- 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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- Isosterically designed chiral catalysts: Rationale, optimization and their application in enantioselective nucleophilic addition to aldehydes
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Proline-based N,N′-dioxide ligands were designed on the basis of isosteric approach, and were successfully applied in enantioselective nucleophilic addition to aldehydes. In the presence of 10 mol% of chiral ligand 1b, enantioselective addition of diethylzinc to aldehydes provided the corresponding secondary alcohols in up to 90% isolated yield and up to 99% ee. Similarly, using 3e as chiral ligand, enantioselective arylation and alkynylation of aldehydes also proceeded readily, leading to the desired chiral alcohols in up to 92% isolated yield at 99% ee and 80% isolated yields and up to 84% ee, respectively. The current work would shed light on expanding the structure diversity in the design of chiral ligands and chiral catalysts.
- Gao, En,Li, Qiao,Duan, Lili,Li, Lin,Li, Yue-Ming
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supporting information
(2020/10/20)
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- Binaphthyl-based chiral ligands: Design, synthesis and evaluation of their performance in enantioselective addition of diethylzinc to aromatic aldehydes
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The design strategy and the performance of binaphthyl-based chiral ligands were evaluated with computation and enantioselective addition of diethylzinc to aromatic aldehydes. Under optimized conditions, enantioselective addition of diethylzinc to aromatic aldehydes provided the desired optically active secondary alcohols in high isolated yields (up to 91%) and excellent enantiomeric excesses (up to 98% ee).
- Yao, Chao,Wu, Piao,Huang, Yue,Chen, Yaoqi,Li, Lin,Li, Yue-Ming
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supporting information
p. 9712 - 9725
(2020/12/28)
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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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- Chiral P,N-ligands for the highly enantioselective addition of diethylzinc to aromatic aldehydes
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A new sterically hindered chiral P,N-ligand was synthesized and successfully applied to copper catalyzed asymmetric addition of diethylzinc to aromatic aldehydes. Various aromatic aldehydes can react smoothly to give the corresponding addition products with good to excellent enantioselectivities, which provides a readily accessible method for the preparation of chiral secondary alcohols.
- Wang, Qiang,Li, Shuang,Hou, Chuan-Jin,Chu, Ting-Ting,Hu, Xiang-Ping
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- Enantioselective addition of diethylzinc to aldehydes catalyzed by 5-cis-substituted proline derivatives
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5-Cis-substituted prolinols, prolinamines, and prolinamine sulfonamides proved to be efficient ligands for the enantioselective addition of diethylzinc to aldehydes, providing up to 99% ee. The sense of asymmetric induction can be controlled by the nature
- Prause, Felix,Wagner, Stefan,Breuning, Matthias
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- Chiral zinc amidate catalyzed additions of diethylzinc to aldehydes
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A series of bifunctional spiro ligands bearing “carboxamide–phosphine oxide” groups and ethylzinc carboxamidates from these ligands as catalysts for Et2Zn additions to aldehydes were reported. Excellent yields were obtained with moderate ee′s in Et2Zn additions to benzaldehyde derivatives, implying effectiveness of our newly designed catalytic structures as well as mediocre stereocontrol by these chiral ligands. Possible transition states were suggested based on the crystal structures of two ligands.
- Zhang, Jinxia,Li, Shasha,Zheng, Xinxin,Li, Hongjie,Jiao, Peng
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supporting information
p. 1913 - 1917
(2019/06/24)
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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 C2-symmetric six-membered carbene ligands for asymmetric diethylzinc addition of arylaldehydes
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A series of new six-membered NHC precursors were prepared by simply esterification of their parent compounds. Their applicability in asymmetric diethylzinc addition of arylaldehydes has been demonstrated and the corresponding secondary alcohol was obtained with good yields and moderate enantioselectivities. (Figure pressented)
- Zhou, Bihui,Li, Zijing,Yang, Chen,Li, Linlin,Fan, Limei,Huang, Hongxia,Li, Jie
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- Chiral thiazolidines in the enantioselective ethylation of aldehydes: An experimental and computational study
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A library of new chiral thiazolidines was prepared starting from L-cysteine and D-penicillamine in a simple, one-step procedure. 2-Arylthiazolidines were obtained, as diastereoisomeric mixtures, with good yields and in short reaction times, through a new and greener procedure, using microwave irradiation. Their use as chiral ligands in the enantioselective ethylation of aromatic aldehydes was studied and optimized, originating good to excellent conversions and ee up to 94% in 6 h. A series of heteroaromatic and aliphatic substrates were also enantioselectively ethylated with success, with ee up to 77%. The distinct opposite chirality in L-cysteine and D-penicillamine makes the use of these ligands an interesting approach for obtaining both the (S) and (R) enantiomers of the chiral alcohols, compounds with potential applications in the area of fine chemistry. NMR studies were carried out using a diastereoisomeric mixture of thiazolidines, allowing the identification of the most stable structure. Computational studies confirmed this result and also gave important insight into the species involved in the catalytic cycle of the enantioselective alkylation.
- Tavares, Nélia C.T.,Neves, César T.,Milne, Bruce F.,Murtinho, Dina,Pais, Alberto A.C.C.,Serra, M. Elisa Silva
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- Enantioselective addition of organozinc reagents to carbonyl compounds catalyzed by a camphor derived chiral γ-amino thiol ligand
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In this article, the design and synthesis of the chiral camphor derived γ-amino thiol ligand 17 and its application in catalytic enantioselective carbon-carbon forming reactions through the addition of organozinc reagents to carbonyl compounds is described. The catalytic activity and enantioselectivity of ligand 17 is demonstrated in the enantioselective addition of various organozinc reagents to aldehydes and ketoesters, offering the corresponding alcohols in high yields and enantioselectivities. The role of the mercapto group in the highly enantioselective 1,2-addition reaction of organozincs to aldehyde is also discussed.
- Wu, Hsyueh-Liang,Wu, Ping-Yu,Cheng, Ying-Ni,Uang, Biing-Jiun
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p. 2656 - 2665
(2016/05/10)
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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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- 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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- Design of novel chiral N,N,O-tridentate phenanthroline ligands and their application to enantioselective addition of organozinc reagents to aldehydes
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The novel N,N,O-tridentate phenanthroline ligand (BinThro) bearing an axially chiral binaphthyl backbone prepared from BINOL was found to be an effective chiral catalyst for enantioselective addition of diethylzinc to aromatic aldehydes with high enantios
- Naganawa, Yuki,Namba, Tomoya,Aoyama, Tomotaka,Shoji, Kentaro,Nishiyama, Hisao
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p. 13224 - 13227
(2015/05/20)
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- Efficient asymmetric addition of diethylzinc to aldehydes using C 2-novel chiral pyridine β-amino alcohols as chiral ligands
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A series of novel C2-symmetric chiral pyridine β-amino alcohol ligands have been synthesized from 2,6-pyridine dicarboxaldehyde, m-phthalaldehyde and chiral β-amino alcohols through a two-step reaction. All their structures were characterized by 1H NMR, 13C NMR and IR. Their enantioselective induction behaviors were examined under different conditions such as the structure of the ligands, reaction temperature, solvent, reaction time and catalytic amount. The results show that the corresponding chiral secondary alcohols can be obtained with high yields and moderate to good enantiomeric excess. The best result, up to 89% ee, was obtained when the ligand 3c (2S,2R)-2,2-((pyridine-2,6-diylbis(methylene)) bisazanediyl))bis(4-methyl-1,1-diphenylpentan-1-ol) was used in toluene at room temperature. The ligand 3g (2S,2R)-2,2-((1,3-phenylenebis(methylene)) bis(azanediyl))bis(4-methyl-1,1-diphenylpentan-1-ol) was prepared in which the pyridine ring was replaced by the benzene ring compared to 3c in order to illustrate the unique role of the N atom in the pyridine ring in the inductive reaction. The results indicate that the coordination of the N atom of the pyridine ring is essential in the asymmetric induction reaction. Copyright
- Zhang, Weijie,Tang, Ruiren,Yu, Huirong,Gao, Shu
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p. 545 - 551
(2014/07/07)
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- Insights into the asymmetric heterogeneous catalysis in porous organic polymers: Constructing A TADDOL-Embedded chiral catalyst for studying the structure-activity relationship[ ]
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Construction of porous organic polymers (POPs) as asymmetric catalysts remains as an important but challenging task. Herein, we exploit the "bottom-up" strategy to facilely synthesize an α,α, α,α-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL)-based chiral porous polymer (TADDOL-CPP) for highly efficient asymmetric catalysis. Constructed through the covalent linkages among the three-dimensional rigid monomers, TADDOL-CPP possesses hierarchical porous structure, high Brunauer-Emmett-Teller (BET) surface area, together with abundant and uniformly-distributed chiral sites. In the presence of [Ti(OiPr)4], TADDOL-CPP acts as a highly efficient and recyclable catalyst in the asymmetric addition of diethylzinc (Et2Zn) to aromatic aldehydes. Based on the direct observation of the key intermediates, the reaction mechanism has been revealed by solid-state 13C magic-angle spinning (MAS) NMR spectroscopy. In combination with the catalytic testing results, characterization on the working catalyst provides further information for understanding the structure-activity relationship. We suggest that the catalytic activity of TADDOL-CPP is largely affected by the structural rigidity, cooperative catalysis, local chiral environment, and hierarchical porous framework. We expect that the information obtained herein will benefit to the designed synthesis of robust POP catalysts toward practical applications.
- An, Wan-Kai,Han, Man-Yi,Wang, Chang-An,Yu, Si-Min,Zhang, Yuan,Bai, Shi,Wang, Wei
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supporting information
p. 11019 - 11028,10
(2014/12/09)
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- Asymmetric preparation of new N, N -dialkyl-2-amino-1,1,2-triphenylethanol catalysts and a kinetic resolution in the addition of diethylzinc to flavene-3-carbaldehydes
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Enantiopure N,N-dialkyl-(S)-2-amino-1,1,2-triphenylethanols were prepared using a new synthetic methodology and tested for their ability to catalyze the enantioselective addition of diethylzinc to aldehydes. The structural modification of N-substituents of the catalysts led us to identify N-methyl-N-(S)-1-phenyl-ethyl-substituted 4d as an effective catalyst for the addition. Also disclosed is a kinetic resolution of racemic flavene-3- carbaldehydes with the chiral catalyst.
- Kang, Seockyong,Baek, Jinho,Ko, Yikyung,Im, Chan,Park, Yongsun
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supporting information
p. 630 - 634
(2013/04/23)
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- C2 symmetrical nickel complexes derived from α-amino amides as efficient catalysts for the enantioselective addition of dialkylzinc reagents to aldehydes
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A series of C2 symmetrical 1:2 Ni:L complexes derived from α-amino amides were studied for the enantioselective addition of dialkylzinc reagents to aldehydes. Different structural elements on the ligands seem to play an important role in determining the observed enantioselectivity. Through optimization of structure and reaction conditions, the best ligand provided secondary alcohols in excellent yields (up to 98%) and enantioselectivity of up to 99% ee for (R)-enantiomer. A transition state model has been proposed to explain the observed enantioselectivities based on computational calculations at the DFT level. Very interestingly, calculations suggest a coordination model of the aldehyde to the metal complex through association of a lone pair of the carbonyl oxygen to the hydrogen atom of an amino group.
- Escorihuela, Jorge,Altava, Belen,Burguete, M. Isabel,Luis, Santiago V.
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p. 551 - 558
(2013/07/27)
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- Enantioselective addition of dialkylzincs to aldehydes catalyzed by (-)-MITH
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An effective catalytic system that imparts high enantioselectivity has been disclosed for the synthesis of optically active alcohols, which may undergo further chemical transformations. The enantioselective alkylation of aldehydes with dialkylzincs to afford the corresponding optically active alcohols with excellent enantioselectvities has been achieved in the presence of 0.1-0.5 mol % of the camphor-derived chiral ligand (-)-2-exo-morpholinoisobornane-10-thiol (MITH) (1) at room temperature or at 0 °C. I zinc so too: The enantioselective alkylation of aldehydes with dialkylzincs yielded the desired alcohol products with up to 99 % ee in the presence of 0.1-0.5 mol % of ligand (-)-2-exo-morpholinoisoborne-10-thiol (1) at room temperature or at 0°C. Copyright
- Cheng, Ying-Ni,Wu, Hsyueh-Liang,Wu, Ping-Yu,Shen, Ying-Ying,Uang, Biing-Jiun
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supporting information
p. 2921 - 2924
(2013/02/22)
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- CAMPHOR-DERIVED COMPOUNDS, METHOD FOR MANUFACTURING THE SAME, AND APPLICATION THEREOF
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Camphor-derived compounds are disclosed, which are represented as the following formula (I): wherein R1, R2, R3, and R4 each are defined as described in the specification. In addition, a method for manufacturing the camphor-derived compounds and application thereof are disclosed.
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Page/Page column 13-14
(2012/04/05)
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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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- 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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- Switching of enantioselectivity in the catalytic addition of diethylzinc to aldehydes by regioisomeric chiral 1,3-amino sulfonamide ligands
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Twenty chiral 1,3-amino sulfonamides of two classes (2a-i and 3a-k) have been prepared from (-)-cis-2-benzamidocyclohexanecarboxylic acid (1) and studied as ligands for catalytic enantioselective addition of Et2Zn to a variety of aromatic and aliphatic aldehydes. The ligands 2 and 3 are regioisomers in which the position of the amine and sulfonamide groups is exchanged. Each class of ligands with the same chirality was shown to afford sec-alcohols with the opposite stereochemistry. Structural surveys revealed that the combination of tertiary amino and p-toluenesufonylamido groups works most effectively for the reaction. Through optimization of the structural and reaction conditions, the best ligands quantitatively provided both enantiomeric secondary alcohols in good to excellent enantioselectivity of up to 94% and 98% ee for (S)- and (R)-enantiomers, respectively.
- Hirose, Takuji,Sugawara, Kazuyuki,Kodama, Koichi
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experimental part
p. 5413 - 5428
(2011/08/05)
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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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- Synthesis of sterically constrained tricyclic pyrrolidinyl alcohol ligands for the enantioselective ethylation of aryl aldehydes: Assessment of the influence of ring strain and N-alkyl chain length on asymmetric induction
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A series of chiral sterically constrained tricyclic pyrrolidinyl alcohol ligands were synthesized from the appropriate amino acids, and a comparative study of the activity and selectivity of the ligands for the enantioselective ethylation of aromatic aldehydes was carried out. The results obtained were compared with those previously reported for related monocyclic analogues; it was found that the bicyclo[2.2.2]octane backbone fused to pyrrolidine and the groups attached to the carbinol centre, as well as the chain length of the β-amino alcohol, had a marked effect on the enantioselectivity. The enantioselective addition of dialkylzincs to aryl aldehydes in the presence of ligands with diethyl substituents on the carbinol carbon afforded (R)-sec-alcohols in up to 99% enantiomeric excess (ee).
- Sahin, Engin,Kilic, Hamdullah
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experimental part
p. 277 - 282
(2011/05/17)
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- CAMPHOR-DERIVED BETA-AMINO ALCOHOL COMPOUNDS, METHOD FOR MANUFACTURING THE SAME AND ASYMMETRIC ADDITION OF ORGANOZINC TO ALDEHYDES USING THE SAME
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A novel camphor-derived β-amino alcohol compound is disclosed. The novel camphor-derived β-amino alcohol compound can be used in asymmetric addition of organozinc to aromatic and aliphatic aldehydes, including linear aliphatic ones, thus generating corresponding secondary alcohols in high yields and enantiomeric excess.
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Page/Page column 8
(2012/01/13)
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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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- 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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- Synthesis of chiral 1,3-disubstituted tetrahydroisoquinolines and their use in the asymmetric addition of diethylzinc to aldehydes
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The effects of modifications on three sites of 1-(1,2,3,4-tetrahydro- isoquinolin-1 -yl)-naphthalen-2-ol (THIQNOL) chiral ligands the asymmetric diethylzinc additions were examined. The studies showed that modifications at the nitrogen only reduce the eff
- MacLeod, Patricia D.,Reckling, Amy M.,Li, Chao-Jun
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experimental part
p. 1319 - 1337
(2010/10/20)
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- A BINOL-terpyridine-based multi-task catalyst for a sequential oxidation and asymmetric alkylation of alcohols
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Treatment of a BINOL-terpyridine compound with RuCl3 generates a Ru(II) complex (R)-6. This complex is found to be a novel multi-task catalyst capable of conducting a sequential oxidation and asymmetric alkyl addition to convert primary alcohols to chiral secondary alcohols. The terpyridine-Ru(II) site of (R)-6 catalyzes an efficient oxidation of primary alcohols to aldehydes which then undergo an enantioselective alkylation to generate chiral secondary alcohols when the BINOL site of (R)-6 is combined with ZnEt2 and Ti(OiPr)4.
- Chen, Xi,Liu, Qiang,Sun, Hong-Bao,Yu, Xiao-Qi,Pu, Lin
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scheme or table
p. 2345 - 2347
(2010/06/13)
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- Structurally constrained C1-1,1′-bisisoquinoline-based chiral ligands: geometrical implications on enantioinduction in the addition of diethylzinc to aldehydes
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New highly constrained chiral C1-1,1′-bisisoquinoline ligands have been synthesized. X-ray crystallographic analysis of these ligands showed peculiar structural differences between the parent 1′,2′,3′,4′-tetrahydro-1,1′-bisisoquinolin e and its alkyl, acyl and sulfonyl derivatives. The consequences of their geometrical conformations on enantioinduction were examined by employing the enantioselective addition of diethylzinc to aldehydes. Such conformations greatly affected the catalytic efficiency of these ligands.
- Qi, Gao,Judeh, Zaher M.A.
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experimental part
p. 429 - 436
(2010/07/02)
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- Synthesis and application of 3-substituted (S)-binol as chiral ligands for the asymmetric ethylation of aldehydes
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A series of (S)-BINOL ligands substituted at the 3 position with some five-membered nitrogen-containing aromatic heterocycles were effectively prepared and their catalytic abilities were evaluated in the asymmetric addition of diethylzinc to benzaldehyde in the presence of titanium tetraisopropoxide. Under the optimized reaction conditions, titanium complex of (S)-3-(1H-benzimidazol-1-yl)-1,1′-bi-2-naphthol was found to be the most efficient catalyst for asymmetric ethylation of various aldehydes to generate the corresponding secondary alcohols in up to 99% yield and 91% ee.
- Zhang, Zhi-Guang,Dong, Zhi-Bing,Li, Jin-Shan
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experimental part
p. 820 - 826
(2010/11/21)
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- (R)-(+)-binol-functionalized mesoporous organosilica as a highly efficient pre-chiral catalyst for asymmetric catalysis
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(R)-(+)-Binol-functionalized chiral periodic mesoporous organosili-cas (PMOs) with different framework compositions were successfully synthesized by cocondensation of (R)-2,2′-di(methoxymethyl)oxy-6,6'-di(1-propyl- trimethoxysilyl)-1,1'-binaphthyl (BSBi-n
- Liu, Xiao,Wang, Peiyuan,Yang, Yan,Wang, Peng,Yang, Qihua
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scheme or table
p. 1232 - 1239
(2011/07/08)
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- Dual stereoselectivity in the dialkylzinc reaction using (-)-β-pinene derived amino alcohol chiral auxiliaries
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(+)-Nopinone, prepared from naturally occurring (-)-β-pinene, was converted to the two regioisomeric amino alcohols 3-MAP and 2-MAP in very good yield and excellent isomeric purity. Amino alcohol 3-MAP was synthesized by converting (+)-nopinone to the corresponding α-ketooxime. This was reduced to the primary amino alcohol and was converted to the morpholino group through a simple substitution reaction. 3-MAP was characterized by X-ray crystallography, which displayed the rigidity of the pinane framework. Amino alcohol 2-MAP was prepared from its trans isomer 2, which in tum was synthesized via hydroboration/ oxidation of the morpholine enamine of (+)-nopinone. Two-dimensional NMR was used to characterize amino alcohol 2-MAP, and NOE was used to confirm its relative stereochemistry. These amino alcohols were employed as chiral auxiliaries in the addition of diethylzinc to benzaldehyde to obtain near-quantitative asymmetric induction in the products. The use of 3-MAP yielded (S)-phenylpropanol in 99% ee, and its regioisomer 2-MAP gave the opposite enantiomer, (R)-phenylpropanol, also in 99% ee. Other aromatic, aliphatic, and α,β-unsaturated aldehydes were implemented in this method, affording secondary alcohols in high yield and enantiomeric excess. Amino alcohols 2-MAP and 3-MAP were also found to be useful in the dimethylzinc addition reaction, both catalyzing the addition to benzaldehyde with nearly quantitative ee. Regioisomeric amino alcohols 2-MAP and 3-MAP, even though they were prepared from one enantiomer of nopinone, provide antipodal enantiofacial selectivity in the dialkylzinc addition reaction. This circumvents the necessity to synthesize amino alcohols derived from (-)-nopinone, which in tum requires the unnatural (+)-β-pinene. Possible mechanistic insights are offered to explain the dual stereoselectivity observed in the diethylzinc addition reaction involving regioisomeric, pseudo-enantiomeric amino alcohols 3-MAP and 2-MAP.
- Binder, Caitlin M.,Bautista, April,Zaidlewicz, Marek,Krzeminski, Marek P.,Oliver, Allen,Singaram, Bakthan
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supporting information; experimental part
p. 2337 - 2343
(2009/08/07)
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- Asymmetric addition of diethylzinc to aldehydes catalyzed by a camphor-derived β-amino alcohol
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The asymmetric addition of diethylzinc to aromatic and aliphatic aldehydes, including linear aliphatic ones, catalyzed by 2 mol % of β-amino alcohol (1S, 2R)-7,7-dimethyl-1-morpholin-4-yl-bicyclo[2.2.1]heptan-2-ol 10 gave the corresponding secondary alcohols in high yields and with up to 94% ee at ambient temperature after 15 min.
- Wu, Zhi-Long,Wu, Hsyueh-Liang,Wu, Ping-Yu,Uang, Biing-Jiun
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experimental part
p. 1556 - 1560
(2009/11/30)
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- Enantioselective addition of diethylzinc to aromatic aldehydes catalyzed by Ti(IV) complexes of C2-symmetrical chiral BINOL derivatives
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Enantioselective addition of diethylzinc to a series of aromatic aldehydes is developed using new chiral C2-symmetric ligand (S)-2,2′-(1,1′-binaphthyl-2,2′-diylbis(oxy))bis(methyl ene)bis(4-nitrophenol) (S)-2b. The catalytic system employing 10 mol % of (S)-2b and 120 mol % of Ti(OiPr)4 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 89% ee and up to 95% yield of the corresponding secondary alcohol under mild conditions.
- Gou, Shaohua,Judeh, Zaher M.A.
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scheme or table
p. 281 - 283
(2009/04/11)
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- Synthesis of novel chiral tridentate aminophenol ligands for enantioselective addition of diethylzinc to aldehydes
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Novel chiral tridentate aminophenol ligand (S)-3a was obtained by a Mannich-type reaction of cresol, paraformaldehyde, and (S)-1-(2-methoxyphenyl)-2-methylpropan-1-amine followed by a deprotection step. This tridentate aminophenol ligand shows high yield and enantioselectivity in the diethylzinc additions to a broad range of substrates, including alkyl, aryl, and α,β-unsaturated aldehydes.
- Yang, Xiao-Feng,Hirose, Takuji,Zhang, Guang-You
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p. 1670 - 1675
(2008/12/20)
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- Practical and highly enantioselective alkylation of aldehydes catalyzed by a titanium complex of 3-aryl H8-BINOL
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A titanium complex derived from 3-(3,5-diphenylphenyl)-H8-BINOL exhibits high catalytic activity and enantioselectivity in the alkylation of aldehydes. Enantioselectivities comparable to or higher than 20 mol % of the parent H8-BINOL
- Harada, Toshiro,Ukon, Takahiro
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p. 2499 - 2502
(2008/03/15)
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- Enantioselective diethylzinc addition to aldehydes catalyzed by Ti(IV) complex of unsymmetrical chiral bis(sulfonamide) ligands of trans-cyclohexane 1,2-diamine
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Titanium(IV) complexes of bidentate trans-cyclohexane 1,2-diamine-based unsymmetrical chiral bis(sulfonamide) ligands were evaluated as catalysts for the asymmetric addition of diethylzinc to aldehydes. The reaction provided secondary alcohols in quantita
- Bisai, Alakesh,Singh, Pradeep K.,Singh, Vinod K.
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p. 598 - 601
(2007/10/03)
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- Novel polymer-supported chiral catalysts for the asymmetric addition of diethylzinc to aldehydes
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Newly synthesized polymer-supported chiral amino alcohol catalysts 5a and 5b have been proved to be effective for the enantioselective addition of diethylzinc to aldehydes, affording the corresponding sec-alcohols in moderate enantiomeric excesses with good to excellent yields. The recycled catalyst could be reused in the same reaction without significant deterioration in performance.
- Wang, Su-Xi,Chen, Fen-Er
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p. 1011 - 1013
(2008/02/13)
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- Synthesis of a new 1,4-aminoalcohol and its use as catalyst in the enantioselective addition of organozinc to aldehydes
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The synthesis of a new enantiopure, conformationally constrained 1,4-aminoalcohol is reported, starting from commercially available reagents from the chiral pool. This 1,4-aminoalcohol was used as chiral ligand in the addition of Et2Zn to aldehydes (best ee 98%) and in the synthesis of chiral propargylic alcohols (best ee 70%) by alkynylzinc species.
- Scarpi, Dina,Galbo, Fabrizio Lo,Guarna, Antonio
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p. 1409 - 1414
(2007/10/03)
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- Polystyrene-supported (R)-2-piperazino-1,1,2-triphenylethanol: A readily available supported ligand with unparalleled catalytic activity and enantioselectivity
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(Chemical Equation Presented) A very active and highly enantioselective catalytic resin, designed for minimal perturbation of the catalytic center by the polymer matrix, has been assembled in two steps from (S)-triphenylethylene oxide, piperazine, and Merrifield resin and tested in the enantioselective ethylation of aldehydes. 1-Arylpropanols of 94-95% ee are obtained in high yield by the use of only 2 mol % of catalytic resin at 0°C for 4 h.
- Castellnou, David,Sola, Lluis,Jimeno, Ciril,Fraile, Jose M.,Mayoral, Jose A.,Riera, Antoni,Pericas, Miquel A.
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p. 433 - 438
(2007/10/03)
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- Polystyrene-supported amino alcohol ligands for the heterogeneous asymmetric addition of phenyl zinc reagents to aldehydes
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A family of polystyrene-supported amino alcohols, characterized by a high catalytic activity in alkyl transfer from zinc to formyl groups has been successfully tested in the enantioselective addition of phenyl zinc reagents to aldehydes to afford chiral diarylmethanols. Enantioselectivities higher than 90% (mean ee 90.5%; eight examples) are recorded with aromatic aldehydes in what represents the first successful use of heterogeneous, polymeric reagents for enantiocontrol in the phenylation of aldehydes.
- Castellnou, David,Fontes, Montserrat,Jimeno, Ciril,Font, Daniel,Solà, Lluís,Verdaguer, Xavier,Pericàs, Miquel A.
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p. 12111 - 12120
(2007/10/03)
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- Enantioselective addition of diethylzinc to aldehydes using 1,4-aminoalcohols as chiral ligands
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Conformationally constrained, optically active 1,4-aminoalcohols have been used as chiral ligands in the addition of diethylzinc to aromatic aldehydes. The enantioselectivity was strongly influenced by the N-alkyl group: the best results were achieved wit
- Scarpi, Dina,Lo Galbo, Fabrizio,Occhiato, Ernesto G.,Guarna, Antonio
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p. 1319 - 1324
(2007/10/03)
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- A convenient synthesis of piperidine-based β-amino alcohols from L-Phe and highly enantioselective addition of diethyl zinc to aldehydes
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β-Amino alcohols 4a-e were easily prepared from L-phenylalanine in three simple straightforward steps. The key intermediate compound (S)-3 was achieved in high yield (up to 92%) with glutaraldehyde and NaBH4/H2SO4 in THF at room temperature. These five ligands were applied to catalyze enantioselective addition of diethyl zinc to aldehydes, high asymmetric induction was observed with 4c and 4e, and the ee value was up to 98%. The effect of the substitutes on the nitrogen atom was also observed via comparing piperidine-based amino alcohols with pyrrolidine-based similar ligands.
- Da, Chao-Shan,Han, Zhi-jian,Ni, Ming,Yang, Fan,Liu, Da-Xue,Zhou, Yi-Feng,Wang, Rui
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p. 659 - 665
(2007/10/03)
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- Effect of spacers on the activity of soluble polymer supported catalysts for the asymmetric addition of diethylzinc to aldehydes
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A chiral Zn(II)-salen complex tethered with poly(ethylene glycol) (PEG) was synthesized. This soluble polymer-supported complex was found to catalyze the asymmetric addition of diethylzinc to a series of aromatic aldehydes in good yields and with good ena
- Anyanwu, Uche K.,Venkataraman
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p. 6445 - 6448
(2007/10/03)
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- An amino alcohol ligand for highly enantioselective addition of organozinc reagents to aldehydes: Serendipity rules
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(matrix presented) Amino alcohol 4 (or its enantiomer) is prepared in two simple steps. Commercial (1R,2S)-2-amino-1,2-diphenylethanol is dialkylated with bis(2-bromoethyl) ether. Subsequent hydrogenation over 5% Rh on alumina in the presence of morpholine unexpectedly stops at the hexahydro derivative 4. Amino alcohol 4 promotes the enantioselective addition of diethylzinc to aldehydes at room temperature in up to 99% enantiomeric excess.
- Nugent, William A.
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p. 2133 - 2136
(2007/10/03)
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- A purely synthetic, diversity amenable version of norephedrine thiols for the highly enantioselective diethylzinc addition to aldehydes
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A new β-aminothiol arising from purely synthetic yet enantiopure aminoalcohols has been prepared and successfully used in the addition of diethylzinc to aromatic aldehydes, yielding secondary alcohols in ee's up to 99%.
- Jimeno,Moyano,Pericàs,Riera
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p. 1155 - 1157
(2007/10/03)
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