4654-39-1Relevant articles and documents
Regiodivergent Reductive Opening of Epoxides by Catalytic Hydrogenation Promoted by a (Cyclopentadienone)iron Complex
De Vries, Johannes G.,Gandini, Tommaso,Gennari, Cesare,Jiao, Haijun,Pignataro, Luca,Stadler, Bernhard M.,Tadiello, Laura,Tin, Sergey
, p. 235 - 246 (2022/01/03)
The reductive opening of epoxides represents an attractive method for the synthesis of alcohols, but its potential application is limited by the use of stoichiometric amounts of metal hydride reducing agents (e.g., LiAlH4). For this reason, the corresponding homogeneous catalytic version with H2 is receiving increasing attention. However, investigation of this alternative has just begun, and several issues are still present, such as the use of noble metals/expensive ligands, high catalytic loading, and poor regioselectivity. Herein, we describe the use of a cheap and easy-To-handle (cyclopentadienone)iron complex (1a), previously developed by some of us, as a precatalyst for the reductive opening of epoxides with H2. While aryl epoxides smoothly reacted to afford linear alcohols, aliphatic epoxides turned out to be particularly challenging, requiring the presence of a Lewis acid cocatalyst. Remarkably, we found that it is possible to steer the regioselectivity with a careful choice of Lewis acid. A series of deuterium labeling and computational studies were run to investigate the reaction mechanism, which seems to involve more than a single pathway.
Molybdenum tricarbonyl complex functionalised with a molecular triazatriangulene platform on Au(111): Surface spectroscopic characterisation
Petersen, Finn,Lautenschl?ger, Irene,Schlimm, Alexander,Fl?ser, Benedikt M.,Jacob, Hanne,Amirbeigiarab, Reihaneh,Rusch, Talina R.,Strunskus, Thomas,Magnussen, Olaf,Tuczek, Felix
, p. 1042 - 1052 (2021/02/03)
Transition metal complexes form the basis for small molecule activation and are relevant for electrocatalysis. To combine both approaches the attachment of homogeneous catalysts to metallic surfaces is of significant interest. Towards this goal a molybdenum tricarbonyl complex supported by a tripodal phosphine ligand was covalently bound to a triazatriangulene (TATA) platform via an acetylene unit and the resulting TATA-functionalised complex was deposited on a Au(111) surface. The corresponding self-assembled monolayer was characterised with scanning tunnelling microscopy (STM), X-ray photoelectron spectroscopy (XPS), and near-edge X-ray absorption fine structure (NEXAFS). The vibrational properties of the surface-adsorbed complexes were investigated with the help of infrared reflection absorption spectroscopy (IRRAS), and the frequency/intensity changes with respect to the bulk spectrum were analysed. A full vibrational analysis was performed with the help of DFT.
Tropylium-Promoted Hydroboration Reactions: Mechanistic Insights Via Experimental and Computational Studies
Mai, Binh Khanh,Nguyen, Thanh Vinh,Ton, Nhan N. H.
, p. 9117 - 9133 (2021/07/19)
Hydroboration reaction of alkynes is one of the most synthetically powerful tools to access organoboron compounds, versatile precursors for cross-coupling chemistry. This type of reaction has traditionally been mediated by transition-metal or main group catalysts. Herein, we report a novel method using tropylium salts, typically known as organic oxidants and Lewis acids, to promote the hydroboration reaction of alkynes. A broad range of vinylboranes can be easily accessed via this metal-free protocol. Similar hydroboration reactions of alkenes and epoxides can also be efficiently catalyzed by the same tropylium catalysts. Experimental studies and DFT calculations suggested that the reaction follows an uncommon mechanistic pathway, which is triggered by the hydride abstraction of pinacolborane with tropylium ion. This is followed by a series ofin situcounterion-activated substituent exchanges to generate boron intermediates that promote the hydroboration reaction.
Enantioselective Copper(I)/Chiral Phosphoric Acid Catalyzed Intramolecular Amination of Allylic and Benzylic C?H Bonds
Ye, Liu,Tian, Yu,Meng, Xiang,Gu, Qiang-Shuai,Liu, Xin-Yuan
supporting information, p. 1129 - 1133 (2019/12/12)
Radical-involved enantioselective oxidative C?H bond functionalization by a hydrogen-atom transfer (HAT) process has emerged as a promising method for accessing functionally diverse enantioenriched products, while asymmetric C(sp3)?H bond amination remains a formidable challenge. To address this problem, described herein is a dual CuI/chiral phosphoric acid (CPA) catalytic system for radical-involved enantioselective intramolecular C(sp3)?H amination of not only allylic positions but also benzylic positions with broad substrate scope. The use of 4-methoxy-NHPI (NHPI=N-hydroxyphthalimide) as a stable and chemoselective HAT mediator precursor is crucial for the fulfillment of this transformation. Preliminary mechanistic studies indicate that a crucial allylic or benzylic radical intermediate resulting from a HAT process is involved.
Erbium-Catalyzed Regioselective Isomerization-Cobalt-Catalyzed Transfer Hydrogenation Sequence for the Synthesis of Anti-Markovnikov Alcohols from Epoxides under Mild Conditions
Liu, Xin,Longwitz, Lars,Spiegelberg, Brian,T?njes, Jan,Beweries, Torsten,Werner, Thomas
, p. 13659 - 13667 (2020/11/30)
Herein, we report an efficient isomerization-transfer hydrogenation reaction sequence based on a cobalt pincer catalyst (1 mol %), which allows the synthesis of a series of anti-Markovnikov alcohols from terminal and internal epoxides under mild reaction conditions (≤55 °C, 8 h) at low catalyst loading. The reaction proceeds by Lewis acid (3 mol % Er(OTf)3)-catalyzed epoxide isomerization and subsequent cobalt-catalyzed transfer hydrogenation using ammonia borane as the hydrogen source. The general applicability of this methodology is highlighted by the synthesis of 43 alcohols from epoxides. A variety of terminal (23 examples) and 1,2-disubstituted internal epoxides (14 examples) bearing different functional groups are converted to the desired anti-Markovnikov alcohols in excellent selectivity and yields of up to 98%. For selected examples, it is shown that the reaction can be performed on a preparative scale up to 50 mmol. Notably, the isomerization step proceeds via the most stable carbocation. Thus, the regiochemistry is controlled by stereoelectronic effects. As a result, in some cases, rearrangement of the carbon framework is observed when tri-and tetra-substituted epoxides (6 examples) are converted. A variety of functional groups are tolerated under the reaction conditions even though aldehydes and ketones are also reduced to the respective alcohols under the reaction conditions. Mechanistic studies and control experiments were used to investigate the role of the Lewis acid in the reaction. Besides acting as the catalyst for the epoxide isomerization, the Lewis acid was found to facilitate the dehydrogenation of the hydrogen donor, which enhances the rate of the transfer hydrogenation step. These experiments additionally indicate the direct transfer of hydrogen from the amine borane in the reduction step.
Regioselective Halogenation of Arenes and Heterocycles in Hexafluoroisopropanol
Tang, Ren-Jin,Milcent, Thierry,Crousse, Benoit
, p. 930 - 938 (2018/01/28)
Regioselective halogenation of arenes and heterocycles with N-halosuccinimides in fluorinated alcohols is disclosed. Under mild condition reactions, a wide diversity of halogenated arenes are obtained in good yields with high regioselectivity. Additionally, the versatility of the method is demonstrated by the development of one-pot sequential halogenation and halogenation-Suzuki cross-coupling reactions.
Antiproliferative activity and SARs of caffeic acid esters with mono-substituted phenylethanols moiety
Xie, Jin,Yang, Fengzhi,Zhang, Man,Lam, Celine,Qiao, Yixue,Xiao, Jia,Zhang, Dongdong,Ge, Yuxuan,Fu, Lei,Xie, Dongsheng
, p. 131 - 134 (2016/12/27)
A series of CAPE derivatives with mono-substituted phenylethanols moiety were synthesized and evaluated by MTT assay on growth of 4 human cancer cell lines (Hela, DU-145, MCF-7 and ECA-109). The substituent effects on the antiproliferative activity were systematically investigated for the first time. It was found that electron-donating and hydrophobic substituents at 2′-position of phenylethanol moiety could significantly enhance CAPE's antiproliferative activity. 2′-Propoxyl derivative, as a novel caffeic acid ester, exhibited exquisite potency (IC50?=?0.4?±?0.02 & 0.6?±?0.03?μM against Hela and DU-145 respectively).
Preparation method for hemihydrate lorcaserin hydrochloride
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Paragraph 0133; 0134, (2017/08/28)
The invention discloses a preparation method for hemihydrate lorcaserin hydrochloride. The preparation method comprises the following steps: (1) making a compound shown as a formula III react with ammonia to obtain a compound shown as a formula II; (2) under the protection of nitrogen gas, dissolving the compound shown as the formula II in an organic solvent, adding a hydrogen chloride solution of which the solvent is the organic solvent to salify, and adding water and cyclohexane to form a hemihydrate in order to obtain the compound shown as a formula I, wherein the organic solvent is isopropanol or 1,4-dioxane. In the preparation method disclosed by the invention, ammonium hydroxide substitutes for potassium carbonate in the prior art, so that unqualified ignition residues of a finial product caused by potassium chloride generated after salt removal can be avoided; an isopropoxide hydrochloride solution substitutes for the conventional hydrogen chloride gas, so that other impurities can be prevented from being introduced in a preparation process under the improper control of dosage and rate of the gas.
Regioselective hydrosilylation of epoxides catalysed by nickel(II) hydrido complexes
Wenz, Jan,Wadepohl, Hubert,Gade, Lutz H.
, p. 4308 - 4311 (2017/04/21)
Bench-stable nickel fluoride complexes bearing NNN pincer ligands have been employed as precursors for the regioselective hydrosilylation of epoxides at room temperature. A nickel hydride assisted epoxide opening is followed by the cleavage of the newly formed nickel oxygen bond by σ-bond metathesis with a silane.
Nucleophilic addition of arylmethylzinc reagents (ArCH2ZnCl) to formaldehyde: An easy access to 2-(hetro)arylethyl alcohols
Bhatt,Samant,Pednekar, Suhas
supporting information, p. 968 - 974 (2017/05/04)
The selective addition of arylmethylmagnesium halides with formaldehyde giving arylethyl alcohols is extremely challenging. To circumvent the difficulties, in the current communication, we have reported on the nucleophilic addition of benzyl zinc reagents derived from inexpensive and abundant benzyl chlorides to paraformaldehyde. The reaction investigated herein is hitherto unknown and was found to be selective, operationally simple, atom- and step-economical and high yielding to deliver phenethyl alcohols utilized as key perfumery ingredients in 60–83% yields. After successful establishment of the reaction condition, the reaction was also scaled up successfully to deliver a large-scale preparation of the phenethyl alcohol.
