27544-18-9Relevant articles and documents
Asymmetric reduction of ketones with sodium aluminum hydride modified by various chiral diols
Vinogradov,Gorshkova,Pavlov,Mikhalev,Chel'tsova,Razmanov,Ferapontov,Malyshev,Heise
, p. 460 - 465 (2000)
New stereoselective reducing reagents were prepared in situ by modification of NaAlH4 with various chiral diols. The efficiency of 1,4- and 1,3-diols as chiral auxiliaries in the reactions of alkyl aryl ketones with modified NaAlH4 was considerably higher than that of 1,2-diols. The effect of the nature of the achiral ligand additionally introduced into the chiral hydride reagent on the enantioselectivity of ketone reduction was studied. It was proposed that the sodium cation does not necessarily participate at the stage governing the reaction stereochemistry.
Periodic mesoporous organosilicas with trans-(1R,2R)-diaminocyclohexane in the framework: A potential catalytic material for asymmetric reactions
Jiang, Dongmei,Yang, Qihua,Wang, Hong,Zhu, Guiru,Yang, Jie,Li, Can
, p. 65 - 73 (2006)
With benzyl group as a linker, trans-(1R,2R)-diaminocyclohexane was incorporated into the framework of mesoporous silica through one-step co-condensation of tetramethoxysilane with N,N′-bis[4-(trimethoxysilyl) benzyl]-(-)-(1R,2R)-diaminocyclohexane using cetyltrimethylammonium bromide as a structure-directing agent under basic conditions. All materials were fully characterized by X-ray diffraction, N2 sorption isotherms, transmission electron microscopy, and 13C and 29Si cross-polarization magic-angle spinning nuclear magnetic resonance spectroscopy. Coordinated with [Rh(cod)Cl]2, the material exhibited a TOF up to ～414 h-1 with 30% ee for the asymmetric transfer hydrogenation of acetophenone. Various ketones were hydrogenated with different activities and enantioselectivities. An enantioselectivity of about 61% ee was observed in the case of 2-acetylnaphthalene. Moreover, a comparison of the catalytic properties of the materials with benzyl and propyl groups as linkers indicates the importance of the rigidity and electron-withdrawing ability of the linker in the high reaction rate of the catalysts.
The Size-Accelerated Kinetic Resolution of Secondary Alcohols
P?lloth, Benjamin,Sibi, Mukund P.,Zipse, Hendrik
, p. 774 - 778 (2021)
The factors responsible for the kinetic resolution of alcohols by chiral pyridine derivatives have been elucidated by measurements of relative rates for a set of substrates with systematically growing aromatic side chains using accurate competitive linear regression analysis. Increasing the side chain size from phenyl to pyrenyl results in a rate acceleration of more than 40 for the major enantiomer. Based on this observation a new catalyst with increased steric bulk has been designed that gives enantioselectivity values of up to s=250. Extensive conformational analysis of the relevant transition states indicates that alcohol attack to the more crowded side of the acyl-catalyst intermediate is favoured due to stabilizing CH-π-stacking interactions. Experimental and theoretical results imply that enantioselectivity enhancements result from accelerating the transformation of the major enantiomer through attractive non-covalent interactions (NCIs) rather than retarding the transformation of the minor isomer through repulsive steric forces.
Studies on the Regio- and Enantioselectivity of the Lipase-catalyzed Transestriffication of 1'- and 2'-Naphthyl Alcohols in Organic Solvent
Ferraboschi, Patrizia,Casati, Silvana,Manzocchi, Ada,Santaniello, Enzo
, p. 1521 - 1524 (1995)
The Pseudomonas cepacia lipase preferentially acylates the 2'-regioisomers of a few 1'- and 2'-naphthyl alcohols; in the case of compounds 3a, 3c, 4a, 4c the (R)-alcohols (65- >98percent ee) and the (S)-acetates (62-98percent ee) are formed.
Asymmetric reductions in aqueous media: Enzymatic synthesis in cyclodextrin containing buffers
Zelinski, Thomas,Liese, Andreas,Wandrey, Christian,Kula, Maria-Regina
, p. 1681 - 1687 (1999)
The enzymatic reduction of hydrophobic ketones in cyclodextrin containing media is reported yielding the corresponding alcohols (S)-1-(2- naphthyl)-ethanol, (S)-(E)-4-phenyl-3-en-2-ol and 1,2,3,4-tetrahydro-2- (1hydroxyethyl)-1-oxonaphthalene in good yiel
Cinchona-Alkaloid-Derived NNP Ligand for Iridium-Catalyzed Asymmetric Hydrogenation of Ketones
Zhang, Lin,Zhang, Ling,Chen, Qian,Li, Linlin,Jiang, Jian,Sun, Hao,Zhao, Chong,Yang, Yuanyong,Li, Chun
supporting information, p. 415 - 419 (2022/01/12)
Most ligands applied for asymmetric hydrogenation are synthesized via multistep reactions with expensive chemical reagents. Herein, a series of novel and easily accessed cinchona-alkaloid-based NNP ligands have been developed in two steps. By combining [Ir(COD)Cl]2, 39 ketones including aromatic, heteroaryl, and alkyl ketones have been hydrogenated, all affording valuable chiral alcohols with 96.0-99.9% ee. A plausible reaction mechanism was discussed by NMR, HRMS, and DFT, and an activating model involving trihydride was verified.
Visible-Light-Driven Catalytic Deracemization of Secondary Alcohols
Zhang, Zhikun,Hu, Xile
supporting information, p. 22833 - 22838 (2021/09/09)
Deracemization of racemic chiral compounds is an attractive approach in asymmetric synthesis, but its development has been hindered by energetic and kinetic challenges. Here we describe a catalytic deracemization method for secondary benzylic alcohols which are important synthetic intermediates and end products for many industries. Driven by visible light only, this method is based on sequential photochemical dehydrogenation followed by enantioselective thermal hydrogenation. The combination of a heterogeneous dehydrogenation photocatalyst and a chiral molecular hydrogenation catalyst is essential to ensure two distinct pathways for the forward and reverse reactions. These reactions convert a large number of racemic aryl alkyl alcohols into their enantiomerically enriched forms in good yields and enantioselectivities.
Phase Separation-Promoted Redox Deracemization of Secondary Alcohols over a Supported Dual Catalysts System
Zhao, Zhitong,Wang, Chengyi,Chen, Qipeng,Wang, Yu,Xiao, Rui,Tan, Chunxia,Liu, Guohua
, p. 4055 - 4063 (2021/08/12)
Unification of oxidation and reduction in a one-pot deracemization process has great significance in the preparation of enantioenriched organic molecules. However, the intrinsic mutual deactivation of oxidative and reductive catalysts and the extrinsic incompatible reaction conditions are unavoidable challenges in a single operation. To address these two issues, we develop a supported dual catalysts system to overcome these conflicts from incompatibility to compatibility, resulting in an efficient one-pot redox deracemization of secondary alcohols. During this transformation, the TEMPO species onto the outer surface of silica nanoparticles catalyze the oxidation of racemic alcohols to ketones, and the chiral Rh/diamine species in the nanochannels of the thermoresponsive polymer-coated hollow-shell mesoporous silica enable the asymmetric transfer hydrogenation (ATH) of ketones to chiral alcohols. To demonstrate the general feasibility, a series of orthogonal oxidation/ATH cascade reactions are compared to prove the compatible benefits in the elimination of their deactivations and the balance of the cascade directionality. As presented in this study, this redox deracemization process provides various chiral alcohols with enhanced yields and enantioselectivities relative to those from unsupported dual catalysts systems. Furthermore, the dual catalysts can be recycled continuously, making them an attractive feature in the application.
