- Stereoselective protonation of 2-methyl-1-tetralone lithium enolate catalyzed by salan-type diamines
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Asymmetric protonation of ketone enolates is a convenient alternative to asymmetric alkylation of enolates that allows to convert racemic ketones into their optically active form. Here, we have reported an efficient enantioselective protonation of 2-methyl-1-tetralone lithium enolate catalyzed by salan-type diamines. A broad series of salan-type catalysts were synthesized, including several previously unknown, and subsequently tested in the title reaction. For the first time, a chiral amine used as organocatalyst has shown better results than as stoichiometric protonating agent. Application of only 10 mol% of salan allows to obtain the title ketone with high yield and enantiomeric excess up to 75%. The DFT calculations of the structure of the catalyst and its complex with lithium enolate were conducted, which makes it possible to propose a likely reaction mechanism.
- ?owicki, Daniel,Watral, Justyna,Jelecki, Maciej,Bohusz, Wiktor,Kwit, Marcin
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- Organocatalytic Asymmetric Tandem α-Aminooxylation–Henry Reactions for the Synthesis of 1,2-Diols: Total Synthesis of (–)-l-threo-Sphinganine
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A new and rapid asymmetric synthesis of anti- and syn-β,γ-dihydroxynitroalkanes through an organocatalytic tandem α-aminooxylation–Henry reaction is described. The target diol derivatives were synthesized in good yields, with excellent enantioselectivitie
- Garg, Yuvraj,Kaur, Ramandeep,Kumar Pandey, Satyendra
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p. 6700 - 6707
(2017/12/07)
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- PROCESS FOR THE PREPARATION OF ENANTIOMERICALLY ENRICHED PROTON PUMP INHIBITORS
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The invention discloses a process for the preparation of compounds having structures typical for proton pump inhibitors in enantiomerically enriched form by using particular metal catalysts in an enantioselective oxidation step. Also disclosed are useful further processes and pure intermediate and subsequently final products.
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Page/Page column 29
(2010/04/30)
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- Critical role of external axial ligands in chirality amplification of trans-cyclohexane-1,2-diamine in salen complexes
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A series of MnIV(salen)(L)2 complexes bearing different external axial ligands (L ) Cl, NO3, N3, and OCH2CF3) from chiral salen ligands with trans-cyclohexane-1,2-diamine as a chiral scaffo
- Kurahashi, Takuya,Hada, Masahiko,Fujii, Hiroshi
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experimental part
p. 12394 - 12405
(2010/01/30)
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- Titanium-salan-catalyzed asymmetric oxidation of sulfides and kinetic resolution of sulfoxides with H2O2 as the oxidant
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Asymmetric oxidation of sufides to sulfoxides by aqueous hydrogen peroxide with catalysis by titanium-salan complexes is presented. Optically active sulfoxides have been obtained with good to high enantioselectivities (up to 97% ee) by a tandem enantioselective oxidation and kinetic resolution procedure, the catalyst performing over 500 turnovers with no loss of enantioselectivity. Wiley-VCH Verlag GmbH & Co. KGaA, 2008.
- Bryliakov, Konstantin P.,Talsi, Evgenii P.
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experimental part
p. 3369 - 3376
(2009/04/07)
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- PROCESS FOR PRODUCING OPTICALLY ACTIVE EPOXY COMPOUND, COMPLEX FOR USE IN THE PROCESS, AND PROCESS FOR PRODUCING THE SAME
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There is provided a method for industrially producing optically active epoxy compounds by asymmetrically epoxidizing prochiral unsaturated compounds with an oxidant using as a catalyst a single substance or a di-μ-oxo dimer derived therefrom represented by any of the following formulae (I), (I'), (II), (II'), (III), (III'), (IV), and (IV'): [wherein R1s are independently an alkyl group or an aryl group; R2s are independently an alkyl group or an aryl group; R3s are independently an alkyl group or an aryl group, provided that two R3s may be bonded with each other to form a ring; R4s are independently a hydrogen atom, a halogen atom, an alkyl group, an alkoxy group, a nitro group, or a cyano group; M is TiY2 (Y is Cl, alkoxide, or a μ-oxo ligand)].
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Page/Page column 17-18
(2010/11/28)
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- Diastereomerically-specific zirconium complexes of chiral salan ligands: Isospecific polymerization of 1-hexene and 4-methyl-1-pentene and cyclopolymerization of 1,5-hexadiene
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Chiral Salan ligands were found to wrap in a highly diastereoselective manner around zirconium leading to C2-symmetric complexes of predetermined chirality at the metal. These complexes led to active polymerization of higher olefins, their activity and is
- Yeori, Adi,Goldberg, Israel,Shuster, Michael,Kol, Moshe
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p. 13062 - 13063
(2008/02/08)
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- Efficient asymmetric oxidation of sulfides and kinetic resolution of sulfoxides catalyzed by a vanadium-salan system
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The asymmetric oxidation of sulfides to chiral sulfoxides with hydrogen peroxide in good yield and high enantioselectivity has been catalyzed very effectively by chiral vanadium-salan [N,N′-alkyl bis(salicylamine)] complex. The salan ligand shows results superior in terms of reactivity and enantioselectivity to those of salen [N,N′-alkylene bis(salicylideneimine) ] analogue, and provides the sulfoxide with opposite configuration. The high enantioselectivity of this reaction is the direct result of the asymmetric oxidation. The efficient kinetic resolution of racemic sulfoxides catalyzed by the vanadium-salan system is also described.
- Sun, Jiangtao,Zhu, Chengjian,Dai, Zhenya,Yang, Minghua,Pan, Yi,Hu, Hongwen
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p. 8500 - 8503
(2007/10/03)
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- Single-step synthesis of salans and substituted salans by Mannich condensation
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A convenient route for the synthesis of a variety of salan-type compounds is introduced. The synthesis is based on a single-step Mannich condensation between readily available starting materials: primary or secondary amines, formaldehyde and substituted phenols. This methodology is suitable for the preparation of chiral salans as well, which may find applications in asymmetric catalysis.
- Tshuva, Edit Y,Gendeziuk, Natalie,Kol, Moshe
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p. 6405 - 6407
(2007/10/03)
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