organic media was developed to limit the amount of overall waste generated and the number of safety issues incurred by handling HCN-containing waste. Starting from benzaldehyde as a model substrate, (R)- and (S)-mandelonitrile can be obtained under these reaction conditions without an extraction step being required. The crude cyanohydrin intermediate was sufficiently pure to be used as starting material in a second step towards a range of derivatives.
- Cabirol, Fabien L.,Lim, Angela E. C.,Hanefeld, Ulf,Sheldon, Roger A.
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experimental part
p. 114 - 118
(2010/04/28)
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- A bimetallic aluminium(salen) complex for asymmetric cyanohydrin synthesis
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In the presence of a phosphine oxide cocatalyst, a bimetallic aluminium(salen) complex was found to catalyse the asymmetric addition of trimethylsilyl cyanide to aldehydes. Under optimised conditions, enantioselectivities of 53-96% were obtained using 2 m
- North, Michael,Williamson, Courtney
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experimental part
p. 3249 - 3252
(2009/08/17)
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- The enantioselective cyanosilylation of aldehydes on a chiral VO(Salen) complex encapsulated in SBA-16
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A solid catalyst for enantioselective cyanosilylation of aldehydes was prepared by encapsulating a chiral vanadyl Salen complex [VO(Salen)] in the nanocage of SBA-16. After encapsulation, the pore entrance size of SBA-16 was finely tuned through a silylat
- Yang, Hengquan,Zhang, Lei,Wang, Peng,Yang, Qihua,Li, Can
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experimental part
p. 257 - 264
(2010/04/22)
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- Asymmetric cyanation of aldehydes, ketones, aldimines, and ketimines catalyzed by a versatile catalyst generated from cinchona alkaloid, achiral substituted 2,2′-biphenol and tetraisopropyl titanate
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Full investigation of cyanation of aldehydes, ketones, aldimines and ketimines with trimethylsilyl cyanide (TMSCN) or ethyl cyanoformate (CNCOOEt) as the cyanide source has been accomplished by employing an in situ generated catalyst from cinchona alkaloid, tetraisopropyl titanate [Ti(OiPr)4] and an achiral modified biphenol. With TMSCN as the cyanide source, good to excellent results have been achieved for the Strecker reaction of N-Ts (Ts=p-toluenesulfonyl) aldimines and ketimines (up to >99% yield and >99% ee) as well as for the cyanation of ketones (up to 99% yield and 98% ee). By using CNCOOEt as the alternative cyanide source, cyanation of aldehyde was accomplished and various enantioenriched cyanohydrin carbonates were prepared in up to 99% yield and 96% ee. Noteworthy, CNCOOEt was successfully employed for the first time in the asymmetric Strecker reaction of aldimines and ketimines, affording various a-amino nitriles with excellent yields and ee values (up to >99% yield and >99% ee). The merits of current protocol involved facile availability of ligand components, operational simplicity and mild reaction conditions, which made it convenient to prepare synthetically important chiral cyanohydrins and examino nitriles. Furthermore, control ex-periments and NMR analyses were performed to shed light on the catalyst structure. It is indicated that all the hydroxyl groups in cinchona alkaloid and biphenol complex with TiIV, forming the catalyst with the structure of (biphenoxide) Ti(OR*)(Oi'Pr). The absolute configuration adopted by biphenol 4 m in the catalyst was identified as S configuration according to the evidence from control experiments and NMR analyses. Moreover, the roles of the protonic additive ((iPrOH) and the tertiary amine in the cinchona alkaloid were studied in detail, and the real cyanide reagent in the catalytic cycle was found to be hydrogen cyanide (HCN). Finally, two plausible catalytic cycles were proposed to elucidate the reaction mechanisms.
- Wang, Jun,Wang, Wentao,Li, Wei,Hu, Xiaolei,Shen, Ke,Tan, Cheng,Liu, Xiaohua,Feng, Xiaoming
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supporting information; scheme or table
p. 11642 - 11659
(2010/04/28)
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- Enantioselective silylcyanation of aldehydes and ketones by a titanium catalyst prepared from a partially hydrolyzed titanium alkoxide and a Schiff base ligand
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In the presence of small amount (0.2-1.0 mol%) of a titanium complex catalyst prepared from a partially hydrolyzed titanium alkoxide and an optically active tridentate Schiff base ligand, the enantioselective silylcyanation of aldehydes and ketones procee
- Yoshinaga, Kazuhiko,Nagata, Takushi
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supporting information; experimental part
p. 1495 - 1498
(2011/02/24)
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- Exploring structural diversity in ligand design: The aminoindanol case
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A series of enantiopure ligands based on the aminoindanol scaffold, but differing in regio-and stereochemistry has been synthesized. These ligands have been conveniently derivatized and their catalytic efficiency in different enantioselective reactions has been screened to determine privileged candidates with respect to regio- and stereochemistry for each considered process. The nature of the amino substituent has been optimized for specific applications and this has led to the development of an efficient method for the preparation of bulky bicyclic amines by reductive amination.
- Rodriguez-Escrich, Sergi,Sola, Lluis,Jimeno, Ciril,Rodriguez-Escrich, Carles,Pericas, Miquel A.
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supporting information; experimental part
p. 2250 - 2260
(2009/10/06)
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- A new strategy for designing non-C2-symmetric monometallic bifunctional catalysts and their application in enantioselective cyanation of aldehydes
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A monometallic bifunctional catalyst, in which only one imidazolyl moiety is directly attached at the 3-position of a binaphthol moiety, has been developed. The ligand (R)-1, which lacks C2-symmetry and flexible linkers, in combination with Ti(OiPr)4, has been demonstrated to promote the enantioselective cyanation of aldehydes with trimethylsilylcyanide (TMSCN), giving excellent enantioselectivities of up to 98 % ee and high yields of up to 99%. The use of this bifunctional catalytic system obviates the need for additives and is extremely simple as the reagents are added in one portion at the beginning of the reaction. The protocol has been found to tolerate a relatively wide range of aldehydes when 10 mol% of the (R)-1/Ti(OiPr) 4 complex is deployed in CH2Cl2 at -40°C, the conditions which proved most practical and effective. The asymmetric cyanations also proceeded with lower catalyst loadings (5 mol%, or even 2 mol%), still giving satisfactory enantiomeric excesses and yields. Interestingly, the use of freshly distilled TMSCN dried over CaH2 gave a low enantioselectivity and only a moderate yield of the adduct as compared with direct use of the commercial reagent. The results of 13C NMR spectroscopic studies implicate HCN as the actual reactive nucleophile.
- Yang, Fei,Wei, Siping,Chen, Chien-An,Xi, Peihua,Yang, Li,Lan, Jingbo,Gau, Han-Mou,You, Jingsong
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scheme or table
p. 2223 - 2231
(2009/04/06)
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- Synthesis of chiral pyridyl alcohols using a two-step catalytic approach
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Chira l pyridyl alcohols have been prepared by developing a two-step approach that uses the asymmetric cyanation of aldehydes to give cyanohydrins and subsequent [2+2+2]-cyclotrimerization reaction with acetylene. Georg Thieme Verlag Stuttgart.
- Heller, Barbara,Redkin, Dmitry,Gutnov, Andrey,Fischer, Christine,Bonrath, Werner,Karge, Reinhard,Hapke, Marko
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- Titanium(IV)(salen) and yanadium(V)(salen) complexes derived from C 2- and C1-symmetric diamines for asymmetric cyanohydrin synthesis
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Titanium and vanadium salen complexes have been prepared from C 2- and C1-symmetric acyclic diamines. All of the complexes catalysed the asymmetric addition of trimethylsilyl cyanide to benzaldehyde and the sense of asymmetric induction was determined by the nature of the substituents. The vanadium complex of a valine-derived diamine gave good results with a range of aromatic and aliphatic aldehydes. Georg Thieme Verlag Stuttgart.
- Belokon', Yuri N.,Hunt, Jamie,North, Michael
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experimental part
p. 2150 - 2154
(2009/05/07)
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- Asymmetric catalysis of carbon-carbon bond forming reactions using amino acid-derived C1-symmetrical salen ligands
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Four amino acids (alanine, valine, phenylalanine and phenylglycine) have been converted into C1-symmetrical salen ligands and complexed to titanium, vanadium, copper and cobalt. The resulting complexes have been used as asymmetric catalysts for asymmetric cyanohydrin synthesis, asymmetric Strecker reactions, asymmetric synthesis of α-methyl amino acids and asymmetric Darzens condensations. Satisfactory levels of asymmetric induction were obtained from reactions in which the (salen)metal complex acts as a chiral Lewis acid, but low levels of asymmetric induction were obtained from reactions carried out under solid-liquid phase-transfer conditions.
- Belokon, Yuri N.,Hunt, Jamie,North, Michael
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experimental part
p. 2804 - 2815
(2009/06/28)
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