- Simple primary β-amino alcohols as organocatalysts for the asymmetric Michael addition of β-keto esters to nitroalkenes
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Simple primary β-amino alcohols act as an efficient organocatalysts in the asymmetric Michael addition of β-keto esters with nitroalkenes affording highly pure chiral Michael adducts. Also, both enantiomers of the adducts were obtained, depending on the specific catalyst used and reaction temperature.
- Begum, Zubeda,Sannabe, Haruka,Seki, Chigusa,Okuyama, Yuko,Kwon, Eunsang,Uwai, Koji,Tokiwa, Michio,Tokiwa, Suguru,Takeshita, Mitsuhiro,Nakano, Hiroto
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p. 203 - 209
(2021/02/09)
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- Hybrid-Type Squaramide-Fused Amino Alcohol Organocatalysts for Enantioselective Nitro-Aldol Reaction of Nitromethane with Isatins
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A series of hybrid-type squaramide-fused amino alcohol (SFAA) catalysts were synthesized, and their catalytic efficiency in the enantioselective nitro-aldol reaction of various isatins with nitromethane has been described. This transformation afforded chiral 3-substituted 3-hydroxyoxindoles in excellent chemical yields (up to 99 %) with high enantioselectivities (up to 95 % ee). The resulting chiral 3-hydroxyoxindoles can be further used as synthetic precursors for the synthesis of several natural products that have a broad spectrum of fascinating biological activities.
- Chennapuram, Madhu,Subba Reddy,Seki, Chigusa,Okuyama, Yuko,Kwon, Eunsang,Uwai, Koji,Tokiwa, Michio,Takeshita, Mitsuhiro,Nakano, Hiroto
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p. 1638 - 1646
(2017/04/06)
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- Synthesis and applications in Henry reactions of novel chiral thiazoline tridentate ligands
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Several novel chiral tridentate ligands containing thiazoline were efficiently synthesized from commercially available l=cysteine in high yield. These ligands were subsequently applied to the asymmetric Henry reaction of nitromethane and various aldehydes. It was found that the structures of the thiazoline ligands had a significant influence on the enantioselectivity. It was shown that the optimal catalyst for this reaction was a ligand complexed with CuCl, which was formed from chiral thiazoline with chiral aminoalcohol. At -20°C, with 10 mol% of this ligand, a product with (S)-configuration was isolated in 93% yield and 98% enantiomeric excess.
- Shi, Ye,Li, Yang,Sun, Jingbo,Lai, Qi,Wei, Chiyu,Gong, Zhiyong,Gu, Qiang,Song, Zhiguang
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p. 661 - 667
(2015/09/28)
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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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- COMPOSITIONS AND METHODS FOR CYCLOFRUCTANS AS SEPARATION AGENTS
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The present invention relates to derivatized cyclofructan compounds, compositions comprising derivatized cyclofructan compounds, and methods of using compositions comprising derivatized cyclofructan compounds for chromatographic separations of chemical species, including enantiomers. Said compositions may comprise a solid support and/or polymers comprising derivatized cyclofructan compounds.
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Page/Page column 45-49; 64
(2010/12/31)
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- Kinetic investigation of the reduction of pinacolone by borane catalyzed by oxazaborolidines in THF. Hydride shift as rate determining step
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The kinetics of the reduction of the ketone pinacolone (P) by borane (B) catalyzed by the oxazaborolidines (OAB) (S)-1-methyl-3,3-diphenylperhydropyrrolo[1,2-c][1,3,2]oxazaborolidine and (S)-2,4-dimethyl-3,3-diphenyl-1,3,2-oxazaborolidine have been studied in THF. The findings are discussed in comparison with the kinetic results obtained previously for the same reaction using two different OABs as catalysts (C). The reaction order in the ketone P changes in the series of OABs from first-order to zero-order. This surprising behaviour excludes the addition of P to the binary complex C-B forming the ternary complex P-C-B as the rate determining step. However, the kinetic data are consistently explained if the intramolecular hydride shift in P-C-B with subsequent rearrangement leading to the complex of monoalkoxyborane and catalyst is assumed to be rate determining. The rate equations of the catalytic reactions of the four OABs, the corresponding ee values, and apparent activation energies are given.
- Jockel, Holger,Schmidt, Reinhard,Jope, Helge,Schmalz, Hans-Guenther
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- Binuclear versus mononuclear copper complexes as catalysts for asymmetric cyclopropanation of styrene
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A number of (S)-(-)-2-amino-1,1-diaryl-1-propanol compounds have been synthesized. They were used to form the binuclear copper complexes through a spontaneous assembly of the individual components, the β-aminoalcohol, 2- hydroxy-5-methyl-1,3-benzenedialdehyde, and copper acetate monohydrate, in methanol. These binuclear complexes were examined as asymmetric catalysts for cyclopropanation of styrene by ethyl diazoacetate. Moderate improvement in enantioselectivity has been observed for the binuclear versus mononuclear copper complexes. The e.e. values up to 87% for trans and 93% for cis products and the ratio between trans and cis products up to 9:1 have been obtained.
- Cai, Lisheng,Mahmoud, Hussein,Han, Ying
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p. 411 - 427
(2007/10/03)
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- DICARBOXIMIDE-BASED CLATHRATE DESIGN. HOST SYNTHESIS, INCLUSION FORMATION AND X-RAY CRYSTAL STRUCTURES OF A FREE HOST AND OF INCLUSION COMPOUDS WITH 2- AND 3-METHYLCYCLOHEXANONE, 3-METHYLCYCLOPENTANONE, BUTYRONITRILE, PROPAN-1-OL and (-)-FENCHONE GUESTS
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Crystalline host compounds consisting of a roof-shaped dicarboximide framework and pendant diarylethanol analogous subunits were synthesized and shown to form inclusion complexes with small organic molecules such as alcohols, amines, ketones or polar and apolar organic solvents.Clathrate efficiency and selectivity depend on the particular host structure.The crystal and molecular structures of a free host compound (2a) and inclusion compounds were determined by x-ray diffraction analysis.In all the structures, the hydroxyl group is involved in intramolecular hydrogen bonds and the host and guest molecules are held by lattice forces only.The channels and cavities left in the host matrix are large enough to allow disorder or high thermal displacement parameters of the guest molecules.The local packing coeffecients for all guests are 0.42 on average.
- Weber, Edwin,Reutel, Christiane,Foces-Foces, Concepcion,Llamas-Saiz, Antonio L.
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p. 159 - 170
(2007/10/02)
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- Asymmetric Ketone Reduction using Chiral Oxazaborolidines derived from Aziridine Carbinols
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Asymmetric borane reduction of acetophenone using 1,3,2-oxazaborolidines derived from aziridine-2-tertiary alcohols 1 and 2 yielded the corresponding alcohol in high optical yields.The synthesis of the novel chiral catalysts 1 and 2 using D-and L-serine,
- Willems, Johannes G. H.,Dommerholt, F. Jan,Hammink, Jeannet B.,Vaarhorst, Ariaela M.,Thijs, Lambertus,Zwanenburg, Binne
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p. 603 - 606
(2007/10/02)
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- Alanine-derived Hosts Comprising a Roof-shaped Carbonimide Framework. Synthesis, Inclusion Formation and X-Ray Crystal Structures of Racemic and Optically Resolved Free Hosts, and their Crystalline Complexes with 3-Methylcyclohexanone
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A chiral crystalline host molecule derived from the amino acid alanine comprising a characteristic 9,10-dihydro-9,10-ethanoanthracene-11,12-dicarboximide framework as an inclusion-promoting group has been synthesized in optically resolved and racemic forms and studied with regard to their inclusion behaviour.Dependent on the optical resolution state, this host forms crystalline inclusion compounds with a great variety of uncharged organic molecules ranging from protic dipolar to rather apolar compounds (78 different inclusion species) with the racemic host being more efficient.X-Ray crystal structures of the optically resolved and racemic uncomplexed host species and of their 1:1 inclusion complexes with 3-methylcyclohexanone are reported.The host hydroxy groups are always involved in O-H...O=C intramolecular hydrogen bonds.The crystal packings of both complexes are analogous, showing similar cell dimensions and space groups P21 and P21/a.Moreover, the two independent molecules in the resolved complex are almost related by a pseudo centre of symmetry.
- Weber, Edwin,Reutel, Christiane,Foces-Foces, Concepcion,Llamas-Saiz, Antonio L.
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p. 1455 - 1462
(2007/10/02)
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- Synthesis of Optically Active Siloxycyclopropanes by Asymmetric Catalysis, I. - Influence of the Catalyst on the Cyclopropanation of (Z)-1-Phenyl-1-(trimethylsiloxy)prop-1-ene
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The cyclopropanation of silyl enol ether 1a with methyl diazoacetate (2a) and diazoesters 2b-d in the presence of optically active copper salicylimine complexes 4-Cu was systematically studied.Up to 88percent enantiomeric excess in products 3 were obtained by employing the appropriate reaction conditions and the optimal catalyst ligands.Thus, for the first time respectable optical yields were achieved in asymmetric cyclopropanations of silyl enol ethers with easily available copper-Schiff base catalysts.The ring opening of the separated diastereomers of 3a employing nBu4NF provided methyl γ-oxocarboxylate 6a in good optical purity.This demonstrates that this process occurs without racemization and also that 3a is formed with the same absolute configuration at C-1. - Key Words: Cyclopropanecarboxylates, 2-silyloxy, methyl / Cycloaddition / Enantioselectivity / Asymmetric catalysis / Copper-Schiff base complexes, chiral
- Dammast, Franziska,Reissig, Hans-Ulrich
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p. 2449 - 2456
(2007/10/02)
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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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