- 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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- 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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- Iridium and Rhodium Complexes Containing Enantiopure Primary Amine-Tethered N-Heterocyclic Carbenes: Synthesis, Characterization, Reactivity, and Catalytic Asymmetric Hydrogenation of Ketones
-
The imidazolium salt [(S,S)-tBuNC3H3NCHPhCHPhNH2]PF6, (S,S)-11·HPF6 is a precursor to the enantiopure "Kaibene" ligand, tBu-Kaibene, (S,S)-11 featuring a tert-butyl group on the N-heterocyclic carbene (NHC) ring-nitrogen atoms. It has been prepared in high yield and purity by refluxing a chiral cyclic sulfamidate with 1-tert-butylimidazole. Similarly (S,S)-12·HPF6 with a mesityl group at the imidazolium ring-nitrogen atom has been prepared in the same fashion and serves as a source of Mes-Kaibene, (S,S)-12. These bidentate Kaibene ligands feature an NHC and a primary amine separated by a chiral linker. Salts (S,S)-11·HPF6 or (S,S)-12·HPF6 react with base and AgI or CuI to give a total of four M(Kaibene)2I compounds (M = Ag or Cu). At 22 °C, the amine-functionalized imidazolium cations undergo oxidative addition to iridium(I) in [IrCl(cod)]2 (cod = 1,5-cyclooctadiene) to generate iridium(III) hydride R-Kaibene compounds [IrHCl(cod)((S,S)-11)](PF6) (17) and [IrHCl(cod)((S,S)-12)](PF6) (18), respectively, each as a mixture of six configurational isomers. In contrast, the salt (S,S)-11·HPF6 reacts with [Ir(OtBu)(cod)]2 to produce a bimetallic iridium compound with (S,S)-11 as the bridging ligand. This compound contains interesting NH···Cl and NH···Ir noncovalent intramolecular interactions. Salt (S,S)-12·HPF6 reacts with silver oxide to yield [Ag2((S,S)-12)2](PF6)2 (20). Reagent 20 serves as an efficient transmetalation reagent to deliver to each rhodium in [RhCl(cod)]2 1 equiv of (S,S)-12 as a bidentate ligand to give [Rh(cod)((S,S)-12)](PF6). In the reaction between [IrCl(cod)]2 and 20, (S,S)-12 ends up coordinated in an iridium(III) hydride complex (22) as a tridentate ligand via the NHC, NH2, and a cyclometalated phenyl group. The two iridium hydride compounds, 18 and 22, are catalysts for the hydrogenation of a range of ketones (turnover number up to 499, turnover frequency up to 249 h-1, with er (enantiomeric ratio) up to 35:65 R:S).
- Wan, Kai Y.,Roelfes, Florian,Lough, Alan J.,Hahn, F. Ekkehardt,Morris, Robert H.
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supporting information
p. 491 - 504
(2018/02/17)
-
- Chiral thiazolidines in the enantioselective ethylation of aldehydes: An experimental and computational study
-
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 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 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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- 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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- 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
-
supporting information
p. 11019 - 11028,10
(2014/12/09)
-
- Vasicine as tridentate ligand for enantioselective addition of diethylzinc to aldehydes
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The first report of natural l-vasicine as tridentate chiral ligand for the enantioselective addition of diethylzinc to a variety of aliphatic and aromatic aldehydes is described. The ligand generates R-isomer of the secondary alcohols upto 98% ee. The qui
- Aga, Mushtaq A.,Kumar, Brijesh,Rouf, Abdul,Shah, Bhahwal A.,Taneja, Subhash C.
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supporting information
p. 2639 - 2641
(2014/05/06)
-
- 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
-
p. 2727 - 2729
(2014/05/06)
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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
-
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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- 2-Pyridylsulfinamides as effective catalysts in the asymmetric alkylation of aldehydes with diethylzinc Dedicated to Dr. N.N. Joshi, National Chemical Laboratory, Pune, India
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Chiral 2-pyridylsulfinamides were shown to be effective catalysts in the alkylation of aryl and alkyl aldehydes with diethylzinc providing the corresponding alcohols in excellent enantioselectivity. Sulfinamide catalysts possessing solitary chirality at the sulfur center produced the product phenethyl alcohol in good enantioselectivity. Diastereomeric sulfinamides possessing chirality at the carbon-bearing nitrogen and at the sulfur of the sulfinamide increased the enantioselectivity of the product alcohols up to >99%. However, there is no effect of the match-mismatch pair of sulfinamide diastereomers on the outcome of the chiral induction of the product phenethyl alcohols. It was conclusively proved that chirality at the sulfur center is mandatory for obtaining good enantioselectivity in the reaction.
- Prasad, Kavirayani R.,Revu, Omkar
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p. 8422 - 8428
(2013/09/02)
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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
-
experimental part
p. 768 - 781
(2012/08/27)
-
- Click-BINOLs: A new class of tunable ligands for asymmetric catalysis
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A new class of easily tunable 1,2,3-triazole-BINOL ligands, 'click'-BINOLs, have been synthesized from readily available alkynes and several azido-BINOL derivatives using the powerful Huisgen [3+2] cycloaddition 'click' approach. The activity of these ligands in asymmetric Lewis acid catalysis has been explored for the first time in the diethylzinc addition to aldehydes. The C 2-symmetric ligand 1d showed an interesting catalytic behavior, which suggests the non-innocent participation of the triazole units. Thus, good enantioselectivities (up to 86% ee) were obtained by both the right selection of the substitution pattern at the triazole ring and the fine tuning of the reaction conditions. Georg Thieme Verlag Stuttgart New York.
- Beckendorf, Stephan,Mancheno, Olga Garcia
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experimental part
p. 2162 - 2172
(2012/10/07)
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- Ar-BINMOLs with axial and sp3 central chirality - Characterization, chiroptical properties, and application in asymmetric catalysis
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2′-Hydroxy-1,1′-binaphthalene-2-(arylmethanol) (Ar-BINMOLs), a family of new 1,1′-binaphthalene-2,2′-diol derivatives, prepared by a [1,2]-Wittig rearrangement, are introduced as new chiral molecules for the study of the modes of supramolecular aggregatio
- Gao, Guang,Bai, Xing-Feng,Yang, Hua-Meng,Jiang, Jian-Xiong,Lai, Guo-Qiao,Xu, Li-Wen
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supporting information; experimental part
p. 5039 - 5046
(2011/10/09)
-
- 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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- 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)
-
- 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)
-
- 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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- 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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- 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)
-
- 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 aromatic aldehydes catalysed by titanium(IV)-bis-BINOLate-2′,2″-propylether complexes: An inside view of the catalytic active species
-
1H NMR, CD, ESI-MS and PM6 calculation were used to investigate the nature of the catalytic active species, using bis-BINOLate-2′, 2″-propylether-titanium complexes in ethylation of aldehdyes.
- Abreu, Artur R.,Loureno, Mirtha,Peral, Daniel,Rosado, Mário T.S.,Eusébio, Maria E.S.,Palacios, Scar,Bayón, J. Carles,Pereira, Mariette M.
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experimental part
p. 91 - 97
(2010/10/01)
-
- Enantioselective addition of diethylzinc to aldehydes catalyzed by d-glucosamine derivatives: Highly pronounced effect of trifluoromethylsulfonamide
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We present the synthesis of β-hydroxy sulfonamides derived from d-glucosamine and their application as ligands in titanium tetraisopropoxide promoted enantioselective addition of diethylzinc to benzaldehyde and selected aromatic and aliphatic aldehydes. The N-trifluoromethylosulfonamido-d-glucosamine derivative is one of the most active ligands known and only 1 mol% of the ligand is sufficient for efficient catalysis of diethylzinc addition. The reaction is highly enantioselective for some aromatic aldehydes and enantiomeric excess up to 99% was obtained.
- Bauer, Tomasz,Smoliński, S?awomir
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experimental part
p. 247 - 251
(2010/11/18)
-
- (R)-(+)-binol-functionalized mesoporous organosilica as a highly efficient pre-chiral catalyst for asymmetric catalysis
-
(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)
-
- A BINOL-terpyridine-based multi-task catalyst for a sequential oxidation and asymmetric alkylation of alcohols
-
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)
-
- Rapid screening for asymmetric catalysts: The efficient connection of two different catalytic asymmetric reactions
-
A screening method for asymmetric catalysts is reported in which a metal-containing optically-active product of an asymmetric reaction is employed as a chiral catalyst in another asymmetric reaction; the rapid preparation and instant testing system of cat
- Yoshida, Kazuhiro,Toyoshima, Takeharu,Akashi, Naohisa,Imamoto, Tsuneo,Yanagisawa, Akira
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supporting information; experimental part
p. 2923 - 2925
(2009/11/30)
-
- Synthesis of chiral sulfamide-amine alcohol ligands for enantioselective alkylation of aldehydes
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A series of chiral sulfamide-amine alcohols (SAA) (1-6) has been easily synthesized from commercially available chiral amino alcohols. In the absence of Ti(OiPr)4, ligand 4 catalyzed the asymmetric addition of diethylzinc to aromatic aldehydes with moderate to good yields and enantioselectivities.
- Mao, Jincheng
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experimental part
p. 3710 - 3721
(2009/12/24)
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- Efficient one-step synthesis of chiral bidentate oxazoline-alcohol ligands via a cyclic imidate ester rearrangement
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Various chiral bidentate oxazoline-alcohol ligands were obtained in a straightforward one-step synthesis via a cyclic imidate ester rearrangement. These chiral ligands were tested and compared in asymmetric diethylzinc additions to aldehydes resulting in
- Noel, Timothy,Robeyns, Koen,Meervelt, Luc Van,Eycken, Erik Van der,Eycken, Johan Van der
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experimental part
p. 1962 - 1968
(2010/03/03)
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- Asymmetric reduction of halo-substituted arylalkanones with Rhizopus arrhizus
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The Rhizopus arrhizus-mediated asymmetric reduction of various haloaryl alkanones furnished the respective (S)-carbinols with good to excellent enantioselectivities. It was found that the reaction course was primarily governed by the relative position of the halogen with respect to the carbonyl group, and its size. The relative order of efficacies of the nature of the halogen and their substitution pattern were Br > Cl > F and o- > p- > m-. The ortho-effect was the most predominant factor in the stereochemical outcome of the reaction, which was also confirmed with some non-halo-substituted acetophenones.
- Salvi, Neeta A.,Chattopadhyay, Subrata
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p. 1992 - 1997
(2008/12/22)
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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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- Chiral aryl pyridyl alcohols as enantioselective catalysts in the addition of diethylzinc to substituted benzaldehydes
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Chiral (5-aryl-10,10-dimethyl-6-aza-tricyclo[7.1.1.02,7]undeca- 2(7),3,5-trien-8-yl)-diphenyl-methanols were prepared from highly enantiopure (1R)-(+)-α-pinene (> 97% ee), and applied in the enantioselective addition of diethylzinc to substitut
- Chang, Tien-Chu,Chen, Chinpiao
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experimental part
p. 606 - 615
(2009/05/11)
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- Synthesis of new chiral cis-3-hydroxyazetidines and their application in diethylzinc addition to aldehydes
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A new series of chiral cis-3-hydroxyazetidines have been prepared from (R)-1-phenylethylamine. They have excellent catalytic activities and enantiomeric selectivities in asymmetric addition of diethylzinc to aromatic aldehydes.
- Zhang, Zhanbin,Li, Min,Zi, Guofu
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p. 802 - 808
(2013/08/22)
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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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- Synthesis of novel chiral 1,3-aminophenols and application for the enantioselective addition of diethylzinc to aldehydes
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Novel chiral 1,3-aminophenols were efficiently synthesized by applying a Friedel-Crafts reaction and optical resolution. The catalytic activity of the aminophenols was studied for the addition of diethylzinc to benzaldehyde. The results showed that (S)-5a with bulky tert-butyl groups on the stereogenic carbon atom and 4,6-positions of phenol favored higher enantioselectivity (94% ee). The same ligand was also used with other aldehydes, to give optically active alcohols in good chemical yields and ee values (up to 99%).
- Yang, Xiao-Feng,Wang, Zhao-Hui,Koshizawa, Tomoaki,Yasutake, Mikio,Zhang, Guang-You,Hirose, Takuji
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p. 1257 - 1263
(2008/02/04)
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- The effect of direct steric interaction between substrate substituents and ligand substituents on enantioselectivities in asymmetric addition of diethylzinc to aldehydes catalyzed by sterically congested ferrocenyl aziridino alcohols
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The direct strong steric interaction between substrate substituents and ligand substituents was first discovered in asymmetric addition of diethylzinc to aldehydes catalyzed by sterically congested ferrocenyl aziridino alcohol derivatives. In addition, th
- Wang, Min-Can,Hou, Xue-Hui,Chi, Chao-Xian,Tang, Ming-Sheng
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p. 2126 - 2132
(2007/10/03)
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- Immobilization of a BINOLate-titanium catalyst by use of aggregation phenomenon
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Upon treatment with titanium tetraisopropoxide, tris-BINOL with a rigid aromatic tether forms an insoluble polymeric aggregate, which shows a catalytic activity in asymmetric addition of diethylzinc to aldehydes. Georg Thieme Verlag Stuttgart.
- Harada, Toshiro,Nakatsugawa, Masashi
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p. 321 - 323
(2007/10/03)
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- Synthesis and application of 3,3′-diarylmethyl BINOLs
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A new class of 3,3′-diarylmethyl BINOL derivatives were synthesized and applied to the catalytic asymmetric addition of diethylzinc to aldehydes. These chiral diol auxiliaries could be used as catalysts without the addition of Ti(i-PrO)4 and showed unprecedented catalytic activities and enantioselectivities (up to 94% ee, 5 mol% catalyst loading). Georg Thieme Verlag Stuttgart.
- Zhang, Yi-Li,Zhang, Feng,Tang, Wei-Jun,Wu, Qing-Lai,Fan, Qing-Hua
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p. 1250 - 1254
(2007/10/03)
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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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- α-Hydroxy carboxylic acids as ligands for enantioselective addition reactions of organoaluminum reagents to aromatic and aliphatic aldehydes
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The first examples of the enantioselective titanium-mediated trialkylaluminum additions to aromatic and aliphatic aldehydes catalyzed by optically active α-hydroxy acids are presented. The reactions proceed with very good yields and in good asymmetric induction. Enantioselectivities up to 92% are obtained depending on the ligand and aldehyde used. A stereochemical model for the reaction is proposed.
- Bauer, Tomasz,Gajewiak, Joanna
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p. 851 - 855
(2007/10/03)
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- Novel C2-symmetric 1,1′-disubstituted ferrocenyl aziridino alcohol ligands: Remarkable improvement of enantioselectivity in the catalytic asymmetric addition of diethylzinc to aldehydes
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A series of novel chiral C2-symmetric 1,1′-disubstituted ferrocenyl aziridino alcohols have been readily synthesized and applied as catalysts to promote enantioselective addition of diethylzinc to aldehydes affording the corresponding 1-propano
- Wang, Min-Can,Hou, Xue-Hui,Xu, Cui-Lian,Liu, Lan-Tao,Li, Gui-Lan,Wang, De-Kun
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p. 3620 - 3626
(2007/10/03)
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- Synthesis of a C2-symmetric chiral bipyridyldiol ligand and its application in the enantioselective addition of diethylzinc to substituted benzaldehydes
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Herein the synthesis of a novel C2-symmetric ligand comprising of a central bipyridine-pinene-derived core and two functionalized diphenylmethanol subunits is described. [8′-(Hydroxy-diphenyl-methyl)-10, 10,10′,10′-tetramethyl-[5,5′]bi[6-aza-tr
- Chen, Yi-Jing,Lin, Rong-Xin,Chen, Chinpiao
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p. 3561 - 3571
(2007/10/03)
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- Synthesis of chiral ferrocenyl aziridino alcohols and use in the catalytic asymmetric addition of diethylzinc to aldehydes
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A series of novel chiral ferrocenyl aziridino alcohols 5a-i were conveniently synthesized from l-serine and ferrocenecarboxaldehyde. These compounds have been used as chiral catalysts in the asymmetric addition of diethylzinc to aldehydes and the effects
- Wang, Min-Can,Liu, Lan-Tao,Zhang, Jun-Song,Shi, Yan-Yan,Wang, De-Kun
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p. 3853 - 3859
(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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