- A methodical selection process for the development of ketones and esters as bio-based replacements for traditional hydrocarbon solvents
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A "top down" approach to the development of sustainable, greener, low-polarity solvents is presented. Methyl butyrate, ethyl isobutyrate, methyl pivalate and pinacolone were identified as potential target solvents from trends in Hansen solubility parameters and known physical properties. Solubility, flammability and physical properties were determined which showed their potential to replace traditional, hazardous, volatile, non-polar solvents such as toluene. Each new candidate then demonstrated their suitability to replace these traditional solvents in solubility tests, despite being esters and ketones, each candidate demonstrated their similarity to traditional volatile non-polar solvents in terms of their solubility properties by their ability to dissolve natural rubber, a particularly low-polarity solute. This was reinforced by their performance in a model Menschutkin reaction and a radical-initiated polymerisation for the production of pressure-sensitive adhesives, where their performance was found to be similar to that of toluene. Importantly, a preliminary toxicity test (Ames test) suggested non-mutagenicity in all candidates. Each of the four candidates can be synthesised via a catalytic route from potentially renewable resources, thus enhancing their green credentials.
- Byrne, Fergal P.,Forier, Bart,Bossaert, Greet,Hoebers, Charly,Farmer, Thomas J.,Hunt, Andrew J.
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Read Online
- Unified Approach to Imidodiphosphate-Type Br?nsted Acids with Tunable Confinement and Acidity
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We have designed and realized an efficient and operationally simple single-flask synthesis of imidodiphosphate-based Br?nsted acids. The methodology proceedsviaconsecutive chloride substitutions of hexachlorobisphosphazonium salts, providing rapid access to imidodiphosphates (IDP), iminoimidodiphosphates (iIDP), and imidodiphosphorimidates (IDPi). These privileged acid catalysts feature a broad acidity range (pKafrom ~11 to 95:5 er) sulfoxidation of methyln-propyl sulfide. Furthermore, the methodology delivers a novel, rationally designed super acidic catalyst motif, imidodiphosphorbis(iminosulfonylimino)imidate (IDPii), the extreme reactivity of which exceeds commonly employed super-Br?nsted acids, such as trifluoromethanesulfonic acid. The unique reactivity of one such IDPii catalyst has been demonstrated in the first α-methylation of a silyl ketene acetal with methanol as the electrophilic alkylating reagent.
- Schwengers, Sebastian A.,De, Chandra Kanta,Grossmann, Oleg,Grimm, Joyce A. A.,Sadlowski, Natascha R.,Gerosa, Gabriela G.,List, Benjamin
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supporting information
p. 14835 - 14844
(2021/09/18)
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- Catalytic conversion of ketones to esters: Via C(O)-C bond cleavage under transition-metal free conditions
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The catalytic conversion of ketones to esters via C(O)-C bond cleavage under transition-metal free conditions is reported. This catalytic process proceeds under solvent-free conditions and offers an easy operational procedure, broad substrate scope with excellent selectivity, and reaction scalability. This journal is
- Subaramanian, Murugan,Ramar, Palmurukan M.,Rana, Jagannath,Gupta, Virendra Kumar,Balaraman, Ekambaram
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supporting information
p. 8143 - 8146
(2020/09/09)
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- Nickel-catalysed direct alkylation of thiophenes via double C(sp3)-H/C(sp2)-H bond cleavage: The importance of KH2PO4
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A Ni-catalyzed oxidative C-H/C-H cross-dehydrogenative coupling (CDC) reaction was developed for constructing various highly functionalized alkyl (aryl)-substituted thiophenes. This method employs thiophenes and aliphatic (aromatic) amides that contain an 8-aminoquinoline as a removable directing group in the presence of a silver oxidant. The approach enables the facile one-step synthesis of substituted thiophenes with high functional group compatibility via double C-H bond cleavage without affecting C-Br and C-I bonds. DFT calculations verify the importance of KH2PO4 as an additive for promoting C-H bond cleavage and support the involvement of a Ni(iii) species in the reaction.
- Wang, Xie,Xie, Peipei,Qiu, Renhua,Zhu, Longzhi,Liu, Ting,Li, You,Iwasaki, Takanori,Au, Chak-Tong,Xu, Xinhua,Xia, Yuanzhi,Yin, Shuang-Feng,Kambe, Nobuaki
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supporting information
p. 8316 - 8319
(2017/07/26)
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- Acid-catalyzed oxidation of levulinate derivatives to succinates under mild conditions
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Levulinate derivatives are an attractive platform for the production of renewable chemicals. Here we report on the oxidation of methyl levulinate into dimethyl succinate with peroxides under mild conditions using Br?nsted and Lewis acid catalysts. Selectivities to succinate and acetate derivatives of approximately 60 and 40 %, respectively, were obtained with strong Br?nsted acids in methanol. Although the molecular structure (i.e., carbon-chain length and branching around the C=O group) and the oxidant type affect the product distribution, solvent choice has the strongest impact on changing the location of oxygen insertion into the carbon backbone. Specifically, switching the solvent from methanol to heptane resulted in a decrease in the succinate/acetate ratio from 1.6 to 0.3. In contrast to Br?nsted acids, we demonstrate that the nature of the metal cation is responsible for changing the reaction selectivity of water-tolerant Lewis acidic triflate salts.
- Wang, Yuran,Vogelgsang, Ferdinand,Román-Leshkov, Yuriy
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p. 916 - 920
(2015/03/18)
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- Methyl salicylate as a selective methylation agent for the esterification of carboxylic acids
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Methyl salicylate is a selective and inexpensive methylating agent for the esterification of carboxylic acids with a wide range of functional group tolerance. The intramolecular hydrogen bonds between the carboxylate and hydroxyl groups in methyl salicylate are essential for the transformation. Allyl, benzyl, methallyl, and propargyl salicylates can also be used as alkylating agents for the preparation of the corresponding alkyl carboxylates.
- Chen, Si,Jia, Lei,Li, Xiaonan,Luo, Meiming
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p. 263 - 268
(2014/03/21)
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- Design and synthesis of sulfonated carbons with amphiphilic properties
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A new type of sulfonated carbon material with amphiphilic properties was synthesized by the hydrothermal carbonization of a mixture of furfural-sodium dodecylbenzene sulfonate at 180 °C in an autoclave. The addition of SDBS is necessary for the production of materials with long carbon chains and is possibly used to improve the solubilization of long carbon-chain and steric compounds such as pivalic acid. The resulting material was characterized by N2 adsorption, XPS, 13C NMR, XRD and FTIR. The synthesized material was proven to be a highly efficient solid-acid catalyst in reactions such as the esterification of pivalic acid with alcohols, and catalytic performance much better than that of conventional solid acid catalysts, e.g. Amberlyst-15 and Nafion resin, was observed.
- Jia, Rong,Ren, Jiawen,Liu, Xiaohui,Lu, Guanzhong,Wang, Yanqin
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p. 11195 - 11201
(2014/07/21)
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- SUBSTITUTED HETEROAROMATIC PYRAZOLE-CONTAINING CARBOXAMIDE AND UREA DERIVATIVES AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted heteroaromatic pyrazole-containing carboxamide and urea derivatives as vanilloid receptor ligands, to pharmaceutical compositions containing these compounds and also to these compounds for use in the treatment and/or prophylaxis of pain and further diseases and/or disorders.
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Page/Page column 104
(2013/03/26)
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- Substituted Heteroaromatic Pyrazole-Containing Carboxamide and Urea Compounds as Vanilloid Receptor Ligands
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Substituted heteroaromatic pyrazole-containing carboxamide and urea compounds as vanilloid receptor ligands, pharmaceutical compositions containing these compounds and also to a method of using these compounds for treating and/or inhibiting pain and further diseases and/or disorders.
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Paragraph 0666
(2013/03/26)
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- SUBSTITUTED PYRAZOLYL-BASED CARBOXAMIDE AND UREA DERIVATIVES BEARING A PHENYL MOIETY SUBSTITUTED WITH AN N-CYCLIC GROUP AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted pyrazolyl-based carboxamide and urea derivatives bearing a phenyl moiety substituted with an N-cyclic group as vanilloid receptor ligands formula (S) to pharmaceutical compositions containing these compounds of the general formula (S) and also to these compounds for use in the treatment and/or prophylaxis of pain and further diseases and/or disorders.
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Page/Page column 46
(2013/05/23)
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- SUBSTITUTED PYRAZOLYL-BASED CARBOXAMIDE AND UREA DERIVATIVES BEARING A PHENYL MOIETY SUBSTITUTED WITH AN O-CONTAINING GROUP AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted pyrazolyl-based carboxamide and urea derivatives of formula (Q) as vanilloid receptor ligands, to pharmaceutical compositions containing these compounds and also to these compounds for use in the treatment and/or prophylaxis of pain and further diseases and/or disorders.
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Page/Page column 67
(2013/05/23)
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- SUBSTITUTED PYRAZOLYL-BASED CARBOXAMIDE AND UREA DERIVATIVES BEARING A PHENYL MOIETY SUBSTITUTED WITH A CO-CONTAINING GROUP AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted pyrazolyl-based carboxamide and urea derivatives bearing a phenyl moiety substituted with a CO-containing group as vanilloid receptor ligands, to pharmaceutical compositions containing these compounds and also to these compounds for use in the treatment and/or prophylaxis of pain and further diseases and/or disorders.
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Page/Page column 48
(2013/05/23)
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- SUBSTITUTED PYRAZOLYL-BASED CARBOXAMIDE AND UREA DERIVATIVES BEARING A PHENYL MOIETY SUBSTITUTED WITH AN SO2-CONTAINING GROUP AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted pyrazolyl-based carboxamide and urea derivatives bearing a phenyl moiety substituted with a S02-containing group as vanilloid receptor ligands, to pharmaceutical compositions containing these compounds and also to these compounds for use in the treatment and/or prophylaxis of pain and further diseases and/or disorders.
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Page/Page column 48
(2013/05/23)
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- SUBSTITUTED PYRAZOLYL-BASED CARBOXAMIDE AND UREA DERIVATIVES BEARING A PHENYL MOIETY SUBSTITUTED WITH AN N-CONTAINING GROUP AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted pyrazolyl-based carboxamide and urea derivatives of formula (R) bearing a phenyl moiety substituted with an N-containing group as vanilloid receptor ligands, to pharmaceutical compositions containing these compounds and also to these compounds for use in the treatment and/or prophylaxis of pain and further diseases and/or disorders.
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Page/Page column 56
(2013/05/23)
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- Conversion of levulinate into succinate through catalytic oxidative carbon-carbon bond cleavage with dioxygen
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Grand Cleft Oxo: Levulinate, available from biomass, is oxidized into succinate through manganese(III)-catalyzed selective cleavage of C-C bonds with molecular oxygen. In addition to levulinate, a wide range of aliphatic methyl ketones also undergo oxidative C-C bond cleavage at the carbonyl group. This procedure offers a route to valuable dicarboxylic acids from biomass resources by nonfermentive approaches. Copyright
- Liu, Junxia,Du, Zhongtian,Lu, Tianliang,Xu, Jie
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p. 2255 - 2258
(2014/01/06)
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- Pb(II)-promoted amide cleavage: Mechanistic comparison to a Zn(II) analogue
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Two new Pb(II) complexes of the amide-appended nitrogen/sulfur epppa (N-((2-ethylthio)ethyl)-N-((6-pivaloylamido-2-pyridyl)methyl)-N-((2-pyridyl) methyl)amine) chelate ligand, [(epppa)Pb(NO3)2] (4-NO 3) and [(epppa)Pb(ClO4)2] (4-ClO4), were prepared and characterized. In the solid state, 4-NO3 exhibits κ5-epppa chelate ligand coordination as well as the coordination of two bidentate nitrate ions. In acetonitrile, 4-NO3 is a 1:1 electrolyte with a coordinated NO3-, whereas 4-ClO4 is a 1:2 electrolyte. Treatment of 4-ClO4 with 1 equiv Me4NOH·5H2O in CH3CN:CH 3OH (3:5) results in amide methanolysis in a reaction that is akin to that previously reported for the Zn(II) analogue [(epppa)Zn](ClO 4)2 (3-ClO4). 1H NMR kinetic studies of the amide methanolysis reactions of 4-ClO4 and 3-ClO4 as a function of temperature revealed free energies of activation of 21.3 and 24.5 kcal/mol, respectively. The amide methanolysis reactions of 4-ClO 4 and 3-ClO4 differ in terms of the effect of the concentration of methanol (saturation kinetics for 4-ClO4; second-order behavior for 3-ClO4), the observation of a small solvent kinetic isotope effect (SKIE) only for the reaction of the Zn(II)-containing 3-ClO4, and the properties of an initial intermediate isolated from each reaction upon treatment with Me4NOH·5H2O. These experimental results, combined with computational studies of the amide methanolysis reaction pathways of 4-ClO4 and 3-ClO4, indicate that the Zn(II)-containing 3-ClO4 initially undergoes amide deprotonation upon treatment with Me4NOH·5H2O. Subsequent amide protonation from coordinated methanol yields a structure containing a coordinated neutral amide and methoxide anion from which amide cleavage can then proceed. The rate-determining step in this pathway is either amide protonation or protonation of the leaving group. The Pb(II)-containing 4-ClO4 instead directly forms a neutral amide-containing, epppa-ligated Pb(II)-OH/Pb(II)-OCH3 equilibrium mixture upon treatment with Me4NOH·5H2O in methanol. The rate-determining step in the amide methanolysis pathway of 4-ClO4 is nucleophilic attack of the Pb(II)-OCH3 moiety on the coordinated amide. Overall, it is the larger size of the Pb(II) center and the availability of coordination positions that enable direct formation of a Pb(II)-OH/Pb(II)- OCH3 mixture versus the initial amide deprotonation identified in the reaction of the Zn(II)-containing 3-ClO4.
- Elton, Eric S.,Zhang, Tingting,Prabhakar, Rajeev,Arif, Atta M.,Berreau, Lisa M.
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p. 11480 - 11492
(2013/10/22)
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- A mild and clean Baeyer-Villiger oxidation of ketones using sodium peroxydisulfate as oxidant catalyzed by silica-supported aluminum chloride
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Sodium peroxydisulfate was used as the oxidant for Baeyer-Villiger oxidation of a variety of cyclic and acyclic ketones at room temperature in the presence of Silica-supported aluminum chloride (silica-AlCl3) as catalyst. The catalyst was prepared by a simple procedure, which exhibited high catalytic activity for the Baeyer- Villiger oxidation of ketones using environmental friendly sodium peroxydisulfate as oxidizing agent. Iranian Chemical Society 2012.
- Mahmoodi, Nosrat Ollah,Heirati, Seyedeh Zahra Dalil,Ekhlasi-Kazaj, Kamel
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p. 521 - 528
(2013/02/22)
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- Substituted Cyclic Carboxamide and Urea Derivatives as Ligands of the Vanilloid Receptor
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Substituted cyclic carboxamide and urea compounds, a process for their preparation, pharmaceutical compositions containing these compounds, and the use of these compounds for the treatment and/or inhibition of pain and other conditions mediated by the vanilloid receptor 1.
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Page/Page column 28
(2012/03/10)
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- Substituted Heteroaromatic Carboxamide and Urea Compounds as Vanilloid Receptor Ligands
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Substituted heteroaromatic carboxamide and urea compounds corresponding to formula (i) processes for the preparation thereof, pharmaceutical compositions containing these compounds and also a method of using these compounds in pharmaceutical compositions for treating or inhibiting pain and other conditions mediated at least in part via the vanilloid receptor 1.
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Page/Page column 33
(2012/05/20)
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- SUBSTITUTED BICYCLIC CARBOXAMIDE AND UREA DERIVATIVES AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted bicyclic carboxamide and urea derivatives, to processes for the preparation thereof, to pharmaceutical compositions containing these compounds and also to the use of these compounds for preparing pharmaceutical compositions.
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Page/Page column 72
(2012/05/31)
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- SUBSTITUTED HETEROAROMATIC CARBOXAMIDE AND UREA DERIVATIVES AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted heteroaromatic carboxamide and urea derivatives of formula (I), to processes for the preparation thereof, to pharmaceutical compositions containing these compounds and also to the use of these compounds for preparing pharmaceutical compositions.
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Page/Page column 73
(2012/05/31)
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- Substituted Bicyclic Carboxamide and Urea Compounds as Vanilloid Receptor Ligands
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Substituted bicyclic carboxamide and urea compounds corresponding to formula (I) processes for the preparation thereof, pharmaceutical compositions containing these compounds, and a method of using these compounds for the treatment and/or inhibition of pain and other conditions mediated at least in part via the vanilloid receptor 1.
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Page/Page column 28
(2012/05/20)
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- Double molecular recognition with aminoorganoboron complexes: Selective alcoholysis of β-dicarbonyl derivatives
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Double duty: Aminoorganoboron (AOB) complexes recognize alcohol and β-dicarbonyl units, and thereby facilitate chemo- and site-selective alcoholysis of the latter (see scheme). The complex activates both reaction partners. This strategy enables C-C, C-N, and C-O bond cleavage in addition/elimination reactions under near neutral pH conditions and provides a new method for functional group conversions. Copyright
- Oishi, Shunsuke,Saito, Susumu
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p. 5395 - 5399
(2012/06/18)
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- Chemoselective esterification and amidation of carboxylic acids with imidazole carbamates and ureas
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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)
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- SUBSTITUTED AROMATIC CARBOXAMIDE AND UREA DERIVATIVES AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted aromatic carboxamide and urea derivatives, to processes for the preparation thereof, to pharmaceutical compositions containing these compounds and also to the use of these compounds for preparing pharmaceutical compositions (formula (I)).
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Page/Page column 95
(2010/11/18)
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- SUBSTITUTED PHENYLLUREAS AND PHENYLAMIDES AS VANILLOID RECEPTOR LIGANDS
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The invention relates to substituted phenylureas and phenylamides of formula (I), to processes for the preparation thereof, to pharmaceutical compositions containing these compounds and also to the use of these compounds for preparing pharmaceutical compositions.
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Page/Page column 78
(2010/11/18)
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- N-Heterocyclic carbene-catalyzed oxidations
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N-Heterocyclic carbenes catalyze the oxidation of allylic and benzylic alcohols as well as saturated aldehydes to esters with manganese(IV) oxide in excellent yields. A variety of esters can be synthesized, including protected carboxylates. The oxidation proceeds under mild conditions, with low loadings of a simple triazolium salt pre-catalyst in the presence of base. Substrates containing potentially epimerizable centers are oxidized while preserving stereochemical integrity. The acyl triazolium intermediate generated under catalytic conditions can be employed as a chiral acylating agent in the desymmetrization of meso-diols.
- Maki, Brooks E.,Chan, Audrey,Phillips, Eric M.,Scheidt, Karl A.
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experimental part
p. 3102 - 3109
(2009/09/05)
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- N-heterocyclic carbene-catalyzed oxidation of unactivated aldehydes to esters
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(Chemical Equation Presented) N-Heterocyclic carbenes catalyze the oxidation of unactivated aldehydes to esters with manganese(IV) oxide in excellent yield. The reaction proceeds through a transient activated alcohol, which when generated in situ allows for the selective oxidation of the aldehyde under mild conditions. These conditions successfully oxidize potentially epimerizable aldehydes and alcohols while preserving stereochemical integrity. A variety of ester derivatives can be synthesized with variation of the acylated alcohol as well as the unactivated aldehyde.
- Maki, Brooks E.,Scheldt, Karl A.
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supporting information; experimental part
p. 4331 - 4334
(2009/06/06)
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- Transformation of tertiary amines into alkylating reagents by treatment with 2-chloro-4,6-dimethoxy-1,3,5-triazine. A synthetic application of side-reaction accompanying coupling by means of 4-(4,6-dimethoxy-[1,3,5] triazin-2-yl)-4-methyl-morpholin-4-ium chloride (DMTMM)
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Mild reaction conditions are described for the preparation of a number of alkyl chlorides and 2-dialkyl(aryl)amino-4,6-dirnethoxy-1,3,5-triazines by dealkylation of quaternary triazinylammonium chlorides formed as reactive intermediates in reaction of tertiary amines with 2-chloro-4,6-dimethoxy-1,3,5- triazine. The high selectivity of substitution was observed within the reactivity order of the alkyl groups: benzyl ~ allyl > methyl > n-alkyl. Studies on dealkylation of S-(-)-J-dimethyl-(1-phenylethyl)amine to R-(+)-1-chloro-1-phenylethane revealed that reaction proceeded with an inversion of configuration on the carbon atom as may be expected for SN2 type substitution. The scope of reaction was extended by exchange of anion in quaternary triazinylammonium chlorides with 1-, SCN-, C6H5O-, CH3COO- followed by N-dealkylation step.
- Kolesinska,Kaminski
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experimental part
p. 2115 - 2123
(2009/04/07)
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- Effective high-pressure cleavage of sterically hindered steroid esters
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A simple and effective method to deprotect of sterically hindered steroid esters is described. Deprotection was carried out in MeOH in the presence of a catalytic amount of Et3N under high-pressure conditions. Enzymatic, anionite, and high-pressure methods are compared.
- Kroszczynski, Wojciech,Olszewska, Ewa,Salanski, Piotr,Jurczak, Janusz
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p. 1488 - 1492
(2007/10/03)
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- Cobalt-catalyzed photolytic methoxycarbonylation of bromoalkanes in the presence of a Lewis acid
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Addition of a water-stable Lewis acid, indium trichloride, improved the rate of photochemical methoxycarbonylation of bromoalkanes. Primary and secondary bromoalkanes were carbonylated in good yields. Carbonylation of tertiary substrates was somewhat more difficult and some of them reacted too slowly for the reaction to be of a preparative value.
- Cash, Daniel,Combs, Angela,Dragojlovic, Veljko
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p. 1143 - 1145
(2007/10/03)
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- Trialkyl acetic acid (neo acid) esters and esterification process
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Disclosed is a method of making trialkyl acetic acid (“neo acid”) esters and a neo acid ester composition. Neo acid esters are made by contacting a neo acid stream, comprising a mixture of neo acids, with alcohol in the presence of a catalyst. The invention has the benefit of providing a desired neo acid ester composition, while eliminating, or at least limiting, the need for separation and/or purification of the reactants prior to the synthesis of the desired neo acid esters.
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- Facile oxidation of aldehydes to acids and esters with Oxone
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(Matrix presented) A highly efficient, mild, and simple protocol is presented for the oxidation of aldehydes to carboxylic acids utilizing Oxone as the sole oxidant. Direct conversion of aldehydes in alcoholic solvents to their corresponding ester products is also reported. These reactions may prove to be valuable alternatives to traditional metal-mediated oxidations.
- Travis, Benjamin R.,Sivakumar, Meenakshi,Hollist, G. Olatunji,Borhan, Babak
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p. 1031 - 1034
(2007/10/03)
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- Production of esters
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Disclosed is a process for the production of esters. In particular, the process includes contacting an olefin or an ether with carbon monoxide and an acid composition comprising BF3.2CH3OH to from a product composition, adding an alcohol to the product composition, and separating the BF3.2CH3OH from the ester. The separated BF3.2CH3OH may then be recycled to the reaction unit.
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- Stereoselectivity of the intramolecular homolytic substitution in the induced decomposition of methacrylic-type peroxidic compounds
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Tile stereochemistry of the oxiranes, obtained by radical induced decomposition of various peroxydic compounds, was determined by NMR spectroscopy. The stereoselectivity of the intramolecular homolytic substitution on the peroxidic bond was discussed in relation to the effect of the reaction temperature and on the influence of structural factors such as the nature of the leaving and attacking radicals.
- Colombani, Daniel,Maillard, Bernard
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p. 14855 - 14864
(2007/10/03)
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- Gas-Phase Nucleophilic Displacement Reactions
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Displacement reactions of each of a variety of anionic nucleophiles reacting with each of a variety of neutrals have been studied by pulsed ion cyclotron resonance (ICR) spectroscopy.Rate constants for these reactions are interpreted in terms of a three-step reaction sequence.RRKM calculations are used to obtain information about the energy of transition states.The origin of the barrier to reaction in solution is discussed.
- Olmstead, William N.,Brauman, John I.
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p. 1653 - 1662
(2007/10/03)
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- Oxidation of Alkynes by Hydrogen Peroxide Catalyzed by Methylrhenium Trioxide
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The oxidation of alkynes with hydrogen peroxide is catalyzed by methylrhenium tioxide.The reactions can be rationalized by postulating that an oxirene intermediate is formed between a rhenium peroxide and the alkyne.Internal alkynes yield α-diketones and carboxylic acids, the latter from the complete cleavage of the triple bonds.Rearrangement products were observed only for aliphatic alkynes.Terminal alkynes gave carboxylic acids and their derivatives and α-keto acids as the major products, but their yields varied with the solvent used.
- Zhu, Zuolin,Espenson, James H.
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p. 7728 - 7732
(2007/10/03)
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- Preparation and thermal decomposition of N,N'-diacyl-N,N'-dialkoxyhydrazines: Synthetic applications and mechanistic insights
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Oxidation of various O-alkyl hydroxamates 1 where R1 was a keto-methoxime, benzoyl, aryl, or alkyl group with ceric ammonium nitrate (CAN) or nickel peroxide (NiO2·H2O) leads to the corresponding esters in high yield. This augurs well for the facile synthesis of highly hindered esters. Dimers of type 2 were identified as intermediates in these oxidations, and a combination of experimental and theoretical results suggest that these dimers decompose in a stepwise 1,1-elimination manner via intermediate nitrenes to furnish the esters and not via a stepwise 1,2-elimination sequence as previously thought.
- De Almeida, Mauro V.,Barton, Derek H. R.,Bytheway, Ian,Ferreira, J. Albert,Hall, Michael B.,Liu, Wansheng,Taylor, Dennis K.,Thomson, Lisa
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p. 4870 - 4874
(2007/10/02)
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- Adamantyl-Containing O-Monothioesters. II. Synthesis and Chemical Transformations of O-Methyl (1-Adamantyl)thioacetate in Reaction with Piperidine
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O-Methyl (1-adamantyl)thioacetate has been prepared for the first time by reaction of methyl (1-adamantyl)acetate with phosphorus pentasulfide in dioxane.The reaction of this product with piperidine yields corresponding S-ester, (1-adamantyl)aceto- and (1-adamantyl)thioacetopiperidides, and N-methylpiperidine.A mechanism of this reaction has been proposed, based on comparative analysis of behavior of O-methyl 1-adamantylthioacetate and its analogs, adamantane-1-thiocarboxylic and thiopivalic acid O-esters.
- Klimko, Yu. E.,Isaev, S. D.,Yurchenko, A. G.
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p. 166 - 170
(2007/10/02)
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- Synthesis and Thermolysis of Ketal Derivatives of 3-Hydroxy-1,2-dioxolanes
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3--3,4,4,5-tetramethyl-5-phenyl-1,2-dioxolane (2), 3-methoxy-3,4,4,5-tetramethyl-5-phenyl-1,2-dioxolane (3), and 3-acetoxy-3,4,4,5-tetramethyl-5-phenyl-1,2-dioxolane (4) were synthesized from the corresponding 3-hydroxy-1,2-dioxolane (1a) under basic conditions. 3-Acetoxy-4,4-dimethyl-3,5,5-triphenyl-1,2-dioxolane (5) was also synthesized via this approach.Under acidic conditions, 3-hydroxy-1,2-dioxolane 1a underwent quantitative decomposition to phenol and 3,3-dimethyl-2,4-pentanedione.This competing degradation was dependent on the nature of the substituents at position-5.Methyl groups at position-5 slowed the degradative rearrangement whereas phenyl groups favored it. 3-Methoxy- and 3-(allyloxy)-4,4,5,5-tetramethyl-3-phenyl-1,2-dioxolanes (6, 7) were synthesized under acidic conditions from the appropriate 1,2-dioxolane precursors and the corresponding alcohols.At 60 deg C, derivatized 1,2-dioxolanes 2-7 were found to be more stable than the corresponding 3-hydroxy-1,2-dioxolanes.The first order rate constants for the thermolysis of 1,2-dioxolanes 2-7 were determined.Product studies showed that thermolysis of 2-5 yielded pairs of ketones and derivatized carboxylic acids.In addition to R-group migration products, an acetoxy migration product was observed for the thermolysis of 4.Thermolysis of 6 at 60 deg C in benzene yielded methyl benzoate and pinacolone, quantitatively.Thermolysis of 7 yielded products analogous to those for 6.No evidence for internal trapping of radicals by the carbon-carbon double bond of the allyloxy group in 7 was found.The thermolysis appeared to proceed with peroxy bond homolysis as the rate-determining step.Subsequent β-scissions of the intermediate 1,5-oxygen diradical with interesting rearrangements that show a high preference for alkyl vs phenyl migration account for the observed product distributions.The results suggest that the β-scission/rearrangement mechanism may not be concerted but rather stepwise to yield 1,3-diradical and carbonyl fragments.
- Baumstark, A. L.,Vasquez, P. C.,Chen, Y.-X.
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p. 6692 - 6696
(2007/10/02)
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- Oxygen Atom Transfer With Niobocene Ketenes; Baeyer-Villiger Chemistry with Unusual Regioselectivities
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Niobocene ketene complex 1 has been utilized as an oxygen atom transfer reagent, converting ketones and aldehydes to esters and carboxylic acids.The steric properties of compound 1 give rise to a series of relative migratory aptitudes that differs from those seen for peracids.The process may be rendered catalytic in 1 with methyltrifluoromethyldioxirane (4). Key Words: Baeyer-Villiger reaction, niobocene complexes, ketenes, oxygen transfer, dioxiranes
- Fermin, Maria C.,Bruno, Joseph W.
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p. 7545 - 7548
(2007/10/02)
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- Dual Reaction Channels for Solvolyses of Acyl Chlorides in Alcohol-Water Mixtures
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Rate constants are reported for solvolyses at 0 deg C of trimethylacetyl chloride (3) in 90-30percent v/v acetonitrile-, acetone-, ethanol- and methanol-water mixtures, of adamantane-1-carbonyl chloride (4) in 90-60percent acetone-, ethanol- and methanol-water mixtures, and of cyclopropanecarbonyl chloride (5) in 90-40percent acetone-water.Quantitative product data (acid and ester) are also reported for solvolyses of trimethylacetyl chloride in 98-20percent ethanol- and methanol-water mixtures.Product selectivities (S) show maxima in 90-95percent alcohol-water mixtures, similar to those, reported previously for solvolyses of p-chlorobenzoyl chloride (1a), benzoyl chloride (1b), 2,4,6-trimethylbenzenesulfonyl chloride (2a) and 4-methoxy-2,6-dimethylbenzenesulfonyl chloride (2b).Using rate-rate profiles, logarithms of rate constants are dissected into the competing reaction channels.Given the sharp maxima in S that occur at different alcohol compositions for different substrates, and the link to 'breaks' in rate-rate profiles, the results are consistent with competing mechanisms having different rate-limiting steps.The competing mechanisms involve two broad reaction channels: (1) nucleophilic attack by one molecule of solvent assisted by a second molecule of solvent acting as a general base catalyst-consequently, in aqueous alcohol there are four mechanistic combinations operating simultaneously within this one reaction channel; (2) nucleophilic attack by solvent occurs via a carbocationic reaction within the SN2-SN1 mechanistic spectrum, involving for example, a solvent-separated ion pair intermediate (SN1) or a concerted nucleophilic attack (SN2).
- Bentley, T. William,Shim, Chang Sub
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p. 1659 - 1664
(2007/10/02)
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- E/Z Isomerization, Solvolysis, Addition, and Cycloaddition Reactions of (E)-tert-Butylketene Methyl tert-Butyldimethylsilyl Acetal
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In the presence of catalytic amounts of CF3COCH3 or CF3COCF3, the silyl ketene acetal E-1 was isomerized into its Z isomer (Z/E ratio 90:10).For this novel E/Z isomerization a mechanism is proposed, in which addition and reelimination of the fluoro ketone, through a 1,4-dipolar intermediate operates.With the protic nucleophiles CH3OH, CF3CH2OH, or PhOH, the ketene acetal E-1 afforded the ortho esters 2 as addition products, while CH3CO2H, CF3CO2H, or H2O led to methyl pivalate as the solvolysis product.This chemistry is readily explained through protonation of the ketene acetal E-1 to generate the corresponding carbenium ion.At low temperature the reaction with TCNE gave the silylketene imine 3 as labile cycloadduct, which underwent on workup desilylation to give the TCNE-incorporated ester 6; the latter eliminated hydrogen cyanide at room temperature to give the ene ester 7.With MTAD the labile silyl ene product 4 was obtained initially, which underwent silyl migration to give N-silylated urazole 8; final desilylation led to the stable urazole 9.Also for the ene reactions of TCNE and MTAD with the silyl ketene acetal E-1, a 1,4-dipolar intermediate is proposed to intervene.
- Adam, Waldemar,Wang, Xiaoheng
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p. 7244 - 7250
(2007/10/02)
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- Thermal Decomposition of t-Butyl(nitro)malononitrile: Evidence for the Generation of a T-Butyl Cation via Facile Carbon-Carbon Bond Heterolysis
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The decomposition of t-butyl(nitro)malononitrile in dimethyl sulphoxide at 80 deg C gives isobutene (65percent) as a product arising from a t-butyl cation generated via carbon-carbon bond heterolysis which proceeds eleven times faster than the carbon-chlorine bond heterolysis of t-butyl chloride.
- Mitsuhashi, Tsutomu,Hirota, Hiroshi
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p. 324 - 325
(2007/10/02)
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- PHOTOCHEMICAL CARBONYLATION OF ALKYL IODIDES IN THE PRESENCE OF VARIOUS METAL CARBONYLS
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Various transition metal complexes including group VII and VIII metal carbonyls are highly active catalyst precursors for the photochemical carbonylation of organic iodides at room temperature under an atmospheric pressure of carbon monoxide.Primary, secondary and tertiary alkyl iodides which have β-hydrogens on sp3-carbons were smoothly carbonylated by this catalyst system without β-hydride elimination to give the corresponding esters in yields of 63 - 88 percent.
- Kondo, Teruyuki,Tsuji, Yasushi,Watanabe, Yoshihisa
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p. 3833 - 3836
(2007/10/02)
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- Process for making esters
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Carboxylic acid esters are produced by the reaction of a carboxylic acid halide with a carbonate ester in the presence of an initiator. The reaction of a dicarboxylic acid dihalide and a bis(alkyl carbonate) ester produces a polymeric polyester.
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- Synthesis of Trialkylacetic Acids by the Anodic Oxidation of 3,3-Disubstituted-2-oxo Carboxylic Acids
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The "non-Kolbe" electrolysis of 3,3-disubstituted-2-oxocarboxylates 1-3 in methanol produced mixtures of methyl trialkylacetates 5, trialkylacetaldehydes 6, in some cases 2-hydroxy-3,3,3-trialkylpropionic acids 7, trialkylethylenes 8, and methyl trialkylmethyl ethers 9.When one of the substituents on the 3-carbon of the 2-oxo carboxylate was phenyl 4, molecular rearrangement was not observed.In addition to products 5-9, with the exception of 7, there was obtained with 4 an alkyl phenyl ketone 10.The methyl trisubstituted acetates were saponified to the desired trialkylacetic acids.
- Rabjohn, Norman,Cranor, W. L.,Schofield, C. M.
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p. 1732 - 1736
(2007/10/02)
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- Chlorination of Carboxylic Acid Derivatives. VIII. Liquid Phase Chlorination of the Aliphatic C5-Carboxylic Acids and Their Chlorides, Methyl Esters and Chloromethyl Esters with Chlorine
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The chlorination of pentanoic, 3-methylbutanoic, 2-methylbutanoic and 2,2-dimethylpropanoic acids and their derivatives with chlorine in the liquid phase have been investigated.The monochloro products formed were determined by gas-liquid chromatography (GLC) and gas-liquid chromatography-mass spectrometry (GLC-MS) as their esters through the comparison with authentic samples.The deactivation of position 2 decreases in the order COCl > CO2H > CO2CH2Cl > CO2CH3, the effect of the COCl-group in pentanoic acid derivatives being 4.3 times stronger than that of the CO2CH3-group.The deactivation is smallest in 2-methylbutanoic acid derivatives owing to the electron-donating methyl group.The EI mass spectra of the methyl and chloromethyl esters have been studied in detail.
- Kornonen, Ilpo O. O.
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p. 467 - 474
(2007/10/02)
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