- Decarboxylative Polyfluoroarylation of Alkylcarboxylic Acids
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Polyfluoroarenes are useful building blocks in several areas such as drug discovery, materials, and crop protection. Herein, we report the first polyfluoroarylation of aliphatic carboxylic acids via photoredox decarboxylation. The method proceeds with bro
- Sun, Xiang,Ritter, Tobias
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supporting information
p. 10557 - 10562
(2021/04/05)
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- One-pot Chemoenzymatic Deracemisation of Secondary Alcohols Employing Variants of Galactose Oxidase and Transfer Hydrogenation
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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.
- Yuan, Bo,Debecker, Damien P.,Wu, Xiaofeng,Xiao, Jianliang,Fei, Qiang,Turner, Nicholas J.
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p. 6191 - 6195
(2020/10/15)
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- Asymmetric Hydrogenation of Aryl Perfluoroalkyl Ketones Catalyzed by Rhodium(III) Monohydride Complexes Bearing Josiphos Ligands
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The asymmetric hydrogenation of 2,2,2-trifluoroacetophenones and aryl perfluoroalkyl ketones was developed using a unique, well-defined chloride-bridged dinuclear rhodium(III) complex bearing Josiphos-type diphosphine ligands. These complexes were prepared from [RhCl(cod)]2, Josiphos ligands, and hydrochloric acid. As catalyst precursors, they allow for the efficient and enantioselective synthesis (up to 99 % ee) of chiral secondary alcohols with perfluoroalkyl groups. This system does not require an activating base for the hydrogenation of 2,2,2-trifluoroacetophenones. Additionally, the enantioselective C=O hydrogenations of 2-phenyl-3-(haloacetyl)-indoles, a class of privileged structures in medicinal chemistry, is reported for the first time.
- Brüning, Fabian,Nagae, Haruki,K?ch, Daniel,Mashima, Kazushi,Togni, Antonio
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supporting information
p. 10818 - 10822
(2019/07/31)
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- Asymmetric Magnesium-Catalyzed Hydroboration by Metal-Ligand Cooperative Catalysis
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Asymmetric catalysis with readily available, cheap, and non-toxic alkaline earth metal catalysts represents a sustainable alternative to conventional synthesis methodologies. In this context, we describe the development of a first MgII-catalyzed enantioselective hydroboration providing the products with excellent yields and enantioselectivities. NMR spectroscopy studies and DFT calculations provide insights into the reaction mechanism and the origin of the enantioselectivity which can be explained by a metal-ligand cooperative catalysis pathway involving a non-innocent ligand.
- Falconnet, Alban,Magre, Marc,Maity, Bholanath,Cavallo, Luigi,Rueping, Magnus
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supporting information
p. 17567 - 17571
(2019/11/13)
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- Synthetic method for optical pure penta-fluo-phenethyl alcohol
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The invention relates to resolution of a phenethyl alcohol compound and especially relates to a synthetic method for optical pure penta-fluo-phenethyl alcohol, mainly aiming at solving the technical problems of long synthetic route of a penta-fluo-phenethyl alcohol asymmetric synthesis method and industrial use limitation of an enzymolysis resolution method. According to the technical scheme provided by the invention, the synthetic method for optical pure penta-fluo-phenethyl alcohol comprises the following steps: reducing pentafluoroacetophenone with sodium borohydride, reacting with phthalic anhydride to generate a benzoic acid derivative, and then chemically resolving the benzoic acid derivative with chiral phenylethylamine, removing phenylethylamine with diluted hydrochloric acid, resolving the phthalic acid group with alkali, extracting, drying, filtering and concentrating, thereby acquiring the optical pure penta-fluo-phenethyl alcohol product.
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Paragraph 0013
(2017/08/31)
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- Nickel-catalyzed reduction of ketones with water and triethylsilane
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The acetophenone (1a) reduction using catalytically active nickel complexes and water is an efficient and sustainable method to access a new methodology of transfer hydrogenation of ketones. When triethylsilane (Et3SiH) was used as sacrificial agent to promote the transfer hydrogenation from water, 1-phenylethanol (2a) was obtained in excellent yield along with silanol (Et3SiOH) as the reaction's driving force. Deuterium labeling studies were made using Et3SiD or D2O and these studies showed that both compounds participate as hydride sources for the ketone reduction. A scope of substrates was assessed, including a variety of mono/diketones, and α,β-unsaturated ketones, to yield the corresponding secondary alcohols and saturated ketones. Additionally, asymmetric transfer hydrogenation of mono-ketones was studied for the mixture of nickel/(bisphosphine or phospholane) as catalyst precursor, using H2O/Et3SiO system and ethanol as hydrogen sources.
- Castellanos-Blanco, Nahury,Flores-Alamo, Marcos,García, Juventino J.
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p. 324 - 332
(2017/06/29)
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- C(sp2)-F Oxidative Addition of Fluorinated Aryl Ketones by iPrPCPIr
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The reaction of iPrPCPIrH4 (iPrPCP = κ3-2,6-C6H3(CH2P(iPr)2)2) with ≥2 equiv of 2,3,4,5,6-pentafluoroacetophenone (AP-F5) in aromatic solvents at
- Wilklow-Marnell, Miles,Brennessel, William W.,Jones, William D.
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p. 3125 - 3134
(2017/09/05)
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- Nickel-catalyzed transfer hydrogenation of ketones using ethanol as a solvent and a hydrogen donor
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We report a nickel(0)-catalyzed direct transfer hydrogenation (TH) of a variety of alkyl-aryl, diaryl, and aliphatic ketones with ethanol. This protocol implies a reaction in which a primary alcohol serves as a hydrogen atom source and solvent in a one-pot reaction without any added base. The catalytic activity of the nickel complex [(dcype)Ni(COD)] (e) (dcype: 1,2-bis(dicyclohexyl-phosphine)ethane, COD: 1,5-cyclooctadiene), towards transfer hydrogenation (TH) of carbonyl compounds using ethanol as the hydrogen donor was assessed using a broad scope of ketones, giving excellent results (up to 99% yield) compared to other homogeneous phosphine-nickel catalysts. Control experiments and a mercury poisoning experiment support a homogeneous catalytic system; the yield of the secondary alcohols formed in the TH reaction was monitored by gas chromatography (GC) and NMR spectroscopy.
- Castellanos-Blanco, Nahury,Arévalo, Alma,García, Juventino J.
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p. 13604 - 13614
(2016/09/04)
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- Cyclopentadienyliron dicarbonyl dimer: A simple tool for the hydrosilylation of aldehydes and ketones under air
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The readily available iron complex [CpFe(CO)2]2 (1) exhibits good catalytic activity in the hydrosilylation of aldehydes and ketones in the presence of diethoxymethylsilane. The procedure described is air-tolerant and applicable to a wide range of substrates.
- Jung, Thais Cordeiro,Argouarch, Gilles,Van De Weghe, Pierre
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- Hydrodefluorination of Fluoroarenes Using Hydrogen Transfer Catalysts with a Bifunctional Iridium/NH Moiety
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The hydrodefluorination of fluoroarenes with transfer hydrogenation catalysts using 2-propanol or potassium formate is described. With the aid of metal/NH cooperation, the C-N chelating Ir complexes derived from benzylic amines can efficiently promote the reduction involving the C-F bond cleavage under ambient conditions even in the absence of hydrosilanes or H2 gas, leading to the partially fluorinated products in good yields and with high selectivity.
- Matsunami, Asuka,Kuwata, Shigeki,Kayaki, Yoshihito
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p. 5181 - 5185
(2016/08/18)
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- PRODUCTION METHOD OF OPTICALLY ACTIVE SECONDARY ALCOHOL
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PROBLEM TO BE SOLVED: To provide a chemical catalytic method allowing efficient production of a corresponding optically active secondary alcohol from an aromatic ketone having a substituent at each of two β-positions in an aromatic ring to the carbonyl site, so that both enantiomers can be separately made. SOLUTION: A production method of optically active secondary alcohol is characterized by reacting a ketone compound such as acetophenone derivatives with hydrogen in the presence of a ruthenium complex catalyst having an optically active diphosphine ligand. COPYRIGHT: (C)2015,JPO&INPIT
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Paragraph 0132; 0140; 0141; 0144; 0151
(2016/11/14)
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- Kinetic study on photocatalytic hydrogenation of acetophenone derivatives on titanium dioxide
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Acetophenone (AP) derivatives were photocatalytically hydrogenated to afford the corresponding secondary alcohols with excellent chemical efficiencies on titanium dioxide (Degussa P25, TiO2) under UV light irradiation. Maximum reaction rates (kmax) and apparent adsorption constants (KLH) under irradiation were obtained from the Langmuir-Hinshelwood kinetic analysis. The kmax values showed a tendency to decrease with the decreasing reduction potentials (Ered) of the AP derivatives, while the KLH values were distributed in the range of 280-780 L mol-1. Among these, simple AP exhibited the greatest adsorptivity upon the UV irradiated TiO2 surface. Additionally, it was demonstrated that the electrons trapped at surface defect Ti (Tist) sites on the TiO2 actually hydrogenated the AP derivatives. The amount of reacted electrons also showed a tendency to decrease with decreasing Ered values, in accord with the dependence on kmax. These results indicate that the electrons accumulated at shallow Tist states easily participate in the hydrogenation of AP derivatives, whereas those trapped at deeper states hardly react with the substrates. The results strongly support the electron transfer reaction model via the Tist sites in the photocatalytic hydrogenation on TiO2. This journal is the Partner Organisations 2014.
- Kohtani, Shigeru,Kamoi, Yuna,Yoshioka, Eito,Miyabe, Hideto
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p. 1084 - 1091
(2014/04/03)
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- Dye-sensitized photo-hydrogenation of aromatic ketones on titanium dioxide under visible light irradiation
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Aromatic ketones were photocatalytically hydrogenated on P25 TiO 2 powder modified with metal free organic dyes under visible light irradiation. The suitable combination of dye-TiO2 and triethylamine as a sacrificial electron donor successfully extended the photocatalytic UV response of TiO2 toward visible light region in the photo-hydrogenation of acetophenone derivatives.
- Kohtani, Shigeru,Nishioka, Saki,Yoshioka, Eito,Miyabe, Hideto
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- Copper-catalyzed hydrodefluorination of fluoroarenes by copper hydride intermediates
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Breaking bad: Efficient copper-catalyzed C-F bond activation has been achieved by replacing fluorine with hydrogen. A copper hydride is proposed as the active intermediate, which proceeds through a nucleophilic attack on the fluorocarbon, as determined by experimental and theoretical results (see structure; C gray, H white, Cu light red, F light blue; distances in ?).
- Lv, Hongbin,Cai, Yuan-Bo,Zhang, Jun-Long
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supporting information
p. 3203 - 3207
(2013/04/23)
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- Photocatalytic hydrogenation of acetophenone derivatives and diaryl ketones on polycrystalline titanium dioxide
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In the absence of molecular oxygen, various aromatic ketones such as acetophenone derivatives and diaryl ketones were photocatalytically hydrogenated on polycrystalline titanium dioxide (Degussa P25) under UV light irradiation (> 340 nm). The desired secondary alcohols were obtained with excellent chemical efficiency (almost 100% yields for 10 examples) by choosing ethanol as a sacrificial hole scavenger, which was oxidized into acetaldehyde.
- Kohtani, Shigeru,Yoshioka, Eito,Saito, Kenji,Kudo, Akihiko,Miyabe, Hideto
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experimental part
p. 1049 - 1053
(2010/11/24)
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- Regioselective hydroboration-oxidation and -amination of fluoro-substituted styrenes
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Hydroboration of fluorinated styrenes with common hydroborating agents results in polymerization. However, regioselective hydroboration has been achieved by utilizing iodoborane-dimethyl sulfide. A series of fluorinated β-phenethyl alcohols and amines were synthesized via this methodology.
- Ramachandran, P. Veeraraghavan,Madhi, Sateesh,O'Donnell, Martin J.
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p. 1252 - 1255
(2008/09/20)
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- Investigation of the factors controlling the regioselectivity of the hydroboration of fluoroolefins
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Either Markovnikov or anti-Markovnikov regioselectivity can be achieved at will during the hydroboration-oxidation of perfluoroalkyl(aryl)ethylenes by varying the hydroborating agent.
- Ramachandran, P. Veeraraghavan,Jennings, Michael P.
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p. 386 - 387
(2007/10/03)
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- Critical role of catalysts and boranes for controlling the regioselectivity in the rhodium-catalyzed hydroboration of fluoroolefins
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(formula presented) Catalytic hydroboration of perfluoroalkylethylenes (RFCH=CH2) with cationic and neutral rhodium complexes allows for selective access to either regioisomeric alcohol after hydroboration with catechol- and pinacolboranes, followed by oxidation with alkaline hydrogen peroxide.
- Ramachandran, P. Veeraraghavan,Jennings, Michael P.,Brown, Herbert C.
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p. 1399 - 1402
(2008/02/09)
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- Markovnikov hydroboration of perfluoroalkylethylenes
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A Markovnikov regioselectivity of 92% or higher is achieved in the hydroboration of a series of perfluoroalkylethylenes and 2',3',4',5',6'- pentafluorostyrene with dichloro- and dibromoborane to provide the corresponding (fluoroalkyl)dihaloboranes (see reaction).
- Brown, Herbert C.,Chen, Guang-Ming,Jennings, Michael P.,Ramachandran, P. Veeraraghavan
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p. 2052 - 2054
(2007/10/03)
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- Cyclic Organotin Lewis Acids
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The Ph3P=O IR frequency shift method has been used to compare the Lewis acid strength of several cyclic organotin dichlorides.Structures 3, 20, and 4 are relatively weak Lewis acids, less potent than Bu2SnCl2, according to the IR criterion.Steric factors appear largely responsible for the decreased Lewis acidity, altough bond angle strain may also contribute in the case of 3.Introduction of electronegative substituents into the aromatic ring of structures related to 4 results in stronger Lewis acids 8 and 18, both of which are relatively more potent than Ph2SnCl2.Methods for the preparation of precursors to the fluorinated 8 and 18 are described, based on the deprotonation of tetrafluoroaryl precursors.
- Vedejs, E.,Erdman, D. E.,Powell, D. R.
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p. 2840 - 2845
(2007/10/02)
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- Photosubstitution reactions on aromatic and heteroaromatic rings evidence for addition and substitution mechanism
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Irradiation of a cyclohexane solution of hexafluorobenzene in the presence of benzophenone resulted in both, substitution and addition products. Similar photoreaction has been observed by irradiation of hexafluorobenzene in some alcohols in the presence of benzophenone. The reaction of pentafluorobenzene with methanol or cyclohexane resulted in the substitution of a 2-or 4-fluoro atom, while the reaction of pentafluoroanisole resulted in the formation of o-, m- and p-isomers. Irradiation of a cyclohexane solution or of an alcohol solution of octafluoronaphthalene yielded 1- and 2-substituted products. On the other hand, the photosubstitution of fluorine atom in pentafluoropyridine took place exclusively at the position four, thus forming 4-cyclohexyl or 4-(1-hydroxyalkyl) substituted products.
- Sket, Boris,Zupan, Marko,Zupancic, Natasa,Pahor, Barbara
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p. 5029 - 5042
(2007/10/02)
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