- Aluminum Complexes Based on Tridentate Amidoalkoxide NNO-Ligands: Synthesis, Structure, and Properties
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A series of novel NNO-type ligands 12a-17a, LH2, R1N(CH2CH2NHTs)CHR2CR3R4OH (R1 = Bn, R3 = R4 = H; R2 = H (12a), R2= (S)-Ph (13a), R2= (S)-Bn (14a), R2= (S)-i-Bu (15a); R1 = R2= (R)-Me, R3 = H, R4= (S)-Ph (16a); R1 = Bn, R2= (S)-i-Bu, R3 = R4 = Ph (17a)) was obtained; the ligands LH2 feature various degree of substitution, steric bulkiness, and chirality. Treatment of 11a (R1 = Me, R2 = R3 = R4 = H), 12a-17a, and 18a (R1 = Me, R2 = H, R3 = R4 = Ph) with AlMe3 afforded the complexes 11b-18b, [LAlMe]n (n = 1, 2). It was demonstrated that the structure of the ligand determines the monomeric (16b-18b, R3, R4 = Ph) or dimeric (11b-15b, R3 = R4 = H) structure of the complexes. The discussion of the stereochemical consequences caused by dimerization and chirality of the ligands is performed. The molecular structures of dimeric 11b, 12b, 15b, and monomeric 17b were studied by single-crystal X-ray diffraction. Complexes 11b, 12b, 14b, and 17b are active initiators in ring-opening polymerization of l-lactide in the absence of alcohol. Furthermore, 11b-13b, 17b, and 18b demonstrate an outstanding catalytic activity and selectivity in alcoholysis of l-lactide to give (S,S)-methyl lactyllactate.
- Zaitsev, Kirill V.,Cherepakhin, Valeriy S.,Zherebker, Alexander,Kononikhin, Alexey,Nikolaev, Eugene,Churakov, Andrei V.
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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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- Chiral Bis(oxazolidine)pyridine-copper-catalyzed enantioselective friedel-crafts alkylation of indoles with nitroalkenes
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Catalytic asymmetric Friedel-Crafts reaction of indoles with nitroalkenes was catalyzed by the stereochemically tunable bis(oxazolidine)pyridine (PyBodine)-Cu(OTf)2 complex. Using the PyBodine(Val)-Cu(OTf) 2 catalyst gave the Friedel-Crafts ?adducts with highly enantioselective manner. For the 1,4-bis[(E)-2-nitrovinyl]benzene, the reaction proceeded in a meso-trick manner to give the chiral double Friedel-Crafts adduct with 97% enantiomeric excess. Georg Thieme Verlag Stuttgart New York.
- Sato, Toru,Arai, Takayoshi
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p. 349 - 354
(2014/03/21)
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- Design, synthesis, and applications of potential substitutes of t-Bu-phosphinooxazoline in Pd-catalyzed asymmetric transformations and their use for the improvement of the enantioselectivity in the Pd-catalyzed allylation reaction of fluorinated allyl enol carbonates
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The design, synthesis, and applications of potential substitutes of t-Bu-PHOX in asymmetric catalysis is reported. The design relies on the incorporation of geminal substituents at C5 in combination with a substituent at C4 other than t-butyl (i-Pr, i-Bu, or s-Bu). Most of these new members of the PHOX ligand family behave similarly in terms of stereoinduction to t-Bu-PHOX in three palladium-catalyzed asymmetric transformations. Electronically modified ligands were also prepared and used to improve the enantioselectivity in the Pd-catalyzed allylation reaction of fluorinated allyl enol carbonates.
- Belanger, Etienne,Pouliot, Marie-France,Courtemanche, Marc-Andre,Paquin, Jean-Francois
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scheme or table
p. 317 - 331
(2012/02/15)
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- Large-scale synthesis of Singh's catalyst in a one-pot procedure starting from proline
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A practical one-pot procedure for the preparation of Singh's catalyst from either l-/d-proline or Boc-proline is described. The coupling partner, a chiral amino alcohol, can be prepared and used directly without purification from the corresponding amino acid ester. Moreover, a procedure for tert-butoxycarbonyl (Boc) group removal using concentrated HCl in MeOH-DCM was developed and utilized for the multigram-scale synthesis of Singh's catalyst.
- Berkessel, Albrecht,Harnying, Wacharee,Duangdee, Nongnaphat,Neudoerfl, Joerg-M.,Groeger, Harald
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experimental part
p. 123 - 128
(2012/05/20)
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- Direct asymmetric N-specific reaction of nitrosobenzene with aldehydes catalyzed by a chiral primary amine-based organocatalyst
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Nitroso compounds have two reactive nitrogen and oxygen atoms. It is interesting and important to perform a nitrogen or oxygen selective reaction with interesting substrates. These atom specific reactions are crucial to specifically synthesis of specific compounds. An enantioselective N-specific reaction of nitrosobenzene with unmodified aldehydes was successfully achieved catalyzed first by a variety of primary amine-based organocatalysts with higher yield and enantioselectivity. The bulkier substituted groups of the organocatalyst and two hydrogen bonds from the organocatalyst and the oxygen atom of nitrosobenzene make the reaction preferentially N-specific and predominantly afford R products.
- Qin, Long,Li, Lei,Yi, Lei,Da, Chao-Shan,Zhou, Yi-Feng
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experimental part
p. 527 - 533
(2012/01/11)
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- 2,4-Dinitrophenol as an effective cocatalyst: Greatly improving the activities and enantioselectivities of primary amine organocatalysts for asymmetric aldol reactions
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Seven primary amine organocatalysts 1a-g were readily prepared from natural primary amino acids via two steps and then were used to catalyze the direct asymmetric aldol reaction, but they showed very poor enantioselectivities and activities. As an effective cocatalyst, 2,4-dinitrophenol (DNP) dramatically elevated the activities and enantioselectivities of these very inefficient primary amine organocatalysts. This remedial course to the very inefficient organocatalysts by selection and employment of the optimal cocatalyst was particularly cost-effective and environment-beneficial compared with de novo development of catalysts. The highest efficient organocatalytic system that was composed of If and DNP showed high enantioselectivities and good to high diastereoselectivities with a broad spectrum of seven ketones. The linear ketones and cyclopentanone got predominant syn products whereas cyclohexanone mainly gave anti products.
- Da, Chao-Shan,Che, Li-Ping,Guo, Qi-Peng,Wu, Feng-Chun,Xiao, Ma.,Jia, Ya-Ning
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experimental part
p. 2541 - 2546
(2009/08/07)
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- Highly efficient primary amine organocatalysts for the direct asymmetric aldol reaction in brine
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Organocatalytic systems made up of six primary amine organocatalysts, derived from natural primary amino acids, in combination with 2,4-dinitrophenol (DNP) have proven to be efficient in the presence of brine without further addition of organic solvents. The system formed by 1f and DNP was the most efficient one; it can catalyze the direct aldol reaction with a broad range of ketones and aromatic aldehydes, giving the corresponding aldol products in high yields with up to nearly perfect diastereo- and enantioselectivities (up to 99/1 syn/anti, >99% ee).
- Ma, Xiao,Da, Chao-Shan,Yi, Lei,Jia, Ya-Ning,Guo, Qi-Peng,Che, Li-Ping,Wu, Feng-Chun,Wang, Jun-Rui,Li, Wei-Ping
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experimental part
p. 1419 - 1424
(2009/12/04)
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- Enantioselective addition of thiophenylboronic acids to aldehydes using ZnEt2/Schiff-base catalytic system
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Using Schiff-base amino alcohols as catalysts which were readily derived from natural amino acids in three steps, a series of valuable optically active thiophenyl methanols (4a-4n) were first obtained in good yields and high enantioselectivities (up to 96% ee) through the asymmetric addition of thiophenylboronic acid to aldehydes in the presence of ZnEt2 in toluene. Crown Copyright
- Liu, Xiaodong,Qiu, Li,Hong, Liang,Yan, Wenjing,Wang, Rui
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experimental part
p. 616 - 620
(2009/08/15)
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- Asymmetric reduction of prochiral ketones with N-sulfonylated amino alcohols as catalysts
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Novel N-sulfonylated amino alcohols were synthesized from L-amino acids and (+)-camphor, and their application to asymmetric reduction of prochiral ketones with NaBH4-BF3·Et2O is described. Copyright Taylor & Francis Group, LLC.
- Zhou, Zhongqiang,Guo, Yajing
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p. 684 - 696
(2008/09/16)
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- Enantioselective alkynylation of aromatic aldehydes catalyzed by new chiral oxazolidine ligands
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New chiral oxazolidines were conveniently synthesized from natural amino acids in three simple steps with good yields. The use of chiral oxazolidine ligands for the enantioselective alkynylation of aldehydes provides a simple, practical and inexpensive me
- Kang, Yong-Feng,Wang, Rui,Liu, Lei,Da, Chao-Shan,Yan, Wen-Jin,Xu, Zhao-Qing
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p. 863 - 865
(2007/10/03)
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- The use of bifunctional catalyst systems in the asymmetric addition of alkynylzinc to aldehydes
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The bifunctional ligand 2a showed a more enhanced reactivity than that of the corresponding amino alcohol ligand in the asymmetric addition of alkynylzinc to benzaldehyde. The bifunctional ligand 2a can catalyze the addition of phenylacetylene to various
- Kang, Yong-Feng,Liu, Lei,Wang, Rui,Yan, Wen-Jin,Zhou, Yi-Feng
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p. 3155 - 3159
(2007/10/03)
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- New chiral ligands derived from (S)-leucine for the enantioselective addition of diethylzinc to aldehydes
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A new series of chiral β-amino alcohols derived from (S)-leucine has been synthesized. The amino alcohol possessing a piperidine ring and a phenethyl group on the carbinol carbon atom was found to be an efficient ligand to catalyze the enantioselective addition of diethylzinc to aromatic (up to 97% ee) and aliphatic (up to 95% ee) aldehydes.
- Kawanami, Yasuhiro,Mitsuie, Tomoko,Miki, Misuzu,Sakamoto, Takanobu,Nishitani, Kazumi
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p. 175 - 178
(2007/10/03)
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- Synthesis of N-α-pyridylmethyl amino alcohols and application in catalytic asymmetric addition of diethylzinc to aromatic aldehydes
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A series of novel chiral ligands 2a-2f were conveniently prepared from β-amino alcohols through a two-step reaction and applied to catalyze the enantioselective addition of diethylzinc to benzaldehyde. Among them, ligand 2c was found to show the best asym
- Wu, Yangjie,Yun, Hongying,Wu, Yusheng,Ding, Kuiling,Zhou, Ying
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p. 3543 - 3552
(2007/10/03)
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- Asymmetric Synthesis Using Chirally Modified Borohydrides. Part 3. Enantioselective Reduction of Ketones and Oxime Ethers with Reagents Prepared from Borane and Chiral Amino Alcohols
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The asymmetric reduction of aromatic and aliphatic ketones, halogeno ketones, keto esters, and ketone oxime ethers with reagents prepared from borane and chiral amino alcohols has been investigated.When α,α-diphenyl-β-amino alcohols, such as (2S,3R)-(-)-2-amino-3-methyl-1,1-diphenylpentanol (2d), were used as a chiral auxiliary, very high enantioselectivities (ca. 90percent e.e.) were obtained in the reduction of various ketones and oxime ethers.
- Itsuno, Shinichi,Nakano, Michio,Miyazaki, Koji,Masuda, Hirofumi,Ito, Koichi,et al.
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p. 2039 - 2044
(2007/10/02)
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