4754-27-2Relevant articles and documents
Minisci-Type Alkylation of N-Heteroarenes by N-(Acyloxy)phthalimide Esters Mediated by a Hantzsch Ester and Blue LED Light
Kyne, Sara Helen,Li, Jiacheng,Siang Tan, Suan,Wai Hong Chan, Philip
supporting information, (2022/01/11)
A synthetic method that enables the Hantzsch ester-mediated Minisci-type C2-alkylation of quinolines, isoquinolines and pyridines by N-(acyloxy)phthalimide esters (NHPI) under blue LED (light emitting diode) light (456 nm) is described. Achieved under mild reaction conditions at room temperature, the metal-free synthetic protocol was shown to be applicable to primary, secondary and tertiary NHPIs to give the alkylated N-heterocyclic products in yields of 21–99%. On introducing a chiral phosphoric acid, an asymmetric version of the reaction was also realised and provided product enantiomeric excess (ee) values of 53–99%. The reaction mechanism was delineated to involve excitation of an electron-donor acceptor (EDA) complex, formed from weak electrostatic interactions between the Hantzsch ester and NHPI, which generates the posited radical species of the redox active ester that undergoes addition to the N-heterocycle.
Ruthenium-p-cymene Complex Side-Wall Covalently Bonded to Carbon Nanotubes as Efficient Hybrid Transfer Hydrogenation Catalyst
Blanco, Matías,Cembellín, Sara,Agnoli, Stefano,Alemán, José
, p. 5156 - 5165 (2021/11/05)
A half-sandwich ruthenium-p-cymene organometallic complex has been immobilized at Single Walled Carbon Nanotubes (SWNT) sidewalls through a stepwise covalent chemistry protocol. The introduction of amino groups by means of diazonium-chemistry protocols leads the grafting at the outer walls of the nanotubes. This hybrid material is active in the transfer hydrogenation of ketones to yield alcohols, using as hydrogen source 2-propanol. SWNT?NH2?Ru presents a broad scope, performing the reaction under aerobic conditions and can be recycled over 9 consecutive reaction runs without losing activity or leaching ruthenium out. Comparison of the activity with related homogeneous catalysts reveals an improved performance due to the covalent bond between the metal and the material, achieving turnover frequencies as high as 192774 h?1.
Manganese-catalyzed homogeneous hydrogenation of ketones and conjugate reduction of α,β-unsaturated carboxylic acid derivatives: A chemoselective, robust, and phosphine-free in situ-protocol
Topf, Christoph,Vielhaber, Thomas
, (2021/07/10)
We communicate a user-friendly and glove-box-free catalytic protocol for the manganese-catalyzed hydrogenation of ketones and conjugated C[dbnd]C[sbnd]bonds of esters and nitriles. The respective catalyst is readily assembled in situ from the privileged [Mn(CO)5Br] precursor and cheap 2-picolylamine. The catalytic transformations were performed in the presence of t-BuOK whereby the corresponding hydrogenation products were obtained in good to excellent yields. The described system offers a brisk and atom-efficient access to both secondary alcohols and saturated esters avoiding the use of oxygen-sensitive and expensive phosphine-based ligands.
Cobalt-catalyzed asymmetric hydrogenation of ketones: A remarkable additive effect on enantioselectivity
Du, Tian,Wang, Biwen,Wang, Chao,Xiao, Jianliang,Tang, Weijun
supporting information, p. 1241 - 1244 (2020/10/02)
A chiral cobalt pincer complex, when combined with an achiral electron-rich mono-phosphine ligand, catalyzes efficient asymmetric hydrogenation of a wide range of aryl ketones, affording chiral alcohols with high yields and moderate to excellent enantioselectivities (29 examples, up to 93% ee). Notably, the achiral mono-phosphine ligand shows a remarkable effect on the enantioselectivity of the reaction.
Manganese catalyzed asymmetric transfer hydrogenation of ketones
Zhang, Guang-Ya,Ruan, Sun-Hong,Li, Yan-Yun,Gao, Jing-Xing
supporting information, p. 1415 - 1418 (2020/11/20)
The asymmetric transfer hydrogenation (ATH) of a wide range of ketones catalyzed by manganese complex as well as chiral PxNy-type ligand under mild conditions was investigated. Using 2-propanol as hydrogen source, various ketones could be enantioselectively hydrogenated by combining cheap, readily available [MnBr(CO)5] with chiral, 22-membered macrocyclic ligand (R,R,R',R')-CyP2N4 (L5) with 2 mol% of catalyst loading, affording highly valuable chiral alcohols with up to 95% ee.
Ruthenium-catalyzed hydrogenation of aromatic ketones using chiral diamine and monodentate achiral phosphine ligands
Wang, Mengna,Zhang, Ling,Sun, Hao,Chen, Qian,Jiang, Jian,Li, Linlin,Zhang, Lin,Li, Li,Li, Chun
, (2021/03/24)
The Ru-catalyzed asymmetric hydrogenation of ketones with chiral diamine and monodentate achiral phosphine has been developed. A wide range of ketones were hydrogenated to afford the corresponding chiral secondary alcohols in good to excellent enantioselectivities (up to 98.1% ee). In addition, an appropriate mechanism for the asymmetric hydrogenation was proposed and verified by NMR spectroscopy.
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.
RETRACTED ARTICLE: The Manganese(I)-Catalyzed Asymmetric Transfer Hydrogenation of Ketones: Disclosing the Macrocylic Privilege
Passera, Alessandro,Mezzetti, Antonio
supporting information, p. 187 - 191 (2019/12/11)
The bis(carbonyl) manganese(I) complex [Mn(CO)2(1)]Br (2) with a chiral (NH)2P2 macrocyclic ligand (1) catalyzes the asymmetric transfer hydrogenation of polar double bonds with 2-propanol as the hydrogen source. Ketones (43 substrates) are reduced to alcohols in high yields (up to >99 %) and with excellent enantioselectivities (90–99 % ee). A stereochemical model based on attractive CH–π interactions is proposed.
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.
Efficient Asymmetric Synthesis of Ethyl (S)-4-Chloro-3-hydroxybutyrate Using Alcohol Dehydrogenase SmADH31 with High Tolerance of Substrate and Product in a Monophasic Aqueous System
Chen, Rong,Liu, Qinghai,Wang, Hualei,Wei, Dongzhi,Xie, Youyu,Yang, Zeyu,Ye, Wenjie
, p. 1068 - 1076 (2020/07/06)
Bioreductions catalyzed by alcohol dehydrogenases (ADHs) play an important role in the synthesis of chiral alcohols. However, the synthesis of ethyl (S)-4-chloro-3-hydroxybutyrate [(S)-CHBE], an important drug intermediate, has significant challenges concerning high substrate or product inhibition toward ADHs, which complicates its production. Herein, we evaluated a novel ADH, SmADH31, obtained from the Stenotrophomonas maltophilia genome, which can tolerate extremely high concentrations (6 M) of both substrate and product. The coexpression of SmADH31 and glucose dehydrogenase from Bacillus subtilis in Escherichia coli meant that as much as 660 g L-1 (4.0 M) ethyl 4-chloroacetoacetate was completely converted into (S)-CHBE in a monophasic aqueous system with a >99.9% ee value and a high space-time yield (2664 g L-1 d-1). Molecular dynamics simulation shed light on the high activity and stereoselectivity of SmADH31. Moreover, five other optically pure chiral alcohols were synthesized at high concentrations (100-462 g L-1) as a result of the broad substrate spectrum of SmADH31. All these compounds act as important drug intermediates, demonstrating the industrial potential of SmADH31-mediated bioreductions.
