- Direct and Selective Synthesis of Adipic and Other Dicarboxylic Acids by Palladium-Catalyzed Carbonylation of Allylic Alcohols
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A general and direct synthesis of dicarboxylic acids including industrially important adipic acid by palladium-catalyzed dicarbonylation of allylic alcohol is reported. Specifically, the combination of PdCl2 and a bisphosphine ligand (HeMaRaphos) promotes two different carbonylation reactions with high activity and excellent selectivity.
- Beller, Matthias,Ge, Yao,Huang, Weiheng,Jackstell, Ralf,Liu, Jiawang,Neumann, Helfried,Yang, Ji
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supporting information
p. 20394 - 20398
(2020/09/21)
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- Regioselective Isomerization of Terminal Alkenes Catalyzed by a PC(sp3)Pincer Complex with a Hemilabile Pendant Arm
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We describe an efficient protocol for the regioselective isomerization of terminal alkenes employing a previously described bifunctional Ir-based PC(sp3)complex (4) possessing a hemilabile sidearm. The isomerization, catalyzed by 4, results in a one-step shift of the double bond in good to excellent selectivity, and good yield. Our mechanistic studies revealed that the reaction is driven by the stepwise migratory insertion of Ir?H species into the terminal double bond/β-H elimination events. However, the selectivity of the reaction is controlled by dissociation of the hemilabile sidearm, which acts as a selector, favoring less sterically hindered substrates such as terminal alkenes; importantly, it prevents recombination and further isomerization of the internal ones.
- De-Botton, Sophie,Filippov, D.Sc. Oleg A.,Shubina, Elena S.,Belkova, Natalia V.,Gelman, Dmitri
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p. 5959 - 5965
(2020/10/15)
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- Palladium catalyzed carbonylations of alkenyl halides with formic acid to get corresponding Α,Β-unsaturated carboxylic acids and esters
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Palladium-catalysed carbonylation reactions have been developed in the presence of formic acid as carbon monoxide source. α,β-Unsaturated carboxylic acids and esters were synthesized by the transformation of alkenyl halides in moderate to good yields. The selection of the base proved to be crucial regarding the reaction outcome. A set of various substrates were proven under optimised reaction conditions. Compared to aliphatic alcohols, phenols showed excellent reactivity as O-nucleophiles.
- Bartal, Brigitta,Mikle, Gábor,Kollár, László,Pongrácz, Péter
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p. 143 - 149
(2019/02/15)
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- Lithium perchlorate catalyzed electrophilic activation: A convenient one-pot synthesis of trans-cinnamic acids
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Background: Currently perchlorate catalysts gain much attention in organic synthesis due to ease of operation, wide applicability, high yield, and economy. This is evident through increasing number of citation related to their application in industry as well as other allied fields. The aim of this paper is to describe a methodology using lithium perchlorate to catalyze the Knoevenagel condensation reaction for the synthesis of biologically active trans-cinnamic acid in good to excellent yield. Methods: We discuss herein an economic, user-friendly one-pot synthesis of trans-cinnamic acids by refluxing a mixture of a malonic acid with aryl aldehyde in pyridine. The product was easily isolated via filtration and thereafter washed and characterized by spectroscopic methods. Results: This method is robust, stereoselective and high yielding. It can be utilized to synthesize a wide array of trans-cinnamic acids in good to excellent yield using 20% of lithium perchlorate catalyst. It is also useful in the synthesis of aliphatic α,β-unsaturated carboxylic acid. Conclusion: The role of lithium perchlorate as a mild catalyst in the synthesis of trans-cinnamic acid was explored. The reactions afforded a good yield of various products with simpler isolation.
- Kaur, Paranjeet,Khatik, Gopal L.
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p. 688 - 692
(2018/07/13)
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- Selective Isomerization of Terminal Alkenes to (Z)-2-Alkenes Catalyzed by an Air-Stable Molybdenum(0) Complex
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Positional and stereochemical selectivity in the isomerization of terminal alkenes to internal alkenes is observed using the cis-Mo(CO)4(PPh3)2 precatalyst. A p-toluenesulfonic acid (TsOH) cocatalyst is essential for catalyst activity. Various functionalized terminal alkenes have been converted to the corresponding 2-alkenes, generally favoring the Z isomer with selectivity as high as 8:1 Z:E at high conversion. Interrogation of the catalyst initiation mechanism by 31P NMR reveals that cis-Mo(CO)4(PPh3)2 reacts with TsOH at elevated temperatures to yield a phosphine-ligated Mo hydride (MoH) species. Catalysis may proceed via 2,1-insertion of a terminal alkene into a MoH group and stereoselective β-hydride elimination to yield the (Z)-2-alkene.
- Becica, Joseph,Glaze, Owen D.,Wozniak, Derek I.,Dobereiner, Graham E.
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p. 482 - 490
(2018/02/17)
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- A CATALYST FOR THE CARBONYLATION OF ALKENES
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The present application relates to a metal complex of Formula (I) and a catalyst composition for the carbonylation of alkenes comprising the metal complex, wherein the metal is a group 10 element such as palladium, platinum or nickel, and the complex comprises a bidentate phosphine ligand. The present invention also relates to a process for the preparation of a dicarboxylic acid or ester thereof from an alkenoic acid or ester thereof, or a process for the preparation of a carboxylic acid or ester thereof from an alkene or alkenoic acid with high selectivity and activity using said metal complex or catalyst composition. The present application also relates to a method of preparing Nylon 6-6 comprising the step of copolymerising adipic acid with hexamethylenediamine.
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Page/Page column 44
(2017/09/02)
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- PROCESS FOR PREPARING MONO AND DICARBOXYLIC ACIDS
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The present application relates to a process for preparing a dicarboxylic acid or dicarboxylic ester according to general formula (IV) R1OOC-(CH2)m-CH2CH2-(CH2)y-COOR4 (IV), comprising the steps of subjecting alkenoic acid or alkenoate of formula (II) R1OOC-(CH2)m-CH=CH-(CH2)x-H (II) to a metathesis reaction in the presence of a metathesis catalyst to form a longer-chain alkenoic acid or alkenoate of formula (III) R1OOC-(CH2)m-CH=CH-(CH2)y-H (III) where xa carbonylation reaction in the presence of a carbonylation catalyst and a carbonyl source to form said compound of Formula (IV). Alternative embodiments provide: a process for preparing an alkenoic acid or alkenoate comprising the step of subjecting a lactone to a ring opening reaction; a process for preparing a monocarboxylic acid or monocarboxylic ester according to general formula (XI) R1OOC-(CH2)m-CH2-(CH2)y-CH3 (XI) by subjecting an alkenoic acid or alkenoate to alkene hydrogenation; and a process for preparing an alcohol or ether according to general formula (XII) R1O-CH2-(CH2)m-CH2-(CH2)y-CH3 (XII) by subjecting an alkenoic acid or alkenoate to hydrogenation. The use of the respective mono/dicarboxylic acid, mono/dicarboxylic ester, ethers or alcohols in a variety of applications is also disclosed.
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Page/Page column 33
(2018/02/03)
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- MANUFACTURING METHOD OF α,β-UNSATURATED CARBOXYLIC ACID
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PROBLEM TO BE SOLVED: To provide a manufacturing method which can get α,β-unsaturated carboxylic acid at a high yield by liquid phase oxidation of α,β-unsaturated aldehyde by oxygen or air with a handy metal catalyst under a mild reaction condition. SOLUTION: Preferably under a presence of organic solvent, α,β-unsaturated carboxylic acid is manufactured by oxidation of α,β-unsaturated aldehydes and oxygen or air under a presence of an iron salt catalyst and a catalyst of alkali metal salt of carboxylic acid. SELECTED DRAWING: None COPYRIGHT: (C)2017,JPOandINPIT
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Paragraph 0050-0052
(2018/10/16)
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- Iron-catalyzed selective oxidation of α,β-unsaturated aldehydes to α,β-unsaturated carboxylic acids by molecular oxygen
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Selective oxidation of α,β-unsaturated aldehydes to α,β-unsaturated carboxylic acids was performed using O2 as the oxidant in the presence of a simple iron catalyst. The addition of an alkali metal carboxylate as a cocatalyst enhanced the selectivity for the desired product. Redox tuning of the iron catalyst via association with the alkali metal led to a controlled radical generation during the catalytic O2 oxidation.
- Tanaka, Shinji,Kon, Yoshihiro,Uesaka, Yumiko,Morioka, Ryo,Tamura, Masanori,Sato, Kazuhiko
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supporting information
p. 188 - 190
(2016/03/01)
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- Preparation and odour of cis- and trans-2-methyltetrahydrofuran-3-thiol acetates
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The preparation of cis- and trans-2-methyltetrahydrofuran-3-thiol acetates from (E)-3-penten-1-ol is reported. The mesylate of (E)-3-penten-1-ol was converted into trans- or cis-2-methyl-3-hydroxytetrahydrofuran by oxidation with H2O2 and HCOOH or with KMnO4. cis- or trans-2-Methyltetrahydrofuran-3-thiol acetate was prepared by mesylation and an SN2 nucleophilic substitution with AcSH from trans- or cis-2-methyl-3-hydroxytetrahydrofuran respectively. The configuration of the products was confirmed by their synthesis. Olfactory evaluation of cis- and trans-2-methyltetrahydrofuran-3-thiol acetates indicated some differences both in odour feature and intensity.
- Dai, Yifeng,Sun, Baoguo,Yang, Shaoxiang,Liu, Yongguo,Tian, Hongyu,Shao, Junqiang
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p. 236 - 239
(2014/05/06)
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- A PROCESS TO PRODUCE A DIENE FROM A LACTONE
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The invention provides a process for the production of a diene. In the process, a lactone is heated in the presence of a first catalyst system to produce an alkene and carbon dioxide and the alkene is contacted with a second catalyst system to produce an alkyldiene.
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Page/Page column 27; 28
(2013/10/21)
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- Method for regio- and stereoselective synthesis of (E)-Β,γ- unsaturated acids from aldehydes under solvent-free conditions
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Synthesis of (E)-β,-γunsaturated acids from aldehydes with malonic acid has been explored under solvent-free conditions. The modified Knoevenagel condensation reaction with N-methyl morpholine (NMM) as catalyst exhibits highly β,-γ regioselectivity and exclusively E-stereoselectivity. A mechanism accounting for both regio- and stereoselectivity has been proposed and preliminarily studied. Copyright Taylor & Francis Group, LLC.
- Zhang, Shi-Jie,Hu, Wei-Xiao
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experimental part
p. 3093 - 3100
(2010/12/19)
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- Anticancer platinum complexes as non-innocent compounds for catalysis in aqueous media
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An efficient cyclization of alkyne-acids to enol-lactones catalyzed by anticancer platinum(ii) and platinum(iv) compounds is described. These compounds are not only DNA-binding complexes; they can also catalyze reactions in solvents such as acetone, methanol, water or blood plasma.
- Aleman, Jose,Del Solar, Virginia,Navarro-Ranninger, Carmen
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supporting information; experimental part
p. 454 - 456
(2010/04/30)
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- New reactions of anticancer-platinum complexes and their intriguing behaviour under various experimental conditions
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The anticancer platinum complexes here described react with organic substrates (such as acids, alkenes, alkynes) and catalyze transformations that can occur in biomolecules which contain unsaturated functions. We have analyzed the role of the platinum complexes in the observed reactions and studied the progress of the detected transformations upon variation of the reaction conditions. The Royal Society of Chemistry 2010.
- Aleman, Jose,Del Solar, Virginia,Cubo, Leticia,Quiroga, Adoracion G.,Navarro Ranninger, Carmen
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scheme or table
p. 10601 - 10607
(2011/01/05)
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- Catalytic Conversion of Cellulose to Liquid Hydrocarbon Fuels by Progressive Removal of Oxygen to Facilitate Separation Processes and Achieve High Selectivities
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Described is a method to make liquid chemicals, such as functional intermediates, solvents, and liquid fuels from biomass-derived cellulose. The method is cascading; the product stream from an upstream reaction can be used as the feedstock in the next downstream reaction. The method includes the steps of deconstructing cellulose to yield a product mixture comprising levulinic acid and formic acid, converting the levulinic acid to γ-valerolactone, and converting the γ-valerolactone to pentanoic acid. Alternatively, the γ-valerolactone can be converted to a mixture of n-butenes. The pentanoic acid so formed can be further reacted to yield a host of valuable products. For example, the pentanoic acid can be decarboxylated yield 1-butene or ketonized to yield 5-nonanone. The 5-nonanone can be hydrodeoxygenated to yield nonane, or 5-nonanone can be reduced to yield 5-nonanol. The 5-nonanol can be dehydrated to yield nonene, which can be dimerized to yield a mixture of C9 and C18 olefins, which can be hydrogenated to yield a mixture of alkanes. Alternatively, the nonene may be isomerized to yield a mixture of branched olefins, which can be hydrogenated to yield a mixture of branched alkanes. The mixture of n-butenes formed from γ-valerolactone can also be subjected to isomerization and oligomerization to yield olefins in the gasoline, jet and Diesel fuel ranges.
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Page/Page column 10-11
(2010/12/31)
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- Catalytic aerobic oxidation of allylic alcohols to carbonyl compounds under mild conditions
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A new catalytic aerobic oxidation of alcohols to aldehydes under green conditions was developed (room temperature and pressure, water solution, open vials). The water-soluble platinum(II) tetrasulfophthalocyanine (PtPcS) catalyst showed the best selectivity for carbonyl derivatives, and in particular for α,β-unsaturated alcohols; the reactions are slow.
- Tonucci, Lucia,Nicastro, Marco,D'Alessandro, Nicola,Bressan, Mario,D'Ambrosio, Primiano,Morvillo, Antonino
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experimental part
p. 816 - 820
(2010/04/23)
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- Organocatalysis in conjugate amine additions. Synthesis of β-amino acid derivatives
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Conjugate addition of O-protected hydroxylamines to pyrazole-derived enoates proceeds with high efficiency and enantioselectivity when chiral thioureas are used as activators. A wide variety of substrates undergo conjugate amine addition providing access to enantioenriched β-amino acid derivatives. Structural requirements for the optimal thiourea catalyst have been established, and the results suggest that it operates as a bifunctional catalyst. Copyright
- Sibi, Mukund P.,Itoh, Kennosuke
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p. 8064 - 8065
(2008/02/09)
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- PROCESS FOR THE CARBONYLATION OF A CONJUGATED DIENE
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A process for the carbonylation of a conjugated diene, comprising reacting the conjugated diene with carbon monoxide and a co-reactant having a mobile hydrogen atom in the presence of a catalyst system including: (a) a source of palladium; and (b) a bidentate diphosphine ligand of formula (II): R1R2 > p1R3m-R-R4n-p2 5R6 wherein p1 and p2 represent phosphorus atoms; R1, R2, R5, and R6 independently represent the same or different optionally substituted organic radical containing a tertiary carbon atom through which each radical is linked to the phosphorus atom; R3 and R4 independently represent the same or different optionally substituted methylene groups; R represents an organic group comprising the bivalent bridging group C1-C2 through which R is connected to R3 and R4; m and n independently represent a natural number in the range of from 0 to 4, wherein the rotation about the bond between the carbon atoms C1 and C2 of the bridging group is restricted a temperature in the range of from 0 °C to 250 °C, and wherein the dihedral angle between the plane occupied by the three atom sequence composed of C1, C2 and the atom directly bonded to C1 in the direction of p1, and the plane occupied by the three atom sequence C1, C2 and the atom directly bonded to C2 in the direction of p2, is in the range of from 0 to 120°; and (c) a source of an anion.
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- PREPARATION OF (E)- AND (Z)-2-METHYL-2-BUTENOIC ACIDS
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A method has been developed to prepare (E)- and (Z)-2-methyl-2-butenoic acids (2M2BA) from a mixture of (E,Z)-2-methyl-2-butenenitriles (2M2BN) by the regioselective hydrolysis of (E)-2M2BN to (E)-2-methyl-2-butenoic acid (2M2BA) using enzyme catalysts having either a nitrilase activity or a combination of nitrile hydratase and amidase activities. The method provides high yields without significant conversion of (Z)-2M2BN to (Z)-2M2BA. The regioselective hydrolysis of (E)-2M2BN to (E)-2M2BA makes possible the facile separation of (E)-2M2BA from (Z)-2M2BN or (Z)-2-methyl-2-butenamide (2M2BAm), and the subsequent conversion of (Z)-2M2BN or (Z)-2M2BAm to (Z)-2M2BA.
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- Regioselective biocatalytic hydrolysis of (E,Z)-2-methyl-2-butenenitrile for production of (E)-2-methyl-2-butenoic acid
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Acidovorax facilis 72W nitrilase catalyzed the regioselective hydrolysis of (E,Z)-2-methyl-2-butenenitrile, producing only (E)-2-methyl-2-butenoic acid with no detectable conversion of (Z)-2-methyl-2-butenenitrile. (E)-2-Methyl-2-butenoic acid, produced in aqueous solution as the ammonium salt, was readily separated from (Z)-2-methyl-2-butenenitrile, and isolated in high yield and purity. The combination of nitrile hydratase and amidase activities of several Comamonas testosteroni strains were also highly regioselective for the production of (E)-2-methyl-2-butenoic acid from (E,Z)-2-methyl-2- butenenitrile.
- Hann, Eugenia C.,Sigmund, Amy E.,Fager, Susan K.,Cooling, Frederick B.,Gavagan, John E.,Bramucci, Michael G.,Chauhan, Sarita,Payne, Mark S.,DiCosimo, Robert
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p. 577 - 581
(2007/10/03)
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- Alkylation of lithium dienediolates of butenoic acids. Regioselectivity effects of structure and leaving group of the alkylating agent
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Regioselectivity of alkylation of but-2-enoic acids I and 2 by alkyl halides strongly depends on the reactivity of the electrophile. High α selectivity results for saturated alkyl halides, whereas poor α-selectivity is obtained for highly reactive allyl and benzyl halides. For reactive alkylating halides selectivity is partly governed by the ion pairing aggregates of the dienediolates. Lithium bromide and the carboxylate generated in the ongoing reaction cause opposite effects on regioselectivity.
- Aurell, Maria J.,Gil, Salvador,Mestres, Ramon,Parra, Margarita,Parra, Lilian
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p. 4357 - 4366
(2007/10/03)
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- Two-carbon homologation of aldehydes via silyl ketene acetals: A new stereoselective approach to (E)-alkenoic acids
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Aldehydes are converted into (E)-α,β-unsaturated carboxylic acids using C,O,O-tris(trimethylsilyl)ketene acetal 1. This organosilicon reagent is easily generated from trimethylsilyl acetate, LDA, and chlorotrimethylsilane. The effectiveness of the reaction has been explored for a large variety of aldehydes with Lewis acids and fluorides as catalysts.
- Bellassoued, Moncef,Lensen, Nathalie,Bakasse, Mina,Mouelhi, Sinda
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p. 8785 - 8789
(2007/10/03)
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- ALPHA-MERCAPTOACRYLIC ACID DERIVATIVES HAVING CALPAIN INHIBITORY ACTIVITY
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The invention covers a novel series of α-mercaptoacrylic acid derivatives that inhibit both calpain I and calpain II with a high affinity and selectivity. The compounds are useful in the treatment of neurodegenerative disorders including cerebrovascular disorders, brain injury, spinal cord, and peripheral nerve injury, cardiac infarction, cataracts, inflammation, restenosis, muscular dystrophy, and platelet aggregation. Pharmaceutical compositions, methods of using processes for preparing and novel intermediates useful in the processes are also disclosed.
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- 4-substituted azetidinones as precursors to 2-substituted-3-carboxy carbapenem antibiotics and a method of producing them
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New 4-substituted azetidinones having the formulae I and II: STR1 wherein X is oxygen, sulfur or a moiety of the formula NR6 where R1, R2, R3, R4, R5 and R6 are defined hereafter, which are intermediates for the preparation of carbapenem and carbacephem antibacterials and processes for producing such antibacterials through the utilization of an acid mediated ring closure reaction.
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- 4-substituted azetidinones as precursors to 2-substituted-3-carboxy carbapenem antibiotics and a method of producing them
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New 4-substituted azetidinones having the formulea I and II: STR1 with R1, R2, R3, R4, R5 and X defined hereafter, which are intermediates for the preparation of carbapenem and carbacephem antibacterials and processes for producing such antibacterials through the utilization of an acid mediated ring closure reaction.
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- Preparation of 5-methylbutyrolactone
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5-Methylbutyrolactone is prepared by a process in which a pentenoic ester of the formula I where X is CH2 =CH--CH2 --CH2 --, CH3 --CH=CH--CH2 -- or CH3 --CH2 --CH=CH-- and R is alkyl, cycloalkyl, aralkyl or aryl, or a mixture of these esters is reacted with water at from 50° to 350° C. in the presence or absence of a diluent a) over a zeolite and/or phosphate catalyst or b) in the presence of from 0.01 to 0.25 mole of a sulfonic acid, a Lewis acid and/or a non-oxidizing mineral acid per mole of pentenoic ester or over from 0.1 to 40% by weight, based on the pentenoic ester, of a strongly acidic ion exchanger as a catalyst in a first stage, or the pentenoic ester of the formula I, where X and R have the stated meanings, is hydrolyzed in a first stage with the aid of a strongly acidic ion exchanger as a catalyst to give the pentenoic acid of the formula I, where R is hydrogen, and the resulting pentenoic acid is subjected to cyclization in a second stage in the presence of from 0.005 to 0.1 mole of a sulfonic acid, a Lewis acid or a non-oxidizing mineral acid per mole of pentenoic acid or over from 0.1 to 20% by weight, based on the pentenoic acid, of a strongly acidic ion exchanger at from 50° to 350° C.
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- Reactions of 2-(2-propenyl)-3-chloromethyloxirane with benzene
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The reaction of 2-(2-propenyl)-3-chloromethyloxirane with benzene in the presence of aluminum chloride gives a 3:6:1 mixture of 1,4-dichloro-2-hexanone, 1-chloro-4-phenyl-2-hexanone, and 1-chloro-3,4-diphenyl-2-hexanone
- Akhmedov, M.A.,Sardarov, I.K.,Akhmedov, I.M.,Kostikov, R.R.,Babaev, N.M.,Shukyurova, M.B.
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p. 2025 - 2028
(2007/10/02)
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- Investigations on the Selectivity of the β-Scission of Alkyl-Radicals, II - Selectivity of the β-Fragmentation of α-(Methoxycarbonyl)alkyl Radicals
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The rate of β-scission of α-(methoxycarbonyl)alkyl radicals 3 and 9, generated by addition of cycloalkyl radicals to appropriate methyl 2-methylenealkanoates 1 and methyl (E)-2-alkenoates 8, resp., has been measured relative to the hydrogen transfer from cycloalkanes.The rate of β-scission increases with increasing stability of the leaving radical R*.Polar effects reversing the stability sequence have also been observed, e.g. the more stable (methoxycarbonyl)methyl radical leaves more slowly than a less stable secondary alkyl radical.
- Metzger, Juergen O.,Klenke, Kurt
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p. 875 - 879
(2007/10/02)
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- STADIES ON THE WITTIG REACTION (VIII). STEREOSELECTIVITY OF DIPHENYL ALLYLIC PHOSPHONIUM YLIDS IN WITTIG REACTION
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Ylids generated from diphenyl allylic phosphonium salts reacted with aliphatic aldehydes containing a terminal oxygen functionized group in the absence of lithium salt to give E,E-conjugated dienes.The stereoselectivity depends mainly on the base used, the allylic part of phosphonium salts also shows some effect on stereochemistry.Eight conjugated dienic insect sex pheromones and related analogues with different E-selectivities were obtained.
- Wenfang, Huang,Jun, Zhu,Wenjing, Xiao,Yanneng, Deng
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- Straightforward Synthesis of 2-Alkenoic Acids from the Corresponding Saturated Aldehydes
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2-Alkenoic acids may be prepared in good yields from saturated aldehydes via α-selenenylation with 4-(phenylseleno)morpholine formed in situ, followed by hydrogen peroxide oxidation.The actual oxidizing agent is benzeneperseleninic acid which is formed in the reaction medium.
- Outurquin, Francis,Paulmier, Claude
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p. 690 - 691
(2007/10/02)
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- STEREOSELECTIVE SYNTHESIS OF (E)-α,β-UNSATURATED ACIDS FROM C,O,O-TRI(TRIMETHYLSILYL) KETENE ACETAL AND ALDEHYDS
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Aldehydes are converted into (E)-α,β-unsatured carboxylic acids by means of C,O,O-tri(trimethylsilyl) ketene acetal and a catalytic a mount of ZnBr2.
- Bellasoued, Moncef,Gaudemar, Marcel
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p. 4551 - 4554
(2007/10/02)
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- Process for the preparation of unsaturated aliphatic carboxylic acids
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The invention relates to a process for the preparation of unsaturated aliphatic carboxylic acids by thermal cracking of the polymeric intermediate product ("polyester") which is formed in the catalytic reaction of aldehydes or ketones with ketene. The reaction mixture containing polyester is heated with water, and the polyester is then isolated and subjected to cracking. Or the polyester is first isolated and then heated with water and finally subjected to cracking. In both cases the temperature when the mixture is heated with water is the same as the boiling point, or is less than 40° C. below the boiling point, of the aqueous mixture.
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- Synthese und fluessigkristalline Eigenschaften 2,6-disubstituierter Naphtaline
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The syntheses and the mesomorphic properties of a series of novel 2,6-disubstituted naphthalenes are described. 4-benzonitriles 5 and 4-benzonitriles 8 exhibit wide-range nematic mesophases. 6,6'-Di(n-Alkyl)-2,2'-binaphthyls 6 have been isolated as by-products from the reaction mixtures of 5.Some of these novel compounds have polymorphic properties.The esters 13 and 15 of 4-(6-hydroxy-2-naphthyl)benzonitrile show enhanced mesophase stabilities which reach maximum values in the series of α,β-unsaturated esters 15.The 4-(n-pentyl)benzoate 14 of the same (hydroxynaphthyl)benzonitrile has a melting point of 125 deg and a clearing point of > 310 deg.This particular derivative belongs to those liquid-crystalline compounds having the broadest purely nematic-phase range.In addition, (RS)-4-(2-pentyl-6-chromanyl)benzonitrile (20) and three compounds with two and four laterally arranged CN groups at the bicyclooctene, bicyclooctadiene, and phenyl-ring systems 31-33 were synthesized.Only 20 shows mesomorphic properties.
- Lauk, Urs H.,Skrabal, Peter,Zollinger, Heinrich
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p. 1406 - 1426
(2007/10/02)
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- Base-Catalyzed Reactions of α,β-Unsaturated Esters and Nitriles. 4. Dimerization of β-Alkyl-Substituted Acrylates
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2-Butenoates 1-C4 alkyl, cyclohexyl, or 1-bornyl> and higher β-alkyl-substituted acrylates 2-C9 n-alkyl> undergo highly selective (>95percent) dimerization in the presence of promoted potassium or sodium catalysts to yield corresponding 2-alkylidene-3-alkylglutarates (3).The reaction involves metalation of the β-alkylacrylate at the C-2 position, followed by addition at C-3 of a second monomeric molecule.Changes in the relative extent of dimerization (Kr) as a function of structural and experimentalvariables were determined.Kr is strongly dependent upon the inductive and steric characteristics of the alcoholic (R) group and of the β-alkyl substituent (R').For an n-alkyl group as R' the Kr value increases with increase in chain length from C1 to C4 but then decreases for longer substituents (C5-C9).Among the two geometric isomers in the dimeric product 3, the isomer with an α-vinylic hydrogen cis to the carboalkoxy group is predominant in all cases, but its relative concetration decreases with an increase in the size of R'.Branched or cyclic β-substituents in 2 prevent dimerization due to steric hindrance in the rate-determining addition step.Promoted potassium or sodium catalysts show much higher dimerization activity compared to supported alkali metals or to alkoxides.For conversions of up to 60percent, Kr values in proton-exchanging alkylbenzene solvents and in nonexchanging alkylcyclohexanes are closely similar, indicating faster abstraction of an α-vinylic hydrogen from the monomer, rather than a benzylic hydrogen from the solvent, in the chain regeneration step of the reaction.
- Shabtai, Joseph,Ney-Igner, Eva
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p. 3795 - 3802
(2007/10/02)
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