- Asymmetric amplification in catalysis by trans-1,2-diaminocyclohexane bistriflamide
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(Figure Presented) A strong asymmetric amplification is observed in the addition of diethylzinc on aromatic aldehydes in the presence of the bistriflamide of trans-1,2-diaminocyclohexane 3a. The asymmetric amplification originates from the insolubility of
- Satyanarayana, Tummanapalli,Ferber, Benoit,Kagan, Henri B.
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- Asymmetric amplification by kinetic resolution using a racemic reagent: Example in amine acetylation
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The reaction of a racemic reagent on a mixture of enantiomers with small ee (ee = enantiomeric excess) has been studied for amine acylation. A substantial asymmetric amplification could be- realized, for example, from 67 to > 95.5 ee. The combination of asymmetric amplifications is subsequently discussed. Two sequential asymmetric amplifications, one using a racemic reagent and another using a positive nonlinear effect allowed us to start from 1.5 % ee and end with a large amount of a product of 97% ee.
- Satyanarayana, Tummanapalli,Kagan, Henri B.
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- Solvent-free direct aza-Friedel-Crafts reactions between 3,4-dihydroisoquinoline and 1- or 2-naphthols
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A self-catalytic aza-Friedel-Crafts method was employed to generate 1-naphtholyl tetrahydroisoquinoline products under neat conditions. In addition, a derivative was prepared in its enantiomerically pure form and has shown moderate activity for asymmetric catalysis in the asymmetric diethylzinc addition to aldehydes.
- MacLeod, Patricia D.,Li, Zhiping,Feng, Jianqing,Li, Chao-Jun
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- Enantioselective addition of diethylzinc to aldehydes using immobilized chiral BINOL-Ti complex on ordered mesoporous silicas
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A chiral (S)-BINOL ligand has been covalently grafted on ordered mesoporous silicas-MCM-41 and SBA-15 and the resulting inorganic-organic hybrid materials used as chiral auxiliaries in Ti-promoted enantioselective addition of diethyl zinc to aldehydes und
- Pathak, Kavita,Bhatt, Achyut P.,Abdi, Sayed H.R.,Kureshy, Rukhsana I.,Khan, Noor-ul H.,Ahmad, Irshad,Jasra, Raksh V.
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- Deciphering the mechanism behind efficient enantioselective ethylation with thiazolidine-based amino alcohols
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Taking advantage of the opposite chirality of two privileged starting materials, l-cysteine and d-penicillamine, a wide range of thiazolidine-based amino alcohols was synthesized. l-Cysteine derivatives were more efficient chiral inductors than the d-peni
- Cacho, Vanessa R. G.,Costa, Dora C. S.,Murtinho, Dina,Nunes, Sandra C. C.,Pais, Alberto A. C. C.,Silva Serra, M. Elisa,Tavares, Nélia C. T.
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- Tridentate nitrogen phosphine ligand containing arylamine NH as well as preparation method and application thereof
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The invention discloses a tridentate nitrogen phosphine ligand containing arylamine NH as well as a preparation method and application thereof, and belongs to the technical field of organic synthesis. The tridentate nitrogen phosphine ligand disclosed by the invention is the first case of tridentate nitrogen phosphine ligand containing not only a quinoline amine structure but also chiral ferrocene at present, a noble metal complex of the type of ligand shows good selectivity and extremely high catalytic activity in an asymmetric hydrogenation reaction, meanwhile, a cheap metal complex of the ligand can also show good selectivity and catalytic activity in the asymmetric hydrogenation reaction, and is very easy to modify in the aspects of electronic effect and space structure, so that the ligand has huge potential application value. A catalyst formed by the ligand and a transition metal complex can be used for catalyzing various reactions, can be used for synthesizing various drugs, and has important industrial application value.
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Paragraph 0095-0102; 0105-0109
(2021/06/26)
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- Linear β-amino alcohol catalyst anchored on functionalized magnetite nanoparticles for enantioselective addition of dialkylzinc to aromatic aldehydes
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A linear β-amino alcohol ligand, previously found to be a very efficient catalyst for enantioselective addition of dialkylzinc to aromatic aldehydes, has been anchored on differently functionalized superparamagnetic core-shell magnetite-silica nanoparticles (1a and 1b). Its catalytic activity in the addition of dialkylzinc to aldehydes has been evaluated, leading to promising results, especially in the case of 1b for which the recovery by simple magnetic decantation and reuse was successfully verified. This journal is
- Ciprioti, Stefano Vecchio,De Angelis, Martina,Di Pietro, Federica,Iannoni, Marika,Pilloni, Luciano,Primitivo, Ludovica,Ricelli, Alessandra,Righi, Francesco,Righi, Giuliana,Sappino, Carla,Suber, Lorenza
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p. 29688 - 29695
(2020/10/26)
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- Enantioselective Addition of Diethylzinc to Aromatic Aldehydes Using Novel Thiophene-Based Chiral Ligands
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Abstract: Chiral norephedrine-derived β-amino alcohols with a thiophene moiety were synthesized from thiophene carbaldehydes (methyl- or ethyl-substituted) and chiral amino alcohols, such as both enantiomers of norephedrine and 2-aminopropanol. The synthesized ligands were applied to the catalytic asymmetric addition of diethylzinc to aldehydes to obtain optically active alcohols with a high conversion (92%) and excellent enantioselectivities (ee up to 99%). The highest enantioselectivity (ee 99%) was obtained with p-trifluorobenzaldehyde as the substrate containing the strongly electron-acceptor CF3 group.
- Aydin, A. E.
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p. 901 - 909
(2020/07/03)
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- Enantioselective Addition of Diethylzinc to Aromatic Aldehydes Using Chiral Oxazoline-Based Ligands
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Abstract: Chiral oxazoline ligands containing an aromatic ring were prepared fromnorephedrine and pyrrole-2-carbonitrile or 2-hydroxybenzoyl chloride. Thesynthesized ligands were used in the copper-catalyzed asymmetric addition ofdiethylzinc to aromatic aldehydes to provide optically active 1-arylpropan-1-olswith high conversion (92%) and enantioselectivity (up to 99% ee).
- Aydin, A. E.
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p. 1304 - 1312
(2020/10/02)
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- Nickel-Catalyzed Enantioconvergent Borylation of Racemic Secondary Benzylic Electrophiles
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Nickel-catalyzed cross-coupling has emerged as the most versatile approach to date for achieving enantioconvergent carbon–carbon bond formation using racemic alkyl halides as electrophiles. In contrast, there have not yet been reports of the application of chiral nickel catalysts to the corresponding reactions with heteroatom nucleophiles to produce carbon–heteroatom bonds with good enantioselectivity. Herein, we establish that a chiral nickel/pybox catalyst can borylate racemic secondary benzylic chlorides to provide enantioenriched benzylic boronic esters, a highly useful family of compounds in organic synthesis. The method displays good functional group compatibility (e.g., being unimpeded by the presence of an indole, a ketone, a tertiary amine, or an unactivated alkyl bromide), and both of the catalyst components (NiCl2?glyme and the pybox ligand) are commercially available.
- Wang, Zhaobin,Bachman, Shoshana,Dudnik, Alexander S.,Fu, Gregory C.
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supporting information
p. 14529 - 14532
(2018/09/14)
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- New chiral amino alcohol ligands for catalytic enantioselective addition of diethylzincs to aldehydes
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A study aimed at the synthesis and structure optimization of new, efficient, optically active β-amino alcohol ligands with a structure suitable for immobilization on magnetite nanoparticles has been carried out. The optimized homogeneous amino alcohol catalysts 13a and 13b, the chirality of which arises from the Sharpless epoxidation of suitable allyl alcohols, were tested by employing the well-established enantioselective amino alcohol-promoted addition of diethylzinc to benzaldehyde, giving the corresponding benzyl alcohol with nearly quantitative yield and ee = 95%. Then, their broad applicability as chiral catalysts was evaluated by carrying out the same reaction on a family of aldehydes, including variously substituted aromatic ones as well as an aliphatic analogue. The results have confirmed the validity of the fine-tuning process performed on ligands 13a and 13b. In fact, both exhibited excellent catalytic activity as demonstrated by the chemical yields and ee obtained from all the tested aldehydes, almost independent of the position and type of substitution in the aromatic ring.
- Sappino, Carla,Mari, Alessandra,Mantineo, Agnese,Moliterno, Mauro,Palagri, Matteo,Tatangelo, Chiara,Suber, Lorenza,Bovicelli, Paolo,Ricelli, Alessandra,Righi, Giuliana
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p. 1860 - 1870
(2018/03/23)
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- Enantioselective alkylation of aromatic aldehydes with (+)-camphoric acid derived chiral 1,3-diamine ligands
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A series of chiral 1,3-diamine ligands derived from (+)-camphoric acid were prepared from the reaction of 1,3-diamino-1,2,2-trimethylcyclopentane with aromatic aldehydes, followed by reduction of the corresponding diimines. These newly synthesized ligands
- Serra, M. Elisa Silva,Murtinho, Dina,Paz, Victória
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p. 381 - 386
(2017/02/18)
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- Development of Axially Chiral Cyclo-Biaryldiol Ligands with Adjustable Dihedral Angles
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A new type of axially chiral cyclo-[1,1′-biphenyl]-2,2′-diol (CYCNOL) ligands with adjustable dihedral angles have been developed by varying the bridge chain length. Eight-, nine- and ten-membered cyclo-ligands were prepared and evaluated by using two representative examples: enantioselective additions of diethylzinc to aldehydes and organometallic reagents to enones. The results revealed that the fine regulation of dihedral angles through variation of the bridge chain length was effective in the asymmetric synthesis.
- Zhang, Pengxiang,Yu, Jipan,Peng, Fei,Wu, Xudong,Jie, Jiyang,Liu, Can,Tian, Hua,Yang, Haijun,Fu, Hua
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supporting information
p. 17477 - 17484
(2016/11/23)
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- Preparation of several BINOL-based polymeric ligands for the enantioselective addition of triethylaluminium to aromatic aldehydes
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The synthesis of several polystyrene-supported BINOL (1,1-binaphthol) ligands via radical polymerization is described. These BINOL-based polymeric ligands were applied to the enantioselective addition of triethylaluminium to aromatic aldehyde in the presence of titanium isopropoxide. The products were obtained with up to 93% enantiomeric excess (ee) in good to excellent yield. The ligands were easily recovered and reused without losing their catalytic activity as well as enantioselectivity.
- Liu, Dacai,Ouyang, Kunbing,Yang, Nianfa
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p. 1018 - 1023
(2016/01/30)
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- New chiral ligands derived from (+) and (-)-α-pinene for the enantioselective addition of diethylzinc to aldehydes
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In this study, we synthesized five new chiral ligands from (+) and (-)-α-pinene, which were successfully employed in the stereoselective addition of diethylzinc to aldehydes, leading to secondary chiral alcohols in up to 99% yield and 94% e.e.
- Frensch, Gustavo,Labes, Ricardo,Wosch, Celso Luiz,Munaretto, Laieli Dos Santos,Salomé, Kahlil Schwanka,Guerrero, Palimécio G.,Marques, Francisco A.
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supporting information
p. 420 - 422
(2016/01/12)
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- Enantioselective Addition of Diethylzinc to Aldehydes Catalyzed by Chiral O,N,O-tridentate Phenol Ligands Derived from Camphor
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Chiral O,N,O-tridentate phenol ligands bearing a camphor backbone were found to be effective chiral catalysts for the enantioselective addition of diethylzinc to aromatic aldehydes, resulting in high enantioselectivities (80-95% ee) at room temperature.
- Lee, Dong-Sheng,Chang, Shu-Ming,Ho, Chun-Ying,Lu, Ta-Jung
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- Enantioselective Ethylation of Various Aldehydes Catalyzed by Readily Accessible Chiral Diols
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Four chiral C2-symmetric diols were synthesized in a straightforward three-step reaction and demonstrated excellent enantioselectivities and good overall yields. Their catalytic activities were examined via the addition of diethylzinc to various aldehydes. The enantioselective addition of diethylzinc to 2-methoxybenzaldehyde gave the corresponding chiral secondary alcohol with high yields (up to 95%) and moderate to good enantiomeric excess (up to 88%). All synthesized ligands were evaluated in the addition of diethylzinc to various aldehydes in the presence of an additional metal such as Ti(IV) complexes. Chirality 28:593–598, 2016.
- G?k, Ya?ar,Kili?arslan, Seda,G?k, Halil Zeki,Karayi?it, ?lker ümit
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p. 593 - 598
(2016/08/27)
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- Synthesis of MeO-PEG2000-supported chiral ferrocenyl oxazoline carbinol ligand and its application in asymmetric catalysis
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A simple method for the synthesis of a MeO-PEG-supported chiral ferrocenyl oxazoline carbinol ligand has been developed. The chiral ligand was successfully applied to the catalytic asymmetric addition of diethylzinc to aryl aldehydes, affording secondary alcohols in high yields and with excellent enantioselectivities (up to 94% ee). The chiral ligand can be recovered and reused twice with no apparent loss of catalyst efficiency.
- Zhao, Wen-Xian,Liu, Guan-Jun,Wang, Jingjing,Li, Feng,Liu, Lantao
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p. 1133 - 1144
(2016/11/11)
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- Third-Generation Amino Acid Furanoside-Based Ligands from d-Mannose for the Asymmetric Transfer Hydrogenation of Ketones: Catalysts with an Exceptionally Wide Substrate Scope
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A modular ligand library of α-amino acid hydroxyamides and thioamides was prepared from 10 different N-tert-butyloxycarbonyl-protected α-amino acids and three different amino alcohols derived from 2,3-O-isopropylidene-α-d-mannofuranoside. The ligand library was evaluated in the half-sandwich ruthenium- and rhodium-catalyzed asymmetric transfer hydrogenation of a wide array of ketone substrates, including simple as well as sterically demanding aryl alkyl ketones, aryl fluoroalkyl ketones, heteroaromatic alkyl ketones, aliphatic, conjugated and propargylic ketones. Under the optimized reaction conditions, secondary alcohols were obtained in high yields and in enantioselectivities up to >99%. The choice of ligand/catalyst allowed for the generation of both enantiomers of the secondary alcohols, where the ruthenium-hydroxyamide and the rhodium-thioamide catalysts act complementarily towards each other. The catalytic systems were also evaluated in the tandem isomerization/asymmetric transfer hydrogenation of racemic allylic alcohols to yield enantiomerically enriched saturated secondary alcohols in up to 98% ee. Furthermore, the catalytic tandem α-alkylation/asymmetric transfer hydrogenation of acetophenones and 3-acetylpyridine with primary alcohols as alkylating and reducing agents was studied. Secondary alcohols containing an elongated alkyl chain were obtained in up to 92% ee. (Figure presented.).
- Margalef, Jèssica,Slagbrand, Tove,Tinnis, Fredrik,Adolfsson, Hans,Diéguez, Montserrat,Pàmies, Oscar
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p. 4006 - 4018
(2016/12/30)
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- Synthesis of dendrimer-supported ferrocenylmethyl aziridino alcohol ligands and their application in asymmetric catalysis
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A series of N-ferrocenylmethyl aziridino alcohol ligands bearing Frchet-type dendrimers were synthesized and applied in the asymmetric addition of diethylzinc to aldehydes affording chiral alcohols in excellent yields (up to 99%) and excellent enantiosele
- Zhao, Wen-Xian,Liu, Nian,Li, Gao-Wei,Chen, Dong-Li,Zhang, An-An,Wang, Min-Can,Liu, Lantao
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supporting information
p. 2924 - 2930
(2015/05/27)
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- Enantioselective addition of diethylzinc to aldehydes catalyzed by aziridine carbinols
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Abstract A series of enantiopure aziridine carbinols were synthesized from commercially available starting materials (l-serine and piperonylaldehyde), and characterized by 1H NMR, 13C NMR, HRMS, and IR. Their enantioselective induction behaviors were evaluated as chiral ligands in the asymmetric addition of diethylzinc and phenylethynylzinc to aryl and α,β-unsaturated aldehydes. Chiral aziridine carbinol 1h was found to catalyze the asymmetric addition of diethylzinc to aldehydes at low catalyst loadings (as little as 1 mol %), and the conversion rates were close to quantitative (up to 97% yield) with good to excellent enantiomeric excesses (up to 98% ee). A possible catalytic reaction mechanism is proposed.
- Wang, Xiaojuan,Zhao, Wenxian,Li, Gaowei,Liu, Guanjun,Wang, Jin,Wang, Mincan,Liu, Lantao
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p. 815 - 820
(2015/08/18)
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- Novel tridentate ligands derived from (+)-camphoric acid for enantioselective ethylation of aromatic aldehydes
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Novel tridentate ligands were prepared from (+)-camphoric acid, using simple synthetic sequences. The synthesized ligands were used in enantioselective ethylations of benzaldehydes, showing enantioselectivities up to 92%, at room temperature. Extending th
- Murtinho, Dina,Ogihara, Camila H.,Serra, M. Elisa Silva
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p. 1256 - 1260
(2015/11/16)
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- Stereoselective addition of diethylzinc to aldehydes using chiral β-hydroxy-2-oxazolines as catalysts
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Chiral β-hydroxy-2-oxazolines were synthesized and evaluated as catalysts for the addition of diethylzinc to aldehydes. All oxazolines proved effective in obtaining the addition products. The best enantiomeric excesses (69-78percent) were obtained using t
- Marques, Francisco A.,Wosch, Celso L.,Frensch, Gustavo,Labes, Ricardo,Maia, Beatriz H. L. N. S.,Salomé, Kahlil S.,Barisona, Andersson,Guerrero, Palimécio G.
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p. 165 - 170
(2015/02/19)
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- New atropisomeric amino alcohol ligands for enantioselective addition of diethylzinc to aldehydes
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Efficient synthesis of several new atropisomeric amino alcohols having 1-phenyl-1H-pyrrole skeleton are reported. Steric arrangements of the products were confirmed by a single-crystal X-ray measurement. The consequences of the size of the N-substituents
- Faigl,Deák,Erdélyi,Holczbauer,Czugler,Nyerges,Mátrav?lgyi
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p. 216 - 222
(2015/03/18)
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- Synthesis of quinazolinone-based aziridine diols as chiral ligands: Dual stereoselectivity in the asymmetric ethylation of aryl aldehydes Dedicated to Professor Dr. Metin Balci on the occasion of his retirement
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A new class of quinazoline-based enantiomerically pure aziridine diols 4a-d were prepared from the aziridination of mesityl oxide 3 with in situ generated 3-acetoxyaminoquinazolinone (S)-2b followed by NaBH4 reduction. Aziridine diols 4a-d were purified by means of column chromatography on silica gel and their stereochemistries were assigned by X-ray crystallography and NMR analysis. These aziridine diols 4 were evaluated as chiral ligands in the asymmetric addition of diethylzinc to aryl aldehydes, and ligand (S,R,R)-4a yielded (R)-1-phenylpropanol derivatives with up to 92% ee, while the diastereomer (S,S,R)-4c gave the opposite enantiomers (S)-1-phenylpropanol derivatives with up to 86% ee. The results demonstrate that switching the configuration of the aziridine alcohol moiety in ligand gives a remarkable reversal of enantioselectivity in the asymmetric addition of diethylzinc to aryl aldehydes.
- Celik, Saffet,Cakici, Murat,Kilic, Hamdullah,Sahin, Ertan
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p. 152 - 157
(2015/02/19)
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- Dual stereocontrolled alkylation of aldehydes with polystyrene-supported nickel complexes derived from α-amino amides
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Nickel(ii) complexes derived from α-amino amide ligands anchored to gel-type and monolithic polymers act as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes. Similar to the analogous homogeneous systems, dual stereocontrol in addition products can be achieved by controlling the stoichiometry of the immobilized nickel complex. Aromatic and aliphatic aldehydes were alkylated in good yields with enantioselectivities comparable to those obtained with the homogeneous analogues. These polymer-supported catalysts offer significant advantages as no metal leaching is observed and they can be easily recovered from the reaction mixture by simple filtration and reused for subsequent experiments with consistent catalytic activity.
- Escorihuela, Jorge,Altava, Beln,Burguete, M. Isabel,Luis, Santiago V.
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p. 14653 - 14662
(2015/02/19)
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- Facile synthesis and stereo-resolution of chiral 1,2,3-triazoles
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We describe herein the first facile synthesis of chiral triazoles through side chain functionalization. Readily available C-vinyl triazoles were used as starting materials, followed by sequential epoxidation, rearrangement and reduction to give the corresponding hydroxyl-triazoles. The CalB lipase catalyzed kinetic resolution gave enantiomerically pure (>99% ee) chiral triazoles in excellent yield. These new chiral TAs were also successfully applied as ligands in asymmetric addition of diethylzinc to aldehydes.
- Shi, Ye,Ye, Xiaohan,Gu, Qiang,Shi, Xiaodong,Song, Zhiguang
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supporting information
p. 5407 - 5411
(2015/05/20)
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- A new pyrrolidine-derived atropisomeric amino alcohol as a highly efficient chiral ligand for the asymmetric addition of diethylzinc to aldehydes
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A highly efficient pyrrolidine-derived atropisomeric amino alcohol, (Sa)-1-[2-diphenylhydroxymethyl-6-(trifluoromethyl)phenyl]-2-(1-pyrrolido)methyl-1H-pyrrole, has been synthesized as a chiral ligand for the enantioselective addition of diethylzinc to some prochiral aldehydes to afford (S)-alcohols. The conversion rates were close to quantitative with good to excellent enantiomeric excesses (up to 95% ee).
- Faigl, Ferenc,Erdélyi, Zsuzsa,Deák, Szilvia,Nyerges, Miklós,Mátrav?lgyi, Béla
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supporting information
p. 6891 - 6894
(2015/02/02)
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- The synthesis of chiral amino diol tridentate ligands and their enantioselective induction during the addition of diethylzinc to aldehydes
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A series of C2-symmetric chiral amino diol tridentate ligands 3a-g were prepared from achiral bulky organolithiums, achiral bulky primary amines, and optically active epichlorohydrin (ECH). The prepared C 2-symmetric chiral amino diol tridentate ligands were capable of inducing enantioselectivity in the model reaction of aromatic and aliphatic aldehydes with diethylzinc with an ee of up to 96%. The enantioselectivity can be modulated by adjusting the steric hindrance of the achiral reagents employed in the synthesis of the chiral ligand. The configuration of the addition product depended on the configuration of the amino diol ligands, which can be simply controlled as desired by using the ECH with the desired configuration during the preparation of the ligand.
- Zhang, An-Lin,Yang, Li-Wen,Yang, Nian-Fa,Liu, Yan-Ling
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p. 289 - 297
(2014/04/03)
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- Novel C2-symmetric chiral O,N,N,O-tetradentate 2,2-bipyridyldiolpropane ligands: Synthesis and application in asymmetric diethylzinc addition to aldehydes
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First synthesis of C2-symmetric chiral O,N,N,O-tetradentate 2,2-bipyridyldiolpropane ligands is described. The Mukaiyama-Michael reaction was applied as an important reaction for the synthesis of 2,2-bipyridylpropane 9. Among the ligands synthesized, ligand 11 exhibits excellent chiral induction (up to 97% ee) in diethylzinc addition to various aldehydes. The use of additional Lewis acid such as Ti(OiPr)4 in diethylzinc addition reaction is not required for the present catalytic system.
- Shih, Yi-Shan,Boobalan, Ramalingam,Chen, Chinpiao,Lee, Gene-Hsian
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p. 327 - 333
(2014/04/03)
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- Chiral porous TADDOL-embedded organic polymers for asymmetric diethylzinc addition to aldehydes
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Two chiral porous organic polymers (CPOPs) were synthesized by linking a TADDOL-embedded building block with arylethynylenes units. The CPOPs are highly stable to thermal treatment, moisture, acidity, and basicity. The dihydroxy groups of TADDOL inside th
- Wang, Xiuren,Zhang, Jie,Liu, Yan,Cui, Yong
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p. 435 - 440
(2014/04/17)
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- Enantioselective addition of diethylzinc to aromatic aldehydes catalyzed by C2-symmetric chiral diols
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Optically pure C2-symmetric diols have been synthesized with moderate yields in a straightforward manner, and are used as catalysts in the enantioselective alkylation of aromatic aldehydes with diethylzinc. The addition of diethylzinc to benzal
- G?k, Ya?ar,Keke?, Levent
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p. 2727 - 2729
(2014/05/06)
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- 3-Aminoquinazolinones as chiral ligands in catalytic enantioselective diethylzinc and phenylacetylene addition to aldehydes
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A series of readily known enantiomerically pure 3-aminoquinazolinones 1a-d were synthesised from easily accessible chiral pool α-hydroxy acids and α-amino acids in only four steps without any requirement of chromatography. These quinazolinones were examined as chiral ligands for catalytic enantioselective diethylzinc and phenylacetylene additions to aldehydes. For enantioselective alkylations, the effects of temperature, solvent, diethylzinc and ligand criteria were analysed, and the desired chiral alcohols were obtained in up to 86% ee. 3-Aminoquinazolinones 1a-d were also shown to be very useful ligands in enantioselective alkynylations of aldehydes. Based upon the optimised conditions, the corresponding propargylic alcohols were obtained in up to 94% ee.
- Karabuga, Semistan,Karakaya, Idris,Ulukanli, Sabri
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p. 851 - 855
(2014/06/23)
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- Straightforward access to chiral diol bidentate ligands: Their efficient enantioselective induction in the addition of diethylzinc to aromatic aldehydes
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Enantiopure C2-symmetric diol bidentate ligands have been synthesized in a straightforward manner through a three-step reaction with good yields. The synthesized C2-symmetric diol bidentate ligands were used in the addition of diethylzinc to various aromatic aldehydes, a general catalytic benchmark reaction, in order to assess their enantioselective induction properties. The enantioselective addition of diethylzinc to 1-naphthaldehyde and 3-chlorobenzaldehyde was achieved with an enantiomeric excess (ee) of up to 98%. All synthesized ligands were also evaluated in the addition of diethyzinc to aromatic aldehydes including an extra metal such as Ti(IV) (up to 99% ee).
- G?k, Yaar,Külolu, Soner,G?k, Halil Zeki,Kekec, Levent
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p. 835 - 838
(2015/02/19)
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- Straightforward access to chiral diol bidentate ligands: Their efficient enantioselective induction in the addition of diethylzinc to aromatic aldehydes
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Enantiopure C2-symmetric diol bidentate ligands have been synthesized in a straightforward manner through a three-step reaction with good yields. The synthesized C2-symmetric diol bidentate ligands were used in the addition of diethylzinc to various aromatic aldehydes, a general catalytic benchmark reaction, in order to assess their enantioselective induction properties. The enantioselective addition of diethylzinc to 1-naphthaldehyde and 3-chlorobenzaldehyde was achieved with an enantiomeric excess (ee) of up to 98%. All synthesized ligands were also evaluated in the addition of diethyzinc to aromatic aldehydes including an extra metal such as Ti(IV) (up to 99% ee).
- G?k, Ya?ar,Küloglu, Soner,G?k, Halil Zeki,Kekec?, Levent
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p. 835 - 838
(2015/04/16)
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- Ruthenium-catalyzed tandem-isomerization/asymmetric transfer hydrogenation of allylic alcohols
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A one-pot procedure for the direct conversion of racemic allylic alcohols to enantiomerically enriched saturated alcohols is presented. The tandem-isomerization/ asymmetric transfer hydrogenation process is efficiently catalyzed by [{Ru(p-cymene)Cl2}2] in combination with the a-amino acid hydroxyamide ligand 1, and performed under mild conditions in a mixture of ethanol and THF. The saturated alcohol products are isolated in good to excellent chemical yields and in enantiomeric excess up to 93%.
- Slagbrand, Tove,Lundberg, Helena,Adolfsson, Hans
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p. 16102 - 16106
(2015/01/09)
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- A catalytic and mechanistic investigation of optically active helical poly[3-(9-alkylfluoren-9-yl)propylene oxide]s in the enantioselective addition of ethylmagnesium bromide to aldehydes
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Optically active helical poly[(S)-3-(9-alkylfluoren-9-yl)propylene oxide]s (poly-(S)-AFPOs) without additional stereogenic units were used to induce the enantioselective addition of ethylmagnesium bromide to aldehydes, giving up to 53% ee of the products.
- Zhang, Anlin,Yang, Nianfa,Yang, Liwen,Peng, Dan
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supporting information
p. 462 - 464
(2014/04/17)
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- Modular prolinol chiral ligands for enantioselective addition of diethylzinc to aromatic aldehydes
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Enantioselective addition of diethylzinc (ZnEt2) to a series of aromatic aldehydes was promoted using a modular prolinol chiral ligand, 2-(S)-2-(hydroxydiphenylmethyl)pyrrolidin-1-yl)methyl)-4-nitrophenol (1a), without using titanium complex. The catalytic system employing 15 mol% of 1a was found to promote the addition of diethylzinc to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 86% ee of the corresponding secondary alcohol under mild conditions.
- Gou, Shaohua,Ye, Zhongbin,Feng, Mingming,Jiang, Wenchao
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p. 941 - 950
(2013/02/25)
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- Polystyrene-supported (2S)-(-)-3-exo-piperazinoisoborneol: An efficient catalyst for the batch and continuous flow production of enantiopure alcohols
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A polystyrene-supported analog (PS-PIB) of 3-exo-morpholinoisoborneol (MIB), designed for increased chemical stability, has been synthesized and used as a ligand in the asymmetric alkylation of aldehydes with Et2Zn. The supported ligand turned out to be highly active and enantioselective for a broad scope of substrates (92-99% ee), allowing repeated recycling. A single-pass, continuous flow process implemented with PS-PIB shows only a marginal decrease in conversion after 30 h of operation.
- Osorio-Planes, Laura,Rodriguez-Escrich, Carles,Pericas, Miquel A.
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supporting information; experimental part
p. 1816 - 1819
(2012/07/03)
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- Synthesis and application of novel dithiane alcohol ligand based on chiral cyclopropane-backbone for asymmetric ethylation of aromatic aldehydes
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A novel chiral dithiane alcohol ligand, based on chiral cyclopropane-backbone, was easily prepared from (-)- 1R-cis-caronaldehyde. The chiral ligand was used in asymmetric ethylation of aromatic aldehydes to afford the corresponding secondary alcohols wit
- Na, Risong,Wang, Bo,Liu, Honglei,Bian, Qinghua,Zhong, Jiangchun,Wang, Min,Guo, Hongchao
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p. 622 - 627
(2013/02/23)
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- Novel chiral thiazoline-containing NO ligands in the asymmetric addition of diethylzinc to aldehydes: Substituent effect on the enantioselectivity
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Several novel chiral thiazoline primary and tertiary alcohols were easily synthesized from commercially available l-cysteine in three steps and with high yield. These ligands were subsequently applied to the asymmetric addition of diethylzinc (Et2Zn) to various aldehydes. Products with S configuration were obtained when thiazoline-containing tertiary alcohol ligands were used as catalysts. The primary alcohol induced corresponding products with R configuration in 68% enantiomeric excess, which was a higher value relative to other NO ligands possessing a primary alcohol unit in the literature. Furthermore, a plausible transition state model was proposed to explain the observed enantioselectivities. Copyright
- Gong, Zhiyong,Liu, Qingwen,Xue, Pengchong,Li, Kechang,Song, Zhiguang,Liu, Zaiqun,Jin, Yinghua
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experimental part
p. 121 - 129
(2012/05/05)
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- Synthesis of chiral pyridylphenols for the enantioselective addition of diethylzinc to aldehydes
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Chiral 8-substituted 2-(8,10,10-trimethyl-6-aza-tricyclo[7.1.1.0 2,7]undeca-2(7),3,5-trien-5-yl)-phenols were prepared from a high enantiopurity (>97% ee) of (1R)-(+)-α-pinene, and assessed in the enantioselective addition of diethylzinc to substituted benzaldehydes, giving the (S)-alcohols with enantiomeric excess ranging from 33% to 89%. Interestingly, in all cases, except for those of ortho-chlorobenzaldehyde, ortho- and para-methoxybenzaldehydes, the ee was >71%. The plot of the Hammett substitution constants vs. enantiomeric excess of the diethylzinc addition to either the ortho- or para-substituted benzaldehydes shows a linear correlation.
- Wu, Pei-Shan,Chen, Chinpiao
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experimental part
p. 768 - 781
(2012/08/27)
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- Applications of conformational design: Rational resign of chiral ligands derived from a common chiral source for highly enantioselective preparations of (R)- and (S)-enantiomers of secondary alcohols
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A pair of diastereomers 7 and 8 were easily synthesized in only two steps from a single common chiral source according to the concept of conformation design. The efficiency of these chiral ligands was evaluated by their application to the asymmetric addition of diethylzinc to aldehydes. This catalytic asymmetric process afforded the a most efficient access to the (R)- and (S)-enantiomers of a given secondary alcohol with similarly outstanding enantioselectivities and high yields. Our results also showed that the control of the desired conformer's population by conformation design is a new and practical strategy for the rational and precise design of highly enantioselective chiral ligands for metal-catalyzed reactions. The mechanism and possible transition states for the catalytic asymmetric addition have been proposed on the basis of previous studies as well as the crystal structure of the chiral ligands 7 and 8.
- Wang, Min-Can,Wang, Yong-Hui,Li, Gao-Wei,Sun, Ping-Ping,Tian, Jie-Xi,Lu, Hui-Jie
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experimental part
p. 761 - 768
(2011/08/06)
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- Stereoselective synthesis of carane-based aminodiols as chiral ligands for the catalytic addition of diethylzinc to aldehydes
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Key intermediate epoxy alcohol 4 was prepared regio- and stereoselectively from (+)-3-carene 1 via carene oxide 2 and (-)-trans-allyl alcohol 3. The lithium perchlorate-catalysed ring opening of 4 with secondary and primary achiral and chiral amines resulted in primary, secondary and tertiary aminodiols. Aminodiols 5-14 were applied as chiral catalysts in the enantioselective addition of diethylzinc to benzaldehyde, resulting in (R)- and (S)-1-phenyl-1-propanol with moderate enantioselectivity. N-Benzyl, N-methyl, and (S)- and (R)-N-methylbenzyl derivatives 7 and 10-13 were transformed into 1,3-oxazines 17-21 via highly regioselective ring closures. When 17-21 were applied as chiral catalysts in the addition of diethylzinc to aromatic and aliphatic aldehydes, high chiral induction in the tricyclic catalysts was observed. The effects of the substituents on the nitrogen of the aminodiols and 1,3-oxazines were studied in detail; the best enantioselectivity was observed in the case of N-methylbenzyl-substituted oxazine 19.
- Szakonyi, Zsolt,Csillag, Kinga,Fueloep, Ferenc
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experimental part
p. 1021 - 1027
(2011/09/20)
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- Synthesis and asymmetric catalytic activity of (1S,1′S)-4,4′- biquinazoline-based primary amines
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A series of (1S,1′S)-4,4′-biquinazoline-based primary amines were prepared from natural amino acids via a six-step reaction sequence of protection and condensation followed by key synthetic steps including chlorination, nickel(0)-mediated homocoupling, and deprotection. These novel amines were screened for the asymmetric ethylation of aryl aldehydes to yield alcohols with an (S)-configuration with enantiomeric excesses (ee) varying from 2% to 95%.
- Cakici, Murat,Catir, Mustafa,Karabuga, Semistan,Ulukanli, Sabri,Kilic, Hamdullah
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experimental part
p. 300 - 308
(2011/05/17)
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- Sugar-monophosphite ligands applied to the asymmetric Ni-catalyzed trialkylaluminum addition to aldehydes
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A series of readily available sugar-based phosphite ligands were applied to the Ni-catalyzed asymmetric trialkylaluminum additions to aldehydes. The ability of the catalysts to transfer chiral information to the product could be tuned by choosing suitable ligand components (configuration at C-3 of the furanoside backbone; the steric hindrance of the substituent at C-3 and the substituents/configuration of the biaryl phosphite moieties). Good enantioselectivities (ee's up to 84%) were obtained for several aryl aldehydes using several organoaluminum sources.
- Alegre, Sabina,Dieguez, Montserrat,Pmies, Oscar
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experimental part
p. 834 - 839
(2011/08/22)
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- α-Pinene-type chiral Schiff bases as tridentate ligands in asymmetric addition reactions
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A group of tridentate Schiff bases derived from (+)-α-pinene were synthesized. The steric effects in the transition state, the importance of π-π stacking interactions as well as the electronic effects of aryl aldehydes according to Hammett constant values in the enantioselective addition of Et2Zn to aldehydes with the use of Schiff bases as chiral ligands are described. Also, a variety of aldehydes were cyanated using a catalyst prepared in situ from titanium tetraisopropoxide and chiral Schiff bases. The influence of a conjugated double-bond in the cyanation substrates on enantioselectivity was observed. The chemical structures of the chiral Schiff base-titanium alkoxide complexes are discussed based on their 1H and 13C NMR spectra. 3D models of the Zn2-complex catalyst and Ti-complex catalyst containing α-pinane-type Schiff bases based on X-ray diffraction experiments are postulated. The models presented were consistent with the reported chirality of the addition product and observed ee.
- Jaworska, Magdalena,Blocka, Ewelina,Kozakiewicz, Anna,Welniak, Miroslaw
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experimental part
p. 648 - 657
(2011/07/08)
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- Bidentate Schiff bases derived from (S)-α-methylbenzylamine as chiral ligands in the electronically controlled asymmetric addition of diethylzinc to aldehydes
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A group of bidentate Schiff bases derived from enantiomerically pure (S)-α-methylbenzylamine was synthesized. Crystal structure was determined for three compounds. Schiff bases were used as chiral ligands in the asymmetric addition of Et2Zn to aldehydes. The obtained enantioselectivity was e.e.=8-94% depending on the substrate and the best was observed for (S,E)-2-(1-(1-phenylethylimino)-ethyl)phenol. The enantioselectivity increase was connected with the substituent-induced electronic effects in the substrate molecules. Molecular modeling resulted in the models of the 3D structures of Zn-Zn complex catalysts containing investigated Schiff bases, which were consistent with the reported chirality of the addition product and explained observed e.e. The presented transition state models allow explaining the change of the absolute configuration of diethylzinc addition product in the case of using ortho-substituted aldehydes. ARKAT-USA, Inc.
- Jaworska, Magdalena,Welniak, Miroslaw,Zieciak, Justyna,Kozakiewicz, Anna,Wojtczakb, Andrzej
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experimental part
p. 189 - 204
(2011/08/21)
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- Synthesis of chiral sulfoximines derived from 3-aminoquinazolinones and their catalysis of enantioselective diethylzinc addition to aldehydes
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A series of sulfoxides were sulfoximinated using oxidative addition of 3-aminoquinazolinones by lead tetraacetate in the presence of hexamethyldisilazane. They were applied for the first time in catalytic enantioselective addition to aromatic aldehydes with a product enantiopurity (ee) of 92% in the case of 2-methoxybenzaldehyde.
- Karabuga, Semistan,Cakici, Murat,Kazaz, Cavit,Sahin, Ertan,Kilic, Hamdullah,Ulukanli, Sabri
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experimental part
p. 7887 - 7896
(2011/12/04)
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- Modular amino acid amide chiral ligands for enantioselective addition of diethylzinc to aromatic aldehydes
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Enantioselective addition of diethylzinc to a series of aromatic aldehydes was developed using a modular amino acid amide chiral ligand (2S)-3-phenyl-N-((R)-1-phenyl-ethyl)-2-(tosylamino)propanamide without using titanium complex. The catalytic system employing 10 mol% of 1g was found to promote the addition of diethylzinc (ZnEt2) to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 82% ee of the corresponding secondary alcohol under mild conditions.
- Gou, Shaohua,Ye, Zhongbin,Chang, Jing,Gou, Guangjun,Feng, Mingming
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experimental part
p. 448 - 453
(2012/02/03)
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- A systematic study of chiral homoprolinols and their derivatives in the catalysis of enantioselective addition of diethylzinc to aldehydes
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Homoprolinol analogs, a class of optically active γ-amino alcohols, were examined systematically in the enantioselective addition reactions of diethylzinc to aldehydes. By comparison of the results catalyzed by these γ-amino alcohols with those by the β-amino alcohols based on pyrrolidine architecture reported in the literature references, we have observed that the γ-amino alcohols are superior to the corresponding β-amino alcohols when the nitrogen and the oxygen are unsubstituted. Among the homoprolinols we tested, 2b gave the best results (45-88% yields, 44-81% ee) in the addition reactions. To the best of our knowledge, 2b has been noticed as one of the most efficient γ-amino alcohol catalysts based on pyrrolidine framework.
- Liu, Chang-Lu,Wei, Chang-Yong,Wang, Shi-Wen,Peng, Yun-Gui
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experimental part
p. 921 - 928
(2012/06/17)
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- Modular amino acids and β-amino alcohol-based chiral ligands for enantioselective addition of diethylzinc to aromatic aldehydes
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Enantioselective addition of diethylzinc to a series of aromatic aldehydes was developed using a modular amino acids and ${bf beta}$-amino alcohol-based chiral ligand (2R)-N-[(1R,2S)-1-hydroxy-1-phenylpropan-2-yl]-3- phenyl-2-(tosylamino) propanamide (1f) without using titanium complex. The catalytic system employing 15 mol% of 1f was found to promote the addition of diethylzinc (ZnEt2) to a wide range of aromatic aldehydes with electron-donating and electron-withdrawing substituents, giving up to 97% ee of the corresponding secondary alcohol under mild conditions.
- Gou, Shaohua,Ye, Zhongbin,Gou, Guangjun,Feng, Mingming,Chang, Jing
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experimental part
p. 110 - 116
(2012/06/18)
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- Structural and electronic effects of oxazolidine ligands derived from (1R,2S)-ephedrine in the asymmetric addition of diethylzinc to aldehydes
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The purpose of this research was to determine the activity of chiral oxazolidine ligands prepared from (1R,2S)-ephedrine for the enantioselective addition of diethylzinc to aldehydes. The configuration on the newly formed C2 stereogenic center was determined as (2S) by X-ray structural analysis. Oxazolidine ligands reveal medium enantioselectivity with the ee exceeding 57%, and the yields obtained being 68-99%. The results indicate that the absolute configuration of the addition product depends not only on the N3-methyl as an important stereocontrol element but also on both the electronic and steric effects of the substrates and oxazolidine ligands.
- Blocka, Ewelina,Jaworska, Magdalena,Kozakiewicz, Anna,Welniak, Miroslaw,Wojtczak, Andrzej
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experimental part
p. 571 - 577
(2010/08/06)
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- Enantioselective ethylation of aldehydes with 1,3-N-donor ligands derived from (+)-camphoric acid
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Derivatives of (+)-camphoric acid were prepared by a short and simple synthetic sequence and proved to be excellent ligands for the enantioselective ethylation of benzaldehyde with diethylzinc, with ees of up to 96% being obtained. The most efficient liga
- Murtinho, Dina,Elisa Silva Serra,Rocha Gonsalves, A.M.d'A.
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experimental part
p. 62 - 68
(2010/04/24)
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