- Green Esterification of Carboxylic Acids Promoted by tert-Butyl Nitrite
-
In this work, the green esterification of carboxylic acids promoted by tert-butyl nitrite has been well developed. This transformation is compatible with a broad range of substrates and exhibits excellent functional group tolerance. Various drugs and substituted amino acids are applicable to this reaction under near neutral conditions, with good to excellent yields.
- Cheng, Xionglve,Jiang, Gangzhong,Li, Xingxing,Tao, Suyan,Wan, Xiaobing,Zhao, Yanwei,Zheng, Yonggao
-
supporting information
p. 2713 - 2718
(2021/06/25)
-
- Iodoarene-Catalyzed Oxyamination of Unactivated Alkenes to Synthesize 5-Imino-2-Tetrahydrofuranyl Methanamine Derivatives
-
Reported here is the room-temperature metal-free iodoarene-catalyzed oxyamination of unactivated alkenes. In this process, the alkenes are difunctionalized by the oxygen atom of the amide group and the nitrogen in an exogenous HNTs2 molecule. This mild and open-air reaction provided an efficient synthesis to N-bistosyl-substituted 5-imino-2-tetrahydrofuranyl methanamine derivatives, which are important motifs in drug development and biological studies. Mechanistic study based on experiments and density functional theory calculations showed that this transformation proceeds via activation of the substrate alkene by an in situ generated cationic iodonium(III) intermediate, which is subsequently attacked by an oxygen atom (instead of nitrogen) of amides to form a five-membered ring intermediate. Finally, this intermediate undergoes an SN2 reaction by NTs2 as the nucleophile to give the oxygen and nitrogen difunctionalized 5-imino-2-tetrahydrofuranyl methanamine product. An asymmetric variant of the present alkene oxyamination using chiral iodoarenes as catalysts also gave promising results for some of the substrates.
- Deng, Xiao-Jun,Liu, Hui-Xia,Zhang, Lu-Wen,Zhang, Guan-Yu,Yu, Zhi-Xiang,He, Wei
-
p. 235 - 253
(2021/01/09)
-
- Visible-light photoredox-catalyzed selective carboxylation of C(sp3)?F bonds with CO2
-
It is highly attractive and challenging to utilize carbon dioxide (CO2), because of its inertness, as a nontoxic and sustainable C1 source in the synthesis of valuable compounds. Here, we report a novel selective carboxylation of C(sp3)?F bonds with CO2 via visible-light photoredox catalysis. A variety of mono-, di-, and trifluoroalkylarenes as well as α,α-difluorocarboxylic esters and amides undergo such reactions to give important aryl acetic acids and α-fluorocarboxylic acids, including several drugs and analogs, under mild conditions. Notably, mechanistic studies and DFT calculations demonstrate the dual role of CO2 as an electron carrier and electrophile during this transformation. The fluorinated substrates would undergo single-electron reduction by electron-rich CO2 radical anions, which are generated in situ from CO2 via sequential hydride-transfer reduction and hydrogen-atom-transfer processes. We anticipate our finding to be a starting point for more challenging CO2 utilization with inert substrates, including lignin and other biomass.
- Bo, Zhi-Yu,Chen, Lin,Gao, Tian-Yu,Jing, Ke,Lan, Yu,Liu, Shi-Han,Luo, Shu-Ping,Yan, Si-Shun,Yu, Bo,Yu, Da-Gang
-
supporting information
p. 3099 - 3113
(2021/11/16)
-
- Boryl Radical Activation of Benzylic C-OH Bond: Cross-Electrophile Coupling of Free Alcohols and CO2via Photoredox Catalysis
-
A new strategy for the direct cleavage of the C(sp3)-OH bond has been developed via activation of free alcohols with neutral diphenyl boryl radical generated from sodium tetraphenylborate under mild visible light photoredox conditions. This strategy has been verified by cross-electrophile coupling of free alcohols and carbon dioxide for the synthesis of carboxylic acids. Direct transformation of a range of primary, secondary, and tertiary benzyl alcohols to acids has been achieved. Control experiments and computational studies indicate that activation of alcohols with neutral boryl radical undergoes homolysis of the C(sp3)-OH bond, generating alkyl radicals. After reducing the alkyl radical into carbon anion under photoredox conditions, the following carboxylation with CO2 affords the coupling product.
- Jiang, Yi-Qian,Lan, Yu,Li, Shi-Jun,Li, Wen-Duo,Li, Yan-Lin,Wu, Yang,Xia, Ji-Bao
-
-
- Photoredox Catalytic Phosphite-Mediated Deoxygenation of α-Diketones Enables Wolff Rearrangement and Staudinger Synthesis of β-Lactams
-
A novel visible-light-driven catalytic activation of C=O bonds by exploiting the photoredox chemistry of 1,3,2-dioxaphospholes, readily accessible from α-diketones and trialkyl phosphites, is reported. This mild and environmentally friendly strategy provides an unprecedented and efficient access to the Wolff rearrangement reaction which traditionally entails α-diazoketones as precursors. The resulting ketenes could be precisely trapped by alcohols/thiols to give α-aryl (thio)acetates and by imines to afford the valuable β-lactams in up to 99 % yields.
- Jiang, Zhiyong,Li, Haijun,Wei, Guo,Yang, Hui
-
supporting information
p. 19696 - 19700
(2021/08/03)
-
- Time-Economical Synthesis of Diarylacetates Enabled by TfOH-Catalyzed Arylation of α-Aryl-α-Diazoesters with Arenes
-
Diarylacetates are privileged structures of many bioactive natural products and pharmaceutical compounds. A time-economical synthesis of diarylacetates by TfOH-catalyzed arylation of α-aryl-α-diazoesters with arenes is described. This protocol provides a variety of diarylacetates in good yields with broad substrate scope, excellent functional group compatibility, and mild reaction conditions. Also, a new mechanism for the arylation reaction of α-aryl-α-diazoesters with arenes under TfOH catalysis is presented.
- Hu, Sha,Wu, Jiale,Lu, Zuolin,Wang, Jiaqi,Tao, Yuan,Jiang, Meifen,Chen, Fener
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p. 2559 - 2563
(2021/04/09)
-
- Asymmetric Intramolecular Hydroalkoxylation of Unactivated Alkenes Catalyzed by Chiral N-Triflyl Phosphoramide and TiCl4?
-
By using a combination of a chiral N-triflyl phosphoramide and TiCl4 as the catalyst, a new process for asymmetric intramolecular hydroalkoxylation of unactivated alkenes was developed, producing various chiral tetrahydrofuran derivatives in 51%—99% yields with 30%—71% ee's.
- Cheng, Aolin,Li, Yingkun,Ma, Jiguo,Wang, Xinxu,Zhang, Yi,Zhao, Baoguo,Zhao, Guoqing,Zhao, Pengyuan
-
supporting information
p. 565 - 569
(2020/04/23)
-
- mCPBA-mediated dioxygenation of unactivated alkenes for the synthesis of 5-imino-2-tetrahydrofuranyl methanol derivatives
-
A mCPBA-mediated, metal-free, intramolecular dioxygenation reaction of unactivated alkenes is reported. In the presence of m-chlorobenzoic peracid, different unsaturated amide substrates could be cyclized via epoxide intermediates, producing the corresponding 5-imino-2-tetrahydrofuranyl methanol products in up to 94% yield at room temperature.
- Deng, Xiaojun,Zhang, Luwen,Liu, Huixia,Bai, Yu,He, Wei
-
supporting information
(2020/11/24)
-
- Metal Free, Direct and Selective Deoxygenation of α-Hydroxy Carbonyl Compounds: Access to α,α-Diaryl Carbonyl Compounds
-
An efficient, metal free, direct and selective deoxygenation of α-hydroxy carbonyl compounds is achieved with the aid of catalytic amount of aqueous HClO4 (70 %) and triethylsilane as hydride source. A variety of α-hydroxy-α,α-diaryl carbonyl compounds are selectively deoxygenated to give α,α-diaryl carbonyl compounds in good to excellent yields. Intermediacy of α-keto carbenium ion is proposed on the basis of some control experiments and atmospheric pressure chemical ionization mass spectral analysis.
- Kumar, Anil,Sandeep,Venugopalan, Paloth
-
-
- Room Temperature Coupling of Aryldiazoacetates with Boronic Acids Enhanced by Blue Light Irradiation
-
A visible-light-promoted photochemical protocol is reported for the coupling of aryldiazoacetates with boronic acids. This photochemical reaction shows great enhancement compared to the same protocol performed in the absence of light. Except for a few cases, the room temperature coupling in the dark (thermal process) generally does not work. When it does, it is likely to also involve free carbenes as key intermediates. Alternatively, photochemical reactions show a broad scope, can be performed under air and tolerate a wide variety of functional groups. Reaction-evolution monitoring, DFT calculations and control experiments have been used to evaluate the main aspects of this intricate mechanistic scenario. Biologically active molecules Adiphenine, Benactyzine and Aprophen have been prepared as examples of synthetic applications.
- da Silva, Amanda F.,Afonso, Marco A. S.,Cormanich, Rodrigo A.,Jurberg, Igor D.
-
supporting information
p. 5648 - 5653
(2020/04/22)
-
- Achiral Derivatives of Hydroxamate AR-42 Potently Inhibit Class i HDAC Enzymes and Cancer Cell Proliferation
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AR-42 is an orally active inhibitor of histone deacetylases (HDACs) in clinical trials for multiple myeloma, leukemia, and lymphoma. It has few hydrogen bond donors and acceptors but is a chiral 2-arylbutyrate and potentially prone to racemization. We report achiral AR-42 analogues incorporating a cycloalkyl group linked via a quaternary carbon atom, with up to 40-fold increased potency against human class I HDACs (e.g., JT86, IC50 0.7 nM, HDAC1), 25-fold increased cytotoxicity against five human cancer cell lines, and up to 70-fold less toxicity in normal human cells. JT86 was ninefold more potent than racAR-42 in promoting accumulation of acetylated histone H4 in MM96L melanoma cells. Molecular modeling and structure-activity relationships support binding to HDAC1 with tetrahydropyran acting as a hydrophobic shield from water at the enzyme surface. Such potent inhibitors of class I HDACs may show benefits in diseases (cancers, parasitic infections, inflammatory conditions) where AR-42 is active.
- Tng, Jiahui,Lim, Junxian,Wu, Kai-Chen,Lucke, Andrew J.,Xu, Weijun,Reid, Robert C.,Fairlie, David P.
-
supporting information
p. 5956 - 5971
(2020/06/05)
-
- Catalytic C-C coupling of diazo compounds with arylboronic acids: Using surface modified sewage sludge as catalyst
-
A green, mild and efficient synthesis of diarylmethines using sewage sludge-derived carbonaceous materials (SW) by perchloric acid catalyzed coupling reactions between diazo compounds and arylboronic acids was developed. The reaction shows a high level of functional tolerance and a broad substrate scope. Furthermore, the highly selective 1,2-alkyl shift products were furnished through the sterically demanding R4, R5 migration of diazo compounds (3-diazochromanone). The structures of 1,2-shift products have been further confirmed by single-crystal X-ray analysis. Significantly, the synthesis of the core structures of darifenacin (a clinical drug for overactive bladder syndrome, OAB) and diclofensine (a stimulant drug showing antidepressant and monoamine reuptake inhibitor activity) further demonstrated the efficacy and synthetic potential of this method. This journal is
- Huang, Fei,Huang, He,Hughes, Timothy,Xie, Yuxing,Xu, Jun,Yu, Yang,Zhang, Zhipeng
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p. 4165 - 4173
(2020/07/14)
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- Copper-Catalyzed Modular Amino Oxygenation of Alkenes: Access to Diverse 1,2-Amino Oxygen-Containing Skeletons
-
Copper-catalyzed alkene amino oxygenation reactions using O-acylhydroxylamines have been achieved for a rapid and modular access to diverse 1,2-amino oxygen-containing molecules. This transformation is applicable to the use of alcohols, carbonyls, oximes, and thio-carboxylic acids as nucleophiles on both terminal and internal alkenes. Mild reaction conditions tolerate a wide range of functional groups, including ether, ester, amide, carbamate, and halide. The reaction protocol allows for starting with free amines as the precursor of O-benzoylhydroxylamines to eliminate their isolation and purification, contributing to broader synthetic utilities. Mechanistic investigations reveal the amino oxygenation reactions may involve distinct pathways, depending on different oxygen nucleophiles.
- Hemric, Brett N.,Chen, Andy W.,Wang, Qiu
-
supporting information
p. 1468 - 1488
(2019/01/25)
-
- Cobalt-catalyzed cyclization with the introduction of cyano, acyl and aminoalkyl groups
-
An efficient synthesis of carbo-and heterocycles using CC, CO and CN bonds under cobalt catalysis is described. The substituents on olefins are key for controlling the regio-and chemoselectivity in the initial hydrogen atom transfer step and quaternary carbons are efficiently constructed under mild conditions. Cyclopropane cleavage and tandem cyclization give highly functionalized bicyclic skeletons in a single operation.
- Hori, Hiroto,Arai, Shigeru,Nishida, Atsushi
-
supporting information
p. 4783 - 4788
(2019/05/24)
-
- Selective conversion of primary amides to esters promoted by KHSO4
-
Primary amides, either aliphatic or aromatic, are easily converted to the corresponding esters via reflux in lower primary alcohols in the presence of KHSO4. Secondary amides lead to complicated mixtures under analogous conditions, whereastertiary amides were inert. Use of isopropyl alcohol resulted inthe formation of product atslower rate and lower yieldalong withside products, whereas, use of tertiary alcoholsdid not give successful conversion andallyl and benzyl alcohol provided complex mixtures.
- Sattenapally, Narsimha,Sharma, Jhanvi,Hou, Yuqing
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p. 174 - 183
(2018/09/10)
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- METHOD OF PREPARING AZA-PYRIDONE COMPOUNDS
-
Disclosed herein are methods for obtaining aza-pyridone compounds, which can be useful for ameliorating and/or treating a disease and/or a condition, including an orthomyxovirus infection.
- -
-
Paragraph 0060; 0061
(2017/09/25)
-
- Iron-catalyzed arylation of α-aryl-α-diazoesters
-
An iron-catalyzed arylation of α-aryl-α-diazoesters with electron-rich benzene rings was developed, which provides an efficient method for the preparation of 1,1-diarylacetates with high yields and excellent chemo- and regio-selectivities.
- Yang, Ji-Min,Cai, Yan,Zhu, Shou-Fei,Zhou, Qi-Lin
-
supporting information
p. 5516 - 5519
(2016/07/06)
-
- Rh(I)-catalyzed cross-coupling of α-diazoesters with arylsiloxanes
-
An Rh(I)-catalyzed cross-coupling of diazoesters with arylsiloxanes has been successfully achieved. This transformation is a new method for the construction of the C(sp3)-C(sp2) bond, thus providing an alternative synthesis of α-aryl esters. Rh(I)-carbene migratory insertion has been proposed to be involved in this coupling reaction. The reaction represents the first example of utilizing arylsiloxane as the coupling partner in the carbene-involved cross-coupling reactions.
- Xia, Ying,Liu, Zhen,Feng, Sheng,Ye, Fei,Zhang, Yan,Wang, Jianbo
-
supporting information
p. 956 - 959
(2015/03/30)
-
- Rhodium catalyzed arylation of diazo compounds with aryl boronic acids
-
A general and efficient synthesis of diarylacetate, a diarylmethine derivative, was accomplished through rhodium catalyzed direct arylation of diazo compounds with arylboronic acids. The reaction tolerates various boronic acid derivatives and functional groups. Notably, chemoselective arylation of diazo compounds over other electrophiles were demonstrated. The efficacy of the developed methodology is shown by the expeditious synthesis of the core structure of diclofensine.
- Ghorai, Jayanta,Anbarasan, Pazhamalai
-
p. 3455 - 3461
(2015/04/14)
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- RhI-Catalyzed Stille-Type Coupling of Diazoesters with Aryl Trimethylstannanes
-
A RhI-catalyzed cross-coupling of diazoester with arylstannane was developed. This reaction represents the first Stille-type coupling that uses a diazo compound as the coupling partner. The reaction is operationally simple and can be carried out under mild conditions, thus providing an alternative approach for the synthesis of α-aryl esters. RhI-carbene migratory insertion process is suggested to be involved as the key step in this Stille-type coupling.
- Liu, Zhen,Xia, Ying,Feng, Sheng,Wang, Shuai,Qiu, Di,Zhang, Yan,Wang, Jianbo
-
p. 1379 - 1384
(2015/09/15)
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- 1,4-dihydropyridine-3,5-dicarboxylate Derivatives And Preparation And Use Thereof
-
The present invention relates to a 1,4-dihydropyridine-3,5-dicarboxylate compound of general compound (I), a process for preparing the same, a use thereof for the manufacture of a medicament for treating and/or preventing kidney injury, cardiovascular diseases and/or endocrine diseases, as well as a pharmaceutical composition and a pharmaceutical formulation containing said compounds, wherein the definitions of R1, R2, R3, R4, R5, R6, R7, R8, m, n1, n2, p and q are the same as those defined in the description.
- -
-
Paragraph 0159; 0160
(2014/03/21)
-
- 1,4-DIHYDROPYRIDINE -3,5-DICARBOXYLATE DERIVATIVES, PREPARATION METHODS AND USES THEREOF
-
The present invention relates to a 1,4-dihydropyridine-3,5-dicarboxylate compound of general compound (I), a process for preparing the same, a use thereof for the manufacture of a medicament for treating and/or preventing kidney injury, cardiovascular diseases and/or endocrine diseases, as well as a pharmaceutical composition and a pharmaceutical formulation containing said compounds, wherein the definitions of R1, R2, R3, R4, R5, R6, R7, R8, m, n1, n2, p and q are the same as those defined in the description.
- -
-
Paragraph 0143; 0144
(2014/03/25)
-
- First iodine-catalyzed deallylation of reactive allyl methylene esters
-
C-Allyl cleavage has been developed using the inexpensive and mild reagent iodine in dimethylsulfoxide. A variety of compounds with active methylene groups were C-deallylated using this reagent. This method is efficient and operationally simple in comparison to the methods using transition-metal complexes. Supplemental materials are available for this article. Go to the publisher's online edition of Synthetic Communications to view the free supplemental file.
- Nawghare, Beena R.,Lokhande, Pradeep D.
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p. 1955 - 1963
(2013/06/05)
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- Aluminum triflate as a powerful catalyst for direct amination of alcohols, including electron-withdrawing group-substituted benzhydrols
-
Direct aminations of allylic alcohols, benzylic alcohols, and benzhydrols with electron-withdrawing (F, Br, I, NO2, or CN) substituents were efficiently catalyzed by aluminum triflate [Al(OTf)3] to afford the corresponding biarylamines in high yield, and the dibromo-substituted product was further transformed into letrozole. Copyright
- Ohshima, Takashi,Ipposhi, Junji,Nakahara, Yasuhito,Shibuya, Ryozo,Mashima, Kazushi
-
supporting information
p. 2447 - 2452
(2012/11/07)
-
- Copper(I) enolate complexes in α-arylation reactions: Synthesis, reactivity, and mechanism
-
Copper is all bound up: The copper-catalyzed α-arylation of carbonyl compounds occurs through oxidative addition of iodoarenes to the C-bound Cu I enolate species 1 to form an aryl-CuIII intermediate (see scheme). Computational results provide insight into the origins of the relative reactivity of various CuI enolate complexes in the reactions with iodoarenes. Copyright
- Huang, Zheng,Hartwig, John F.
-
supporting information; experimental part
p. 1028 - 1032
(2012/03/09)
-
- Unusual behavior in the reactivity of 5-substituted- 1H-tetrazoles in a resistively heated microreactor
-
The decomposition of 5-benzhydryl-1H-tetrazole in an N-methyl-2- pyrrolidone/acetic acid/water mixture was investigated under a variety of high-temperature reaction conditions. Employing a sealed Pyrex glass vial and batch microwave conditions at 240 °, the tetrazole is comparatively stable and complete decomposition to diphenylmethane requires more than 8 h. Similar kinetic data were obtained in conductively heated flow devices with either stainless steel or Hastelloy coils in the same temperature region. In contrast, in a flow instrument that utilizes direct electric resistance heating of the reactor coil, tetrazole decomposition was dramatically accelerated with rate constants increased by two orders of magnitude. When 5-benzhydryl-1H-tetrazole was exposed to 220 ° in this type of flow reactor, decomposition to diphenylmethane was complete within 10 min. The mechanism and kinetic parameters of tetrazole decomposition under a variety of reaction conditions were investigated. A number of possible explanations for these highly unusual rate accelerations are presented. In addition, general aspects of reactor degradation, corrosion and contamination effects of importance to continuous flow chemistry are discussed.
- Gutmann, Bernhard,Glasnov, Toma N.,Razzaq, Tahseen,Goessler, Walter,Roberge, Dominique M.,Kappe, C. Oliver
-
supporting information; experimental part
p. 503 - 517
(2011/06/28)
-
- Carbon-carbon bond-forming reactions of α-carbonyl carbocations: Exploration of a reversed-polarity equivalent of enolate chemistry
-
Carbon-carbon bond-forming reactions of putative α-carbonyl carbocation intermediates generated by Lewis acid- or silver-promoted ionizations of toluenesulfonate or halide leaving groups are described. This under-exploited mode of reactivity represents an 'umpolung' of conventional enolate chemistry, and enables C-C bond construction in both intra- and intermolecular contexts. Attempts to develop diastereoselective variants of this process using chiral ester and oxazolidinone-based auxiliaries are discussed.
- Lai, Ping-Shan,Dubland, Joshua A.,Sarwar, Mohammed G.,Chudzinski, Michael G.,Taylor, Mark S.
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p. 7586 - 7592
(2011/10/12)
-
- PDE10 INHIBITORS AND RELATED COMPOSITIONS AND METHODS
-
Compounds that inhibit PDE10 are disclosed that have utility in the treatment of a variety of conditions, including (but not limited to) psychotic, anxiety, movement disorders and/or neurological disorders such as Parkinson's disease, Huntington's disease, Alzheimer's disease, encephalitis, phobias, epilepsy, aphasia, Bell's palsy, cerebral palsy, sleep disorders, pain, Tourette's syndrome, schizophrenia, delusional disorders, drug-induced psychosis and panic and obsessive-compulsive disorders. Pharmaceutically acceptable salts, stereoisomers, solvates and prodrugs of the compounds are also provided. Also disclosed are compositions containing a compound in combination with a pharmaceutically acceptable carrier, as well as methods relating to the use thereof for inhibiting PDE10 in a warm-blooded animal in need of the same.
- -
-
Page/Page column 11
(2010/03/02)
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- Chemoselective esterification and amidation of carboxylic acids with imidazole carbamates and ureas
-
Imidazole carbamates and ureas were found to be chemoselective esterification and amidation reagents. A wide variety of carboxylic acids were converted to their ester or amide analogues by a simple synthetic procedure in high yields.
- Heller, Stephen T.,Sarpong, Richmond
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supporting information; experimental part
p. 4572 - 4575
(2010/12/25)
-
- A Simple, efficient, green, cost effective and chemoselective process for the esterification of carboxylic acids
-
Carboxylic acids have been esterified under mild and solvent-free conditions in high yield and purity using the green reagents, dimethyl carbonate and diethyl carbonate, under acid catalysis. The present methodology is free of the disadvantages of base catalysis described earlier, such as high temperatures, use of autoclaves, use of the expensive DBU as base in stoichiometric amounts and the carbonate as solvent. High chemoselectivity is observed in the case of hydroxybenzoic acids.
- Rekha,Ramani, Modukuri V.,Ratnamala,Rupakalpana, Vempati,Subbaraju, Gottumukkala V.,Satyanarayana, Chava,Rao, C. Someswara
-
experimental part
p. 769 - 773
(2010/04/22)
-
- Arylation and vinylation of α-diazocarbonyl compounds with boroxines
-
An alternative approach for α-arylation and α-vinylation of carbonyl compounds is described: reaction between aryl-or vinylboroxines with α-diazocarbonyl compounds leads to the formation of α-arylated or α-vinylated carbonyl compounds under mild conditions.
- Peng, Cheng,Zhang, Wei,Yan, Guobing,Wang, Jianbo
-
supporting information; experimental part
p. 1667 - 1670
(2009/08/07)
-
- A novel synthetic route to 2-arylalkanoic acids by a ruthenium-catalyzed chemoselective oxidation of furan rings
-
An efficient two-step synthesis of 2-arylalkanoic acids from 1-arylalkanols is described. Firstly, 1-arylalkylfuran derivatives were synthesized in high yields by the metal triflate catalyzed Friedel-Crafts alkylation of 2-methylfuran with 1-arylalkanols without employing anhydrous conditions. The chemoselective oxidation of the furan ring in 1-arylalkylfurans to carboxylic acid was then investigated. In a solvent system of hexane-EtOAc/H2O (1:3:4), the furan ring was selectively oxidized with 7 equivalents of NaIO 4 by using 0.5 mol% RuCl3 as catalyst to give 2-arylalkanoic acids in good yields. The selectivity of ruthenium oxidation was controlled by the solvent ratio of hexane-EtOAc. Georg Thieme Verlag Stuttgart.
- Noji, Masahiro,Sunahara, Haruka,Tsuchiya, Ken-Ichi,Mukai, Toru,Komasaka, Ayako,Ishii, Keitaro
-
experimental part
p. 3835 - 3845
(2009/07/04)
-
- Effective esterification of carboxylic acids using (6-oxo-6H-pyridazin-1-yl)phosphoric acid diethyl ester as novel coupling agents
-
(6-Oxo-6H-pyridazin-1-yl)phosphoric acid diethyl esters (3) are efficient and selective coupling agents for equimolar esterification of carboxylic acids and alcohols. Esterification of aliphatic and aromatic carboxylic acids with aliphatic and aromatic alcohols using 3 afforded the corresponding esters chemoselectively in good to excellent yield.
- Won, Ju-Eun,Kim, Ho-Kyun,Kim, Jeum-Jong,Yim, Heong-Seup,Kim, Min-Jung,Kang, Seung-Beom,Chung, Hyun-A.,Lee, Sang-Gyeong,Yoon, Yong-Jin
-
p. 12720 - 12730
(2008/03/14)
-
- New 1,3-dioxolane and 1,3-dioxane derivatives as effective modulators to overcome multidrug resistance
-
Multidrug resistance (MDR) to antitumor agents represents a major obstacle to a successful chemotherapy of cancer. Overexpression of P-glycoprotein (p-gp) seems to be the major factor responsible for MDR. A large number of chemically unrelated compounds are known to interact with p-gp resulting in a decreasing resistance. In our efforts related to structure-activity studies of new potential MDR reversal agents we synthesized a series of compounds that differ in the aromatic core structure, the linker, and the basic moiety. For our search of new aromatic core structures we synthesized novel 2,2-diphenyl-1,3-dioxolane, 2,2- diphenyl-1,3-dioxane, and 4,5-diphenyl-1,3-dioxolane derivatives. A range of lipophilic linker structures and protonable basic moieties were synthesized and investigated to optimize the structure of the potential MDR-modulators. The compounds were tested in vitro using human Caco-2 cells. Both the cytotoxicity of the synthons and their ability to resensitize the cells were determined with a MTT assay. The results show that at low concentration various substances reverse tumor cell MDR. Some of the new structures show better effects than established modulators like trifluoperazine.
- Schmidt, Matthias,Ungvari, Johannes,Gloede, Julia,Dobner, Bodo,Langner, Andreas
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p. 2283 - 2297
(2007/10/03)
-
- Identification of a potent botulinum neurotoxin A protease inhibitor using in situ lead identification chemistry
-
Botulinum neurotoxins (BoNTs), etiological agents of the deadly food poisoning disease botulism, are the most toxic proteins currently known. By using in situ lead identification chemistry, we have uncovered the first class of inhibitors that displays nanomolar potency. From a 15 μM lead compound, structure-activity relationship studies were performed granting the most potent BoNT/A inhibitor reported to date that displays an inhibition constant of 300 nM.
- Boldt, Grant E.,Kennedy, Jack P.,Janda, Kim D.
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p. 1729 - 1732
(2007/10/03)
-
- Facile and catalytic degradation method of DDT using Pd/C-Et3N system under ambient pressure and temperature
-
The catalytic degradation method of p,p′-DDT [1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane] and its regioisomer o,p′-DDT [1,1,1-trichloro-2-(o-chlorophenyl)-2-(p-chlorophenyl)ethane] using the Pd/C-Et3N system under ambient hydrogen pressure and temperature was established. The presence of Et3N was necessary for the quick and complete breakdown of DDT. The independent degradation study of two intermediates, p,p′-DDD [2,2-bis(p-chlorophenyl)-1,1-dichloroethane] and p,p′-DDE [2,2-bis(p-chlorophenyl)-1,1-dichloroethylene] using GC-MS let us to speculate the degradation pathway of p,p′-DDT. In the initial phase of the reaction, p,p′-DDT degradation splits into two ways: a dehydrochlorination pathway and a hydrodechlorination pathway. In each pathway, reaction starts from an aliphatic moiety and subsequent hydrodechlorination from the benzene moieties takes place in a stepwise manner. The former pathway leads to the formation of 1,1-diphenylethane and the latter leads to the formation of 1,1-dichloro-2,2-diphenylethane. These diphenylethane analogs, which are less toxic compared with p,p′-DDT, are terminal degradation products in our system. The distinctive features of our catalytic degradation method of DDTs are reliability, simplicity, efficiency, and inexpensiveness.
- Monguchi, Yasunari,Kume, Akira,Sajiki, Hironao
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p. 8384 - 8392
(2007/10/03)
-
- Polymer-supported triazenes as smart reagents for the alkylation of carboxylic acids
-
Starting from polystyrene, a simple four-step synthesis of polymer-supported alkyltriazenes (alkyl = Me, Et, benzyl) is described. With this synthesis, a loading capacity of 2.2 mmol g-1 can be reached. The most prominent application of these polymer-supported reagents is the rapid, highly selective and high-yielding esterification of carboxylic acids, which involves a simple mix and filter off procedure at room temperature. If stored in a refrigerator, these reagents are stable for many months and they can be recycled several times.
- Erb, Bernhard,Kucma, Jean-Philippe,Mourey, Sandrine,Struber, Fritz
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p. 2582 - 2588
(2007/10/03)
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- Anodic oxidation of benzil hydrazones in the presence of halide ions
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Benzil hydrazones were subjected to electrolytic oxidation in MeOH containing halide ion source, such as KI and KBr. The results show that the reaction products were dependent on both the electrolytes and the substituents. In the presence of KI, benzoylphenyldiazomethanes were obtained, whereas in the presence of KBr, benzil dimethyl acetals were obtained.
- Okimoto, Mitsuhiro,Takahashi, Yukio
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p. 2059 - 2060
(2007/10/03)
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- Synthesis and antitumour activity of new derivatives of flavone-8-acetic acid (FAA). Part 4: Variation of the basic structure
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A range of 11 derivatives of flavone-8-acetic acid (FAA) in which the structure has been substantially altered in different ways have been prepared and their anti-tumour activity evaluated in vitro against a panel of human and murine tumour cell lines and in vivo against MAC 15A. The generally poor activity observed shows that the basic structure cannot be altered much without destroying the activity.
- Alan Aitken,Bibby, Michael C.,Cooper, Patricia A.,Double, John A.,Laws, Andrea L.,Ritchie, Robert B.,Wilson, David W.J.
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p. 181 - 188
(2007/10/03)
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- Intermolecular cyclopropanation versus CH insertion in Rh(II)-catalyzed carbenoid reactions
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The product ratio of intermolecular insertion and cyclopropanation in transition metal-catalyzed diazo decompositions depends strongly upon the metal, its ligands and upon the substituents of the diazo compound. Ethyl diazoacetate (2a) reacts with cyclohexene (1) almost exclusively by cyclopropanation. However, diazomalonate (2d) and methyl 2-diazophenylacetate (2e) in the presence of Rh(II) catalysts exhibit a marked tendency towards allylic CH insertion. With 1,4-cyclohexadiene (6), methyl 2- diazophenylacetate (2e) in the presence of chiral Rh(II) catalysts affords the allylic insertion product 7 in almost quantitative yield and with up to 74% ee. (C) 2000 Elsevier Science Ltd.
- Müller, Paul,Tohill, Sarah
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p. 1725 - 1731
(2007/10/03)
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- Generation of ketenes by photolysis of naphtho[1,8-de]-1,3- dichalcogeninylidene 1-oxides
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The photolysis of naphtho[1,8-de]-1,3-dichalcogeninylidene 1-oxide derivatives (4 and 5) at >290 nm generates ketenes together with naphtho[1,8- cd]-1,2-dichalcogenole, which were confirmed by the trapping experiments and the direct observation using IR spectroscopy. The generation of ketenes from the selenium compounds 5 is more effective than that from the sulfur analogs 4.
- Kobayashi, Kenji,Shinhara, Satoshi,Moriyama, Masaya,Fujii, Takayoshi,Horn, Ernst,Yabe, Akira,Furukawa, Naomichi
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p. 5211 - 5214
(2007/10/03)
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- Regioselective Arylation Reactions of Biphenyl-2-ols, Naphthols, and Benzylic Compounds with Aryl Halides under Palladium Catalysis
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Biphenyl-2-ols undergo regioselective mono- and diarylation upon a treatment with aryl iodides in the presence of a palladium catalyst in DMF using Cs2CO3 as a base to produce 1,1′ : 2′,1″-terphenyl-2-ol and 2′,6′-diphenylbiphenyl-2-ol and their derivatives. The reaction of 1-naphthol selectively occurs at its 8-position to give 8-aryl-1-naphthols. In the reaction of 2-naphthol with aryl bromides, diarylated compounds, 1-(2-arylphenyl)-2-naphthols, are formed as the single major products. Under similar conditions, benzyl ketones, phenylacetonitrile, and methyl phenylacetate are arylated at their benzylic position.
- Satoh, Tetsuya,Inoh, Jun-Ichi,Kawamura, Yoshiki,Kawamura, Yuichiro,Miura, Masahiro,Nomura, Masakatsu
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p. 2239 - 2246
(2007/10/03)
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- Reaction of Silyl Enol Ethers with Arenediazonium Salts. Part 2. α-Amination of Esters
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Diazonium salts efficiently serve as electrophilic aminating reagents of esters.The reaction of arenediazonium tetrafluoroborates with ketene silyl ketals yielded α-azo or α-hydrazono esters in good to excellent yields under very mild conditions.Hydrogenation of those esters gave α-amino esters quantitatively.
- Sakakura, Toshiyasu,Hara, Masayasu,Tanaka, Masato
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p. 289 - 294
(2007/10/02)
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- The photochemistry of mixed anhydrides: A search for selectivity in photochemically initiated bond cleavage reactions
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A number of mixed anhydrides (RC(O)OC(O)R') have been synthesized for the purpose of exploring the regioselectivity of their photochemical reactions. The photochemical reaction products, quantum yields, and reaction rates have been determined. For those compounds containing no α-hydrogens, high regioselectivity is obtained upon irradiation and can be understood on the basis of the relative C-O bond dissociation energies. The reaction can be quenched by intramolecular electron transfer. For those compounds containing α-hydrogen atoms, the Norrish type II reaction is faster than the corresponding C-O cleavage reactions, resulting in poor regioselectivity.
- Penn, John H.,Owens, Walter H.
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- Nucleophilic substitution in diphenylmethyl derivatives. II. Methanolysis of α substituents of diphenylacetic acid and its derivatives
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The nucleophilic displacement of α substituents of diphenylacetic acid and its methyl ester by MeOH under a variety of experimental conditions allowed us to establish that the reaction occurs rapidly in one of the following structural combinations: (a) carboxylate anion and a good leaving group; (b) carboxylic group and a less reactive leaving group; (c) methyl ester and a proton-activated, poor leaving group.The importance of internal hydrogen bonding (case b) was the governing factor in the outcome of the reaction of hydroxydiphenylacetic acid (3a) and its methyl ester 3b with acetyl chloride.The key intermediate in substitution at the α carbon is thought to be a carbocation stabilized both by the attached phenyl groups and, to a smaller extent, by the carboxyl group.
- Strazzolini, Paolo,Poiana, Marco,Verardo, Giancarlo,Giumanini, Angelo G.
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p. 283 - 289
(2007/10/02)
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- Reduction of Long Chain and Bulky Carboxylic Esters by Sodium Tetrahydroborate
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Methyl esters of long chain fatty acids as well as esters with functional (OH) and/or bulky substituents in alpha position and in the OR moiety may be effectively reduced with an excess of sodium tetrahydroborate at moderate temperature in dioxane-water without catalysts.The reaction has been applied to the reduction of a pool of triglycerides of natural origin (virgin olive oil) in order to obtain a mixture of the acyl residues reduced to the corresponding alcohols without any structural or configurational modification.They, no matter which was the advancement of the reaction, seemed to reproduce quite well the overall acyl composition, as shown by GC-MS analysis: the feasibility of such quantitative analysis may be extended, in order to obtain confirmatory evidences on the component identifications and to perform specific separations, to the corresponding chlorides, hydrocarbons and trimethylsilylethers.
- Giumanini, Angelo G.,Tubaro, Franco
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p. 755 - 761
(2007/10/02)
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- Pentaalkylguanidines as etherification and esterification catalysts
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Several pentaalkylguanidines have been prepared and found to be superior catalysts for the preparation of aryl and aralkyl ethers from carbonates and for the methylation of phenols with dimethylcarbonate.They also act as effective catalysts for esterification of acids with alkyl chloroformates but not for the acetylation of tertiary alcohols with acetic anhydride.
- Barcelo, Gerard,Grenouillat, Denis,Senet, Jean-Pierre,Sennyey, Gerard
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p. 1839 - 1848
(2007/10/02)
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- Y-Conjugated Dianions. A 13C Nuclear Magnetic Resonance Study
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Tris(diphenylmethylene)methane dianion (12-), tetraphenylacetone dianion (22-), and diphenylacetate dianion (32-) were generated in dimethyl sulfoxide or tetrahydrofuran solutions by deprotonation of the appropriate carbon acid.Chemical shifts, carbon-carbon spin coupling constants, and other spectroscopic evidence indicated an sp2-hybridized central atom for all dianions, as well as D3 symmetry for the all-carbon dianion.The one-bond CC spin coupling constant for 12- (62 Hz) increased upon consecutive replacements of diphenylmethylene by the groups, i.e., to 69 Hz for 22- and 76.7 Hz for 32-,2K+ (86.0 Hz for the Li+ salt) reflecting charge localization at oxygen.An empirical model for the residual charge on phenyl-substituted resonance-stabilized carbanions that allows comparison of dissimilarly substituted carbanions was developed.
- Rajca, Andrzej,Tolbert, Laren M.
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p. 871 - 876
(2007/10/02)
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- Biotransformation of denaverine hydrochloride (Spasmalgan) in the rat
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After oral application of denaverine hydrochloride to rats (200-250 mg/kg) 12 metabolites have been detected in urine.Besides the unchanged drug, 8 metabolites were identified by MS as 2,2-diphenyl-(2-dimethylaminoethyl)acetate (3), diphenylacetic (5) and benzilic acid (6), methyl- and ethyl acetate (7,11), methylbenzilate (10),N-demethyl-1 (12) and 3,3-diphenylmorpholin-2-one (13). 6 and metabonate 13 represent the main metabolic products.Compounds 7 and 11 indicate the metabolic pathway about an alkoxybenzilic acid (4).Phenols resp. conjugates were not detected.
- Goeber, B.,Lisowski, Hannelore,Friese, Dagmar,Franke, P.
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p. 493 - 495
(2007/10/02)
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- α-HYDROXYLATION OF CARBOXYLIC ACIDS AND AMIDES USING BIS(TRIMETHYLSILYL)PEROXIDE
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Bis(trimethylsilyl)peroxide is shown to react with enolate anions derived from carboxylic acids and amides to give the corresponding α-hydroxy derivatives.
- Pohmakotr, Manat,Winotai, Chanchai
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p. 2141 - 2146
(2007/10/02)
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