96156-72-8Relevant academic research and scientific papers
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.
Amino Acid-Functionalized Metal-Organic Frameworks for Asymmetric Base–Metal Catalysis
Newar, Rajashree,Akhtar, Naved,Antil, Neha,Kumar, Ajay,Shukla, Sakshi,Begum, Wahida,Manna, Kuntal
supporting information, p. 10964 - 10970 (2021/03/29)
We report a strategy to develop heterogeneous single-site enantioselective catalysts based on naturally occurring amino acids and earth-abundant metals for eco-friendly asymmetric catalysis. The grafting of amino acids within the pores of a metal-organic framework (MOF), followed by post-synthetic metalation with iron precursor, affords highly active and enantioselective (>99 % ee for 10 examples) catalysts for hydrosilylation and hydroboration of carbonyl compounds. Impressively, the MOF-Fe catalyst displayed high turnover numbers of up to 10 000 and was recycled and reused more than 15 times without diminishing the enantioselectivity. MOF-Fe displayed much higher activity and enantioselectivity than its homogeneous control catalyst, likely due to the formation of robust single-site catalyst in the MOF through site-isolation.
Chiral Iron(II)-Catalysts within Valinol-Grafted Metal-Organic Frameworks for Enantioselective Reduction of Ketones
Akhtar, Naved,Antil, Neha,Begum, Wahida,Chauhan, Manav,Kumar, Ajay,Manna, Kuntal,Newar, Rajashree
, p. 10450 - 10459 (2021/08/31)
The development of highly efficient and enantioselective heterogeneous catalysts based on earth-abundant elements and inexpensive chiral ligands is essential for environment-friendly and economical production of optically active compounds. We report a strategy of synthesizing chiral amino alcohol-functionalized metal-organic frameworks (MOFs) to afford highly enantioselective single-site base-metal catalysts for asymmetric organic transformations. The chiral MOFs (vol-UiO) were prepared by grafting of chiral amino alcohol such as l-valinol within the pores of aldehyde-functionalized UiO-MOFs via formation of imine linkages. The metalation of vol-UiO with FeCl2 in THF gives amino alcohol coordinated octahedral FeII species of vol-FeCl(THF)3 within the MOFs as determined by X-ray absorption spectroscopy. Upon activation with LiCH2SiMe3, vol-UiO-Fe catalyzed hydrosilylation and hydroboration of a range of aliphatic and aromatic carbonyls to afford the corresponding chiral alcohols with enantiomeric excesses up to 99%. Vol-UiO-Fe catalysts have high turnover numbers of up to 15 ?000 and could be reused at least 10 times without any loss of activity and enantioselectivity. The spectroscopic, kinetic, and computational studies suggest iron-hydride as the catalytic species, which undergoes enantioselective 1,2-insertion of carbonyl to give an iron-alkoxide intermediate. The subsequent σ-bond metathesis between Fe-O bond and Si-H bond of silane produces chiral silyl ether. This work highlights the importance of MOFs as the tunable molecular material for designing chiral solid catalysts based on inexpensive natural feedstocks such as chiral amino acids and base-metals for asymmetric organic transformations.
Arene-Immobilized Ru(II)/TsDPEN Complexes: Synthesis and Applications to the Asymmetric Transfer Hydrogenation of Ketones
Doherty, Simon,Knight, Julian G.,Alshaikh, Hind,Wilson, James,Waddell, Paul G.,Wills, Corinne,Dixon, Casey M.
supporting information, p. 226 - 235 (2020/12/31)
The Noyori-Ikariya (arene)Ru(II)/TsDPEN precatalyst has been anchored to amorphous silica and DAVISIL through the η6-coordinated arene ligand via a straightforward synthesis and the derived systems, (arene)Ru(II)/TsDPEN@silica and (arene)Ru(II)/TsDPEN@DAVISIL, form highly efficient catalysts for the asymmetric transfer hydrogenation of a range of electron-rich and electron-poor aromatic ketones, giving good conversion and excellent ee's under mild reaction conditions. Moreover, catalyst generated in situ immediately prior to addition of substrate and hydrogen donor, by reaction of silica-supported [(arene)RuCl2]2 with (S,S)-TsDPEN, was as efficient as that generated from its preformed counterpart [(arene)Ru{(S,S)-TsDPEN}Cl]@silica. Gratifyingly, the initial TOFs (up to 1085 h?1) and ee's (96–97 %) obtained with these catalysts either rivalled or outperformed those previously reported for catalysts supported by either silica or polymer immobilized through one of the nitrogen atoms of TsDPEN. While the high ee's were also maintained during recycle studies, the conversion dropped steadily over the first three runs due to gradual leaching of the ruthenium.
C1-Symmetric PNP Ligands for Manganese-Catalyzed Enantioselective Hydrogenation of Ketones: Reaction Scope and Enantioinduction Model
Zeng, Liyao,Yang, Huaxin,Zhao, Menglong,Wen, Jialin,Tucker, James H. R.,Zhang, Xumu
, p. 13794 - 13799 (2020/11/30)
A family of ferrocene-based chiral PNP ligands is reported. These tridentate ligands were successfully applied in Mn-catalyzed asymmetric hydrogenation of ketones, giving high enantioselectivities (92%～99% ee for aryl alkyl ketones) as well as high efficiencies (TON up to 2000). In addition, dialkyl ketones could also be hydrogenated smoothly. Manganese intermediates that might be involved in the catalytic cycle were analyzed. DFT calculation was carried out to help understand the chiral induction model. The Mn/PNP catalyst could discriminate two groups with different steric properties by deformation of the phosphine moiety in the flexible 5-membered ring.
Efficient asymmetric synthesis of chiral alcohols using high 2-propanol tolerance alcohol dehydrogenase: Sm ADH2 via an environmentally friendly TBCR system
Yang, Zeyu,Fu, Hengwei,Ye, Wenjie,Xie, Youyu,Liu, Qinghai,Wang, Hualei,Wei, Dongzhi
, p. 70 - 78 (2020/01/21)
Alcohol dehydrogenases (ADHs) together with the economical substrate-coupled cofactor regeneration system play a pivotal role in the asymmetric synthesis of chiral alcohols; however, severe challenges concerning the poor tolerance of enzymes to 2-propanol and the adverse effects of the by-product, acetone, limit its applications, causing this strategy to lapse. Herein, a novel ADH gene smadh2 was identified from Stenotrophomonas maltophilia by traditional genome mining technology. The gene was cloned into Escherichia coli cells and then expressed to yield SmADH2. SmADH2 has a broad substrate spectrum and exhibits excellent tolerance and superb activity to 2-propanol even at 10.5 M (80%, v/v) concentration. Moreover, a new thermostatic bubble column reactor (TBCR) system is successfully designed to alleviate the inhibition of the by-product acetone by gas flow and continuously supplement 2-propanol. The organic waste can be simultaneously recovered for the purpose of green synthesis. In the sustainable system, structurally diverse chiral alcohols are synthesised at a high substrate loading (>150 g L-1) without adding external coenzymes. Among these, about 780 g L-1 (6 M) ethyl acetoacetate is completely converted into ethyl (R)-3-hydroxybutyrate in only 2.5 h with 99.9% ee and 7488 g L-1 d-1 space-time yield. Molecular dynamics simulation results shed light on the high catalytic activity toward the substrate. Therefore, the high 2-propanol tolerance SmADH2 with the TBCR system proves to be a potent biocatalytic strategy for the synthesis of chiral alcohols on an industrial scale.
Redox-driven deracemization of secondary alcohols by sequential ether/O2-mediated oxidation and Ru-catalyzed asymmetric reduction
Yang, Bing,Cui, Peng,Chen, Yongsheng,Liu, Qixing,Zhou, Haifeng
, (2020/10/14)
The deracemization of benzylic alcohols has been achieved using a redox-driven one-pot two-step process. The racemic alcohols were oxidized by bis(methoxypropyl) ether and oxygen to give the ketone intermediates, followed by an asymmetric transfer hydrogenation with a chiral ruthenium catalyst. This compatible oxidation/reduction process gave the enantiomerically enriched alcohols with up to 95% ee values.
Imine containing C2-Symmetric chiral half sandwich η6-p-cymene-Ru(II)- phosphinite complexes: Investigation of their catalytic activity in the asymmetric transfer hydrogenation of ketones
Saleh, Najmuldain Abdullah,Pa?a, Salih,Kayan, Cezmi,Meri?, Nermin,Sünkür, Murat,Aral, Tar?k,Aydemir, Murat,Baysal, Ak?n,Durap, Feyyaz
, (2019/10/08)
New chiral C2-symmetric bis(phosphinite) ligands containing imine group were synthesized from 1-({[(1R,2R)-2-{[(2-hydroxynaphthalen-1-yl)methylidene] amino}cyclohexyl]- imino}methyl)- naphthalen-2-ol and two equivalents of Ph2PCl, (i-Pr)2PCl or (Cy)2PCl, in high yields. Binuclear C2-symmetric half sandwich η6-p-cymene-Ru(II) complexes of the chiral phosphinite ligands were synthesized by treating of [Ru(η6-p-cymene)(μ-Cl)Cl]2 with the phosphinites in 1:1 M ratio in CH2Cl2. Their catalytic activities in asymmetric transfer hydrogenation (ATH) were investigated for the reaction of acetophenone derivatives with isopropyl alcohol. The corresponding optically active secondary alcohols were obtained in excellent levels of conversion (96–99%) and moderate enantioselectivity (up to 60% ee). Among three complexes investigated, complex 4 was the most efficient one.
SECONDARY ARYL ALCOHOL AND METHOD OF SYNTHESIZING THEREOF
-
Paragraph 0032; 0062-0069, (2020/05/13)
The present invention relates to secondary aryl alcohol and a method for synthesizing the same and, specifically, to synthesizing secondary aryl alcohol having high optical selectivity through a hydrosilylation reaction using ketone containing an aryl group. In the method for synthesizing secondary aryl alcohol according to an embodiment of the present invention, secondary aryl alcohol is synthesized by making ketone react with hydrosilane under a chiral boron Lewis acid catalyst.COPYRIGHT KIPO 2020
One-pot Chemoenzymatic Deracemisation of Secondary Alcohols Employing Variants of Galactose Oxidase and Transfer Hydrogenation
Yuan, Bo,Debecker, Damien P.,Wu, Xiaofeng,Xiao, Jianliang,Fei, Qiang,Turner, Nicholas J.
, p. 6191 - 6195 (2020/10/15)
Enantiomerically enriched chiral secondary alcohols serve as valuable building blocks for drug intermediates and fine chemicals. In this study the deracemisation of secondary alcohols to generate enantiomeric pure chiral alcohols has been achieved by combining enantio-selective enzymatic oxidation of a secondary alcohol, by a variant of GOase (GOase M3-5), with either non-selective ketone reduction via transfer hydrogenation (TH) or enantio-selective asymmetric transfer hydrogenation (ATH). Both the enzymatic oxidation system and the transition-metal mediated reduction system were optimised to ensure compatibility with each other resulting in a homogeneous reaction system. 1-(4-nitrophenyl)ethanol was generated with 99 % conversion and 98 % ee by the deracemisation method, and it has been extended to a series of other secondary alcohols with comparable results.
