- Epoxide Electroreduction
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Selective hydrogenation of epoxides would be a direct and powerful approach for alcohol synthesis, but it has proven to be elusive. Here, electrochemically epoxide hydrogenation using electrons and protons as reductants is reported. A wide range of primary, secondary, and tertiary alcohols can be achieved through selective Markovnikov or anti-Markovnikov ring opening in the absence of transition metals. Mechanistic investigations revealed that the regioselectivity is controlled by the thermodynamic stabilities of the in situ generated benzyl radicals for aryl-substituted epoxides and the kinetic tendency for Markovnikov selective ring opening for alkyl-substituted epoxides.
- Huang, Cheng,Lu, Qingquan,Ma, Wan,Qi, Xiaotian,Xu, Minghao,Zheng, Xuelian
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p. 1389 - 1395
(2022/01/19)
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- Regiodivergent Reductive Opening of Epoxides by Catalytic Hydrogenation Promoted by a (Cyclopentadienone)iron Complex
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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.
- Tadiello, Laura,Gandini, Tommaso,Stadler, Bernhard M.,Tin, Sergey,Jiao, Haijun,de Vries, Johannes G.,Pignataro, Luca,Gennari, Cesare
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p. 235 - 246
(2022/01/03)
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- Selective A2A receptor antagonist
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The invention provides a selective A2A receptor antagonist. In specific, the invention provides the selective A2A receptor antagonist shown in the formula (I), a drug composition containing the same and the pharmacy application and treatment application t
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Paragraph 0123-0125; 0127
(2018/12/14)
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- Antiproliferative activity and SARs of caffeic acid esters with mono-substituted phenylethanols moiety
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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).
- Xie, Jin,Yang, Fengzhi,Zhang, Man,Lam, Celine,Qiao, Yixue,Xiao, Jia,Zhang, Dongdong,Ge, Yuxuan,Fu, Lei,Xie, Dongsheng
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supporting information
p. 131 - 134
(2016/12/27)
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- A General, Practical Triethylborane-Catalyzed Reduction of Carbonyl Functions to Alcohols
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A combination of the abundant and low-cost triethylborane and sodium alkoxide generates a highly efficient catalyst for reduction of esters, as well as ketones and aldehydes, to alcohols using an inexpensive hydrosilane under mild conditions. The catalyst system exhibits excellent chemoselectivity and a high level of functional group tolerance. Mechanistic studies revealed a resting state of sodium triethylalkoxylborate that is the product of the reaction of BEt3 with sodium alkoxide. This borate species reacts with hydrosilane to form NaBEt3H, which rapidly reduces esters.
- Peng, Dongjie,Zhang, Mintao,Huang, Zheng
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supporting information
p. 14737 - 14741
(2015/10/19)
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- Indole derivatives and pharmaceutical composition comprising the same for treating or preventing disease related to RAGE
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A novel indole-based derivative acceptable salt, and manufacturing method thereof including RAGE associated pharmaceutical composition for the prevention or the treatment of disorders the disclosure. Herein a derivative indole-based according to by antagonism in RAGE, nerve cells with the Amyloid-beta peptide loses purpose: a method of fabricating a apparatus move into brain, Alzheimer's disease associated RAGE disease, cerebrovascular dementia, dementia due to damage bean curd, multi blockade dementia, Alzheimer's disease or the like dementia alcoholic or mixed dementia multi blockade and including dementia, pick (pick) bottle, a smartcrew [...] -Jakob (Creutzfeldt-jakob) bottle, that thyroid gland symptoms , bean curd a blade Parkinson (Parkinson) bottle, Huntington's disease (Huntington) which is useful in preventing or treating, can be used.
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Paragraph 0635-0640
(2021/10/25)
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- Continuous-flow synthesis of monoarylated acetaldehydes using aryldiazonium salts
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Anilines and ethyl vinyl ether can be used as precursors for a process that is the synthetic equivalent of the α-arylation of acetaldehyde enolate. The reaction manifests a high level of functional group compatibility, allowing the ready preparation of a number of synthetically valuable compounds.
- Chernyak, Natalia,Buchwald, Stephen L.
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p. 12466 - 12469
(2012/09/05)
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- Smiles-type free radical rearrangement of aromatic sulfonates and sulfonamides: Syntheses of arylethanols and arylethylamines
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Smiles-type free radical rearrangements of arenesulfonates and arenesulfonamides are exploited for synthetic purposes. 4-Substituted benzenesulfonates cause Smiles-type rearrangement only when substituted by an electron withdrawing group. Therefore, ipso-sttack by an alkyl radical on arenesulfonates takes place in an electrophilic manner. Arenesulfonamides rearrange only when the amide nitrogen is substituted by an alkoxycarbonyl group, due to the electron withdrawing nature of this group. Sulfonates and the N-ethoxycarbonylsulfonamide derivatives of naphthalene, quinoline, and thiophene cause more rearrangement and show synthetic utility. Aromatic amino acid analogues were synthesized by Smiles-type rearrangement with moderate yields. The radical Smiles-type rearrangement of sulfonate and sulfonamide derivatives can be a useful synthetic route when we understand the electronic character of these reactions.
- Tada, Masaru,Shijima, Hiroyasu,Nakamura, Masaharu
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p. 2499 - 2505
(2007/10/03)
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- General Base Catalysis, Structure-Reactivity interactions, and Merging of Mechanisms for Elimination Reactions of (2-Arylethyl)quinuclidinium Ions
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Structure-reactivity parameters and interaction coefficients are reported for elimination reactions of N-(2-arylethyl)quinuclidinium ions and for 2-arylethyl halides and tosylates in 60percent Me2SO/wares at 40 deg C, based on direct measurements of Bronsted β values for general base catalysis by oxyanion buffers, Hammet ρ values, and β1g for substituted quinuclidines.The Bronsted slopes increase from β - 0.67 for N-(2-(p-nitrophenyl)ethyl)quinuclidinium ions, which react by an E1cBirr mechanism, to β ca. 0.9 for the reactions of other N-(2-arylethyl)quinuclidinium ions by a concerted E2 elimination.There is no detectable interaction between the base catalyst and the leaving group for E1cB elimination, so that the interaction coefficient pxy = dβ1g/dpKBH = dβ/dpK1g is ca.0 for the N-(2-(p-nitrophenyl)ethyl)quinuclidinium ions.In contrast, values of β1g become less negative with increasing pKa of the base catalyst for the p-cyano and other N-(2-arylethyl)quinuclidinium ions, giving a constant value of pxy = 0.018 for the E2 elimination reactions of these compounds.The positive pxy coefficient for the N-(2-phenylethyl)quinuclidinium ions is confirmed by the observation of less negative values of β1g as the effective basicity of aqueous tetramethylammonium hydroxyde is increased by the addition of Me2SO.An increase in β with poorer leaving groups in the series of 2-(p-nitrophenyl)ethyl halides also corresponds to a positive pxy coefficient and an E2 mechanism.The interaction between the leaving group and central atoms is shown by the less negative values of β1g with electron-withdrawing substituents on the β-phenyl group, which corresponds to a negative coefficient pyy' = -dβ1g/d?- = -dρ/dpK1g = -0.09.A small decrease in β with electron-withdrawing substituents on the β-phenyl group suggests an interaction between the base catalyst and the central atoms that is described by a negative coefficient pxy' = dβ/d?- = dρ/dpKBH = -0.07.The sign of the pyy' and pxy' coefficient are consistent with an important component of proton transfer in the transition state.These properties of the E2 elimination reactions of N-(2-arylethyl)quinuclidinium ions can be described by a reaction coordinate that is rotated 24 deg counterclockwise from the x coordinate (for proton transfer) on a reaction coordinate-energy diagram that is defined by the observed structure-reactivity parameters.In contrast, β increases with increasing ? for elimination reactions of 2-arylethyl bromides with a positive value of pxy' = 0.07.This suggests more diagonal character to the transition state on the reaction coordinate diagram.The change from E1cB to an E2 mechanism is more easily described as a transformation of mechanism than as a change between two coexisting mechanisms.
- Gandler, Joseph R.,Jencks, William P.
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p. 1937 - 1951
(2007/10/02)
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- Synthesis of 4-(4-Amidinophenyl)-2-arylsulphonylaminobutyric Acid Amides
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4-(4-Amidinophenyl)-2-arylsulphonylaminobutyric acid amides with differing amide and arylsulphonyl components were synthetized to test their inhibitory activity against serine proteinases.For the purpose of preparing these compounds, β-(4-cyanophenyl)ethylbromide (5) was reacted with acetaminomalonic acid diethyl ester to give 6, the acid hydrolysis of which yielded predominantly 4-(4-carbamoylphenyl)-2-aminobutyric acid (7).The simultaneously formed dicarboxylic acid 9 was separated after N-arylsulphonylation.The reaction of the N-arylsulphonylated acids 10-15 with thionyl chloride afforded acid chlorides (16-18) with a cyano function from which carboxylic acid amides (19-39) were obtained by reaction with diffrent amines.These compounds were converted into the hydroiodides of the compounds named in the title via the thioamides and the thioimidic acid ester hydroiodides.
- Wagner, G.,Vieweg, H.
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- Nucleotide. XIV. Substituierte β-Phenylaethyl-Gruppen. Neue Schutzgruppen fuer Oligonucleotid-Synthesen nach dem Phosphorsaeuretriester-Verfahren
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Various o- and p-substituted β-phenylethanols (2-10) have been synthesized and investigated as blocking groups in the phosphotriester approach.A large number of 5'-O-tritylated thymidine-3'-phosphotriesters (13-36) with two different phosphate protecting groups have been prepared, characterized, and studied according to their chemical stability and usefullness for oligonucleotide syntheses.The combination of a 5'-O-monomethoxytrityl- and a 3'-(2,5-dichlorophenyl, p-nitrophenylethyl)-phosphate function as in 18 turned out to possess optimal properties as a monomeric nucleotide building block due to the fact that these blocking groups can be quantitatively and selectively be removed without harming each other by trifluoroacetic acid in chloroform to 41, by oximate to 42, and by DBU to 43.The base-catalyzed removal of the monosubstituted phenylethyl groups by DBU or DBN respectively as well as the disubstituted phenylethyl groups by triethylamine in aprotic solvents is a β-elimination process leading to phosphodiesters without attack on the P-center.
- Uhlmann, Eugen,Pfleiderer, Wolfgang
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p. 1688 - 1703
(2007/10/02)
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