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Malonate
Kinds of Malonate Terms modified by Malonate Selected AbstractsMalonate induces cell death via mitochondrial potential collapse and delayed swelling through an ROS-dependent pathwayBRITISH JOURNAL OF PHARMACOLOGY, Issue 4 2005Francisco J Fernandez-Gomez 1Herein we study the effects of the mitochondrial complex II inhibitor malonate on its primary target, the mitochondrion. 2Malonate induces mitochondrial potential collapse, mitochondrial swelling, cytochrome c (Cyt c) release and depletes glutathione (GSH) and nicotinamide adenine dinucleotide coenzyme (NAD(P)H) stores in brain-isolated mitochondria. 3Although, mitochondrial potential collapse was almost immediate after malonate addition, mitochondrial swelling was not evident before 15 min of drug presence. This latter effect was blocked by cyclosporin A (CSA), Ruthenium Red (RR), magnesium, catalase, GSH and vitamin E. 4Malonate added to SH-SY5Y cell cultures produced a marked loss of cell viability together with the release of Cyt c and depletion of GSH and NAD(P)H concentrations. All these effects were not apparent in SH-SY5Y cells overexpressing Bcl-xL. 5When GSH concentrations were lowered with buthionine sulphoximine, cytoprotection afforded by Bcl-xL overexpression was not evident anymore. 6Taken together, all these data suggest that malonate causes a rapid mitochondrial potential collapse and reactive oxygen species production that overwhelms mitochondrial antioxidant capacity and leads to mitochondrial swelling. Further permeability transition pore opening and the subsequent release of proapoptotic factors such as Cyt c could therefore be, at least in part, responsible for malonate-induced toxicity. British Journal of Pharmacology (2005) 144, 528,537. doi:10.1038/sj.bjp.0706069 [source] ChemInform Abstract: An Enantioselective Michael Addition of Malonate to Nitroalkenes Catalyzed by Low Loading Demethylquinine Salts in Water.CHEMINFORM, Issue 11 2008Fu-Xin Chen Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Rh(II)-Catalyzed Enantioselective Cyclopropanation of Olefins with Dimethyl Malonate via in situ Generated Phenyliodonium Ylide.CHEMINFORM, Issue 11 2005Paul Mueller Abstract For Abstract see ChemInform Abstract in Full Text. [source] Studies on K2CO3 -Catalyzed 1,4-Addition of 1,2-Allenic Ketones with Diethyl Malonate: Controlled Selective Synthesis of ,,,-Unsaturated Enones and ,-Pyrones.CHEMINFORM, Issue 13 2004Shengming Ma Abstract For Abstract see ChemInform Abstract in Full Text. [source] ChemInform Abstract: Asymmetric Michael Reaction of Diethyl Malonate with Crotonaldehyde Catalyzed by Chiral Aminocarboxylates, Amino Alcoholates, and Amino Phenolates.CHEMINFORM, Issue 23 2002K. A. Kochetkov Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] ChemInform Abstract: Dimethyl Malonate as a One-Carbon Source: A Novel Method of Introducing Carbon Substituents onto Aromatic Nitro Compounds.CHEMINFORM, Issue 4 2002N. Selvakumar Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Better Performance of Monodentate P -Stereogenic Phosphanes Compared to Bidentate Analogues in Pd-Catalyzed Asymmetric Allylic AlkylationsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 21 2010Arnald Grabulosa Abstract The cationic allylpalladium complexes 3a,3f, 4a, 4e, 5e of type [Pd(,3 -2-Me-C3H4)P2]PF6 were synthesized using a group of monodentate P -stereogenic phosphanes, P=PPhRR, (a,f) and diphosphanes (PhRPCH2)2 (1a, 1e) or PhRPCH2Si(Me)2CH2PPhR (2e). The analogous cationic complexes with the disubstituted allyl group (,3 -1,3-Ph2 -C3H3) and monodentate phosphanes were not isolated as stable solids; only [PdCl(,3 -1,3-Ph2 -C3H3)P] (6a, 6d) were obtained. Palladium allyl complexes were screened as precatalysts in the allylic substitution of rac -3-acetoxy-1,3-diphenyl-1-propene (I) and (E)-3-acetoxy-1-phenyl-1-propene (III) with dimethyl malonate as the nucleophile. The various catalytic precursors showed a wide range of activity and selectivity. The bismonodentate phosphane complexes 3 are more active than the bidentate analogues. With regard to the regioselectivity, precursors containing monodentate phosphanes favour the formation of the linear product in the allylic substitution of cinnamyl acetate (III) compared with those containing bidentate phosphanes. With substrate I, compounds with the diphosphanes 1a and 1e, containing a five-membered chelate ring, gave low enantioselectivities (less than 10,% ee), but those with the diphosphane 2e, forming a six-membered chelate ring or with two monodentate phosphanes, afforded products with moderate enantioselectivity under standard conditions (ee up to 74,%). The results show that the performance of precursors containing monodentate phosphanes was superior to those containing bidentate ligands in both activity and selectivity. [source] Syntheses, Crystal Structures and Magnetic Properties of Carboxylato-Bridged Polymeric Networks of MnIIEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 2 2006Subal Chandra Manna Abstract Three new carboxylato-bridged polymeric networks of MnII having,molecular formula [Mn(ox)(dpyo)]n (1), {[Mn2(mal)2(bpee)(H2O)2]·0.5(bpee)·0.5(CH3OH)}n (2) and {[Mn3(btc)2(2,2,-bipy)2(H2O)6]·4H2O}n (3) [dpyo, 4,4,-bipyridine N,N,-dioxide; bpee, trans -1,2 bis(4-pyridyl)ethylene; 2,2,-bipy, 2,2,-bipyridine; ox = oxalate dianion; mal = malonate dianion; btc = 1,3,5-benzenetricarboxylate trianion] have been synthesized and characterized by single-crystal X-ray diffraction studies and low temperature magnetic measurements. Structure determination of complex 1 reveals a covalent bonded 2D network containing bischelating oxalate and bridging dpyo; complex 2 is a covalent bonded 3D polymeric architecture, formed by bridging malonate and bpee ligands, resulting in an open framework with channels filled by uncoordinated disordered bpee and methanol molecules. Whereas complex 3, comprising btc anions bound to three metal centers, is a 1D chain which further extends its dimensionality to 3D via - and H-bonding interactions. Low temperature magnetic measurements reveal the existence of weak antiferromagnetic interaction in all these complexes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source] Hexaazamacrocycle Containing Pyridine and Its Dicopper Complex as Receptors for Dicarboxylate AnionsEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 22 2005Feng Li Abstract The host,guest binding interactions of the hexaazamacrocycle [26]py2N4, in its tetraprotonated form H4[26]py2N44+ as well as in its dicopper(II) complex [Cu2([26]py2N4)(H2O)4]4+, with dicarboxylate anions of different stereoelectronicrequirements, such as oxalate (ox2,), malonate (mal2,), succinate (suc2,), fumarate (fu2,) and maleate (ma2,), were evaluated. The association constants were determined using potentiometric methods in aqueous solution, at 298.0 K and 0.10 mol·dm,3 KCl. These values for the tetraprotonated ditopic receptor with the dicarboxylate anions revealed that the main species in solution corresponds to the formation of {H4[26]py2N4(A)}2+ (pH , 4,9), A being the substrate anion. The values determined are not especially high, but the receptor exhibits selectivity for the malonate anion. The study of the cascade complexes revealed several species in solution, involving mononuclear and dinuclear complexes, mainly protonated and hydrolysed species, as well as the expected complexes [Cu2([26]py2N4)(A)(H2O)x]2+ or [Cu2([26]py2N4)(A)2(H2O)y]. Ox2, and mal2, form cascade complexes with only one anion, which will necessarily bridge the two copper atoms because of the symmetrical arrangement of the dinuclear complex. The two other studied anions, suc2, and ma2,, form species involving two substrate anions, although species with only one suc2, anion were also found. UV/Vis and EPR spectroscopy have shown that the dicopper complex can operate as a sensor to detect and quantitatively determine oxalate spectrophotometrically because of the red shift of the maximum of the visible band observed by addition of ox2, to an aqueous solution of the dinuclear copper complex. However the selectivity of [Cu2([26]py2N4)(H2O)4]4+ as a receptor for ox2, in the studied series is not sufficiently high to detect ox2, spectrophotometrically in the presence of the other anions. Molecular dynamics simulations indicated that the H4[26]py2N44+ receptor provides a large and flexible cavity to accommodate the studied anions. Molecular recognition is based in electrostatic interactions rather than in multiple hydrogen-bonding interactions acting cooperatively. By contrast, the [Cu2([26]py2N4)]4+ receptor has a well-shaped cavity with adequate size to uptake these anions as bridging ligands with formation of four Cu,O bonds. The ox2, anion is encapsulated within the cascade complex while the remaining anions are located above the N6 macrocyclic plane, suggesting a selective coordination behaviour of this receptor. In spite of our molecular simulation being carried out in gas phase, the modelling results are consistent with the solution studies. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005) [source] Bromodimethylsulfonium Bromide Catalyzed Three-Component Mannich-Type ReactionsEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 5 2008Abu T. Khan Abstract Bromodimethylsulfonium bromide catalyzes Mannich-type reactions of a variety of aldimines, generated in situ from aldehydes and anilines, with enolizable ketones or diethyl malonate in three-component reactions to afford the corresponding ,-amino carbonyl compounds. The salient features of this protocol are: shorter reaction times, simplicity of the procedure, good to excellent yields, avoidance of aqueous workup and column-chromatographic separations, and high stereoselectivities.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] A Radical Version of the Bromo- and the Iodocyclization of Bis(homoallylic) Alcohols , The Synthesis of Halogenated Tetrahydrofurans by Stereoselective Alkoxyl Radical Ring ClosuresEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 20 2003Jens Hartung Abstract A new synthesis of bromo- and iodomethyl-substituted tetrahydrofurans has been devised. The sequence starts with the conversion of aryl-functionalized bis(homoallylic) alcohols 1 into N -alkenoxythiazole-2(3H)-thiones 6 or pyridine-2(1H)-thiones 7. When photolyzed in the presence of appropriate trapping reagents, thiones 6 and 7 efficiently liberated substituted 4-penten-1-oxyl radicals 2, which underwent synthetically useful 5- exo -trig cyclizations. Cyclized radicals 3 were trapped with BrCCl3 or an adequate iodine atom donor (either n -C4F9I or diethyl 2-iodo-2-methyl malonate) to provide halocyclization products 4 or 5. This strategy has been applied for the synthesis of 3-, 4-, or 5-phenyl-substituted 2-(1-bromo-1-methylethyl)tetrahydrofurans 4a,c (75,90%, 36,96% de), which were not attainable as major products from polar, for example NBS-mediated, bromocyclizations. Aryl-substituted 2-iodomethyl tetrahydrofurans 5 (46,80%) were prepared in a similar way starting from N -alkenoxypyridine-2(1H)-thiones 7 and a suitable iodine atom donor. Diastereomerically pure iodides cis - 5 and trans - 5 served as starting materials for a stereochemical analysis of disubstituted tetrahydrofurans by NMR spectroscopy and X-ray diffraction analysis. The results of this investigation clarified that all new alkoxyl radical cyclizations followed in terms of regio- and diastereoselectivity the general guidelines which had been established for this type of ring-closure reaction. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Identification and characterization of a novel transcriptional regulator, MatR, for malonate metabolism in Rhizobium leguminosarum bv. trifoliiFEBS JOURNAL, Issue 24 2000Hwan Young Lee A novel gene, matR, located upstream of matABC, transcribed in the opposite direction, and encoding a putative regulatory protein by sequence analysis was discovered from Rhizobium leguminosarum bv. trifolii. The matA, matB, and matC genes encode malonyl-CoA decarboxylase, malonyl-CoA synthetase, and a presumed malonate transporter, respectively. Together, these enzymes catalyze the uptake and conversion of malonate to acetyl-CoA. The deduced amino-acid sequence of matR showed sequence similarity with GntR from Bacillus subtilis in the N-terminal region encoding a helix-turn-helix domain. Electrophoretic mobility shift assay indicated that MatR bound to a fragment of DNA corresponding to the mat promoter region. The addition of malonate or methylmalonate increased the association of MatR and DNA fragment. DNase I footprinting assays identified a MatR binding site encompassing 66 nucleotides near the mat promoter. The mat operator region included an inverted repeat (TCTTGTA/TACACGA) centered ,46.5 relative to the transcription start site. Transcriptional assays, using the luciferase gene, revealed that MatR represses transcription from the mat promoter and malonate alleviates MatR-mediated repression effect on the expression of Pmat -luc+ reporter fusion. [source] Cannabinoid CB2 receptor agonists protect the striatum against malonate toxicity: Relevance for Huntington's diseaseGLIA, Issue 11 2009Onintza Sagredo Abstract Cannabinoid agonists might serve as neuroprotective agents in neurodegenerative disorders. Here, we examined this hypothesis in a rat model of Huntington's disease (HD) generated by intrastriatal injection of the mitochondrial complex II inhibitor malonate. Our results showed that only compounds able to activate CB2 receptors were capable of protecting striatal projection neurons from malonate-induced death. That CB2 receptor agonists are neuroprotective was confirmed by using the selective CB2 receptor antagonist, SR144528, and by the observation that mice deficient in CB2 receptor were more sensitive to malonate than wild-type animals. CB2 receptors are scarce in the striatum in healthy conditions, but they are markedly upregulated after the lesion with malonate. Studies of double immunostaining revealed a significant presence of CB2 receptors in cells labeled with the marker of reactive microglia OX-42, and also in cells labeled with GFAP (a marker of astrocytes). We further showed that the activation of CB2 receptors significantly reduced the levels of tumor necrosis factor-, (TNF-,) that had been increased by the lesion with malonate. In summary, our results demonstrate that stimulation of CB2 receptors protect the striatum against malonate toxicity, likely through a mechanism involving glial cells, in particular reactive microglial cells in which CB2 receptors would be upregulated in response to the lesion. Activation of these receptors would reduce the generation of proinflammatory molecules like TNF-,. Altogether, our results support the hypothesis that CB2 receptors could constitute a therapeutic target to slowdown neurodegeneration in HD. © 2008 Wiley-Liss, Inc. [source] Rhodium(II)-Catalyzed Inter- and Intramolecular Cyclopropanations with Diazo Compounds and Phenyliodonium Ylides: Synthesis and Chiral AnalysisHELVETICA CHIMICA ACTA, Issue 2 2005Ashraf Ghanem Different classes of cyclopropanes derived from Meldrum's acid (=2,2-dimethyl-1,3-dioxane-4,6-dione; 4), dimethyl malonate (5), 2-diazo-3-(silyloxy)but-3-enoate 16, 2-diazo-3,3,3-trifluoropropanoate 18, diazo(triethylsilyl)acetate 24a, and diazo(dimethylphenylsilyl)acetate 24b were prepared via dirhodium(II)-catalyzed intermolecular cyclopropanation of a set of olefins 3 (Schemes,1 and 4,6). The reactions proceeded with either diazo-free phenyliodonium ylides or diazo compounds affording the desired cyclopropane derivatives in either racemic or enantiomer-enriched forms. The intramolecular cyclopropanation of allyl diazo(triethylsilyl)acetates 28, 30, and 33 were carried out in the presence of the chiral dirhodium(II) catalyst [Rh2{(S)-nttl)4}] (9) in toluene to afford the corresponding cyclopropane derivatives 29, 31 and 34 with up to 37% ee (Scheme,7). An efficient enantioselective chiral separation method based on enantioselective GC and HPLC was developed. The method provides information about the chemical yields of the cyclopropane derivatives, enantioselectivity, substrate specifity, and catalytic activity of the chiral catalysts used in the inter- and intramolecular cyclopropanation reactions and avoids time-consuming workup procedures. [source] 5-Chloro-3-methylthio-1,2,4-thiadiazol-2-ium chlorides as useful synthetic precursors to a variety of 6a,4 -thiapentalene systemsHETEROATOM CHEMISTRY, Issue 1 2003Georges Morel Title salts 3 were easily obtained by treatment of formimidoyl isothiocyanates 1 with a twofold excess of methanesulfenyl chloride. They showed interesting chemical behavior toward several nitrogen and carbon nucleophiles. Substitution reactions with isothioureas and acetamide in the presence of triethylamine gave the 1H, 6H -6a,4 -thia-1,3,4,6-tetraazapentalenes 7 and 6H -6a,4 -thia-1-oxa-3,4,6-triazapentalene 9, respectively. Addition of p -toluidine furnished the 5-imino-thiadiazole derivatives 10, which reacted further with diverse heterocumulenes to yield the corresponding thiatriaza- and tetraazapentalene species 11. The N,N,-bis(1,2,4-thiadiazol-5-ylidene)diaminobenzenes 13 were also prepared and reacted with phenyl isothiocyanate. Two stable rotational isomers were separated for the 1,2-phenylene product 14b. Other ,-hypervalent sulfur compounds 16 were synthesized under similar conditions from salts 3 and methyl cyanoacetate or dimethyl malonate. The structural assignments were discussed on the basis of IR and NMR spectroscopic data and received additional support from X-ray analysis of substrate 16a. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:95,105, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10106 [source] Kinetic study of the condensation of salicylaldehyde with diethyl malonate in a nonpolar solvent catalyzed by secondary aminesINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2009Szczepan Bednarz The kinetics of condensation between salicylaldehyde and diethylmalonate in a toluene solution in the presence of secondary amines (i.e., piperidine and 4-piperidinopiperidine) as catalysts was investigated. It was found that the reaction proceeds via the Knoevenagel mechanism, and the kinetic model was numerically verified. © 2009 Wiley Periodicals, Inc. Int J Chem Kinet 41: 589,598, 2009 [source] Reactivity of selected volatile organic compounds (VOCs) toward the sulfate radical (SO4,)INTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2001Ch. George Rate constants for a series of alcohols, ethers, and esters toward the sulfate radical (SO4,) have been directly determined using a laser photolysis set-up in which the radical was produced by the photodissociation of peroxodisulfate anions. The sulfate radical concentration was monitored by following its optical absorption by means of time resolved spectroscopy techniques. At room temperature the following rate constants were derived: methanol ((1.6 ± 0.2) × 107 M,1 s,1); ethanol ((7.8 ± 1.2) × 107 M,1 s,1); tert -butanol ((8.9 ± 0.3) × 105 M,1 s,1); diethyl ether ((1.8 ± 0.1) × 108 M,1 s,1); MTBE ((3.13 ± 0.02) × 107 M,1 s,1); tetrahydrofuran (THF) ((2.3 ± 0.2) × 108 M,1 s,1); hydrated formaldehyde ((1.4 ± 0.2) × 107 M,1 s,1); hydrated glyoxal ((2.4 ± 0.2) × 107 M,1 s,1); dimethyl malonate (CH3OC(O)CH2C(O)OCH3) ((1.28 ± 0.02) × 106 M,1 s,1); and dimethyl succinate (CH3OC(O)CH2CH2C(O)OCH3) ((1.37 ± 0.08) × 106 M,1 s,1) where the errors represent 2,. For the two latter species, we also measured the temperature dependence of the corresponding rate constants. A correlation of these kinetics with the bond dissociation energy is also presented and discussed. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 539,547, 2001 [source] An Efficient and General Microwave-Assisted Copper-Catalyzed Conia-Ene Reaction of Terminal and Internal Alkynes Tethered to a Wide Variety of CarbonucleophilesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 13 2010Sonia Montel Abstract This paper describes a highly efficient, microwave-assisted, Conia-ene reaction of alkynes bearing a stabilizing carbon nucleophile. The reaction, catalyzed by a commercially available copper catalyst, proceeds under neutral conditions and is generally applicable even to less reactive nucleophiles such as malonate, cyanoacetate, and sulfonylacetate derivatives. This copper-mediated cycloisomerization is also applicable to internal unactivated alkynes leading exclusively to the corresponding 5-membererd products having an E -olefinic chemistry. [source] Mixed Isobutylphobane/N-Heterocyclic Carbene Ruthenium- Indenylidene Complexes: Synthesis and Catalytic Evaluation in Olefin Metathesis ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 11-12 2010Xavier Sauvage Abstract Two new second generation ruthenium(II) dichloride-indenylidene complexes [RuCl2(9-isobutylphosphabicyclo[3.3.1]nonane)(NHC)(3-phenyl-1-indenylidene)], where NHC=1,3-bis(2,4,6-trimethylphenyl)imidazolin-2-ylidene (SIMes) or its unsaturated imidazol-2-ylidene analogue (IMes), were isolated in high yields upon heating a tetrahydrofuran (THF) solution of the diphosphane complex [RuCl2(isobutylphobane)2(3-phenyl-1-indenylidene)] with a two-fold excess of the corresponding imidazol(in)ium-2-carboxylate zwitterions. Both products were characterized by 1H, 13C, and 31P,NMR spectroscopy, and the molecular structure of [RuCl2(isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was determined by X-ray diffraction analysis. A close inspection of the packing structure revealed the presence of different types of intra- and intermolecular interactions that enhanced the global stability of the crystals, while low temperature NMR experiments showed the existence of two distinct rotational isomers due to the unsymmetrical nature of the phobane ligand. The catalytic activity of both compounds was assessed in olefin metathesis using benchmark ring-opening metathesis polymerization, ring-closing metathesis (RCM), and cross-metathesis reactions, and compared with those of related first and second generation ruthenium-benzylidene and indenylidene catalyst precursors. Kinetic studies confirmed the high thermal stability of the mixed isobutylphobane/N-heterocyclic carbene complexes, which suffered from a slow initiation efficiency compared to other catalytic systems based on the tricyclohexylphosphane ligand. However, the remarkable robustness of [RuCl2(isobutylphobane)(SIMes)(3-phenyl-1-indenylidene)] was beneficial for performing the RCM of diethyl 2,2-bis(2-methylallyl)malonate. Monitoring the formation of the ruthenium-methylidene active species [RuCl2(isobutylphobane)(SIMes)(CH2)] derived from this precursor further demonstrated its ability to sustain long reaction times and high temperatures required to carry out the RCM of tetrasubstituted olefins. [source] Novel Cinchona -Aminobenzimidazole Bifunctional OrganocatalystsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 18 2009Lei Zhang Abstract Efficient Cinchona -derived chiral 2-aminobenzimidazole catalysts were prepared by the coupling of 5,7-bis(trifluoromethyl)-2-chlorobenzimidazole with C(9S)-aminodihydroquinine or C(9R)-aminodihydroquinidine and successively applied to the Michael addition of dimethyl malonate to nitroolefins as very efficient chiral Lewis acid bifunctional organocatalysts (up to >99% ee). [source] Novel [Ruthenium(substituted-tetramethylcyclopentadiene) (2-quinolinecarboxylato)(allyl)] Hexafluorophosphate Complexes as Efficient Catalysts for Highly Regioselective Nucleophilic Substitution of Aliphatic Allylic SubstratesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2008Hui-Jun Zhang Abstract Stable [ruthenium(R-substituted-tetramethylcyclopentadiene)(2-quinolinecarboxylato)(1-R,-substituted-allyl) hexafluorophosphate (R=Me, R,=H, Me, n- Pr, Ph; R=t- Bu, R,=Me) and [ruthenium(pentamethylcyclopentadiene)(2-quinolinecarboxylato)(1- n -propylallyl)] tetrafluoroborate (4,a), as allylruthenium(IV) complexes, have been synthesized in one step, starting from [ruthenium(R-substituted-tetramethylcyclopentadiene)tris(acetonitrile) hexafluorophosphate or tetrafluoroborate complexes, quinaldic acid, and allylic alcohols. Single stereoisomers are obtained and the X-ray single crystal structure determinations of 3b (R=t- Bu, R,=Me) and 4,a allow one to specify the preferred arrangement. Complexes 3a (R=R,=Me) and 3b are involved as precatalysts favoring the formation of branched products in regioselective nucleophilic allylic substitution reactions, starting from ethyl 2- (E) -hexen-1-yl carbonate and chlorohexene as unsymmetrical aliphatic allylic substrates. Phenols, dimethyl malonate, and primary (aniline) and secondary (pyrrolidine, piperidine) amines have been used as nucleophiles under mild basic conditions. For the first time, the regioselectivity in favor of the branched product obtained from purely aliphatic allylic substrates is close to the high regioselectivity previously reached starting from cinnamyl-type substrates in the presence of ruthenium catalysts. [source] Memory Effects in Palladium-Catalyzed Allylic Alkylations of 2-Cyclohexen-1-yl AcetateADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 17-18 2007Nina Svensen Abstract The objective of this work was to characterize the enantiospecificity of the allylic alkylation of enantioenriched 2-cyclohexen-1-yl acetate with the enolate ion of dimethyl malonate catalyzed by unsymmetrical palladium catalysts. The precatalysts employed were (,3 -allyl)PdLCl, where L is a monophosphine ligand [PPh3, PCy3, P(2-BiPh)Cy2, or P(t- Bu)3], all of which afforded enantiospecificity to some extent (5,47,%). Quantum mechanical calculations show that, theoretically, the enantiospecificity should be high due to a preference for the "trans to P" transition state in both formation of the ,3 -allyl intermediate and nucleophilic attack. However, the observed enantiospecificity is relatively low due to isomerization of the ,3 -allyl intermediate and/or dynamic equilibria between the catalytically active (,3 -allyl)PdLCl species and [(,3 -allyl)PdL2]+ or [(,3 -allyl)PdCl]2. It was also observed experimentally that increasing the bulk of the phosphine inhibits formation of the [(,3 -allyl)PdL2]+ complexes, significantly increasing the observed enantiospecificity for some of the ligands. [source] New Recoverable Poly(ethylene glycol)-Supported C1 - Diamino-oligothiophene Ligands for Palladium-Promoted Asymmetric Allylic Alkylation (AAA) ReactionsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 12-13 2006Marco Bandini Abstract A new class of chiral C1 -symmetrical diamino-oligothiophene ligands easy-grafted on a soluble polymeric support (MeOPEG5000) is described. The diamines were found to be effective promoting agents for the [Pd(0)]-catalysed asymmetric allylic alkylation (AAA) of dimethyl malonate in high yields and excellent enantioselectivity (ee up to 99,%). The supported chiral ligand was readily recovered by precipitation and filtration was recycled up to three times without an appreciable loss in activity. The recycle of the organometallic catalytic system was also investigated. [source] Synthesis of 3-Carboxylic derivatives of 1,5-benzodiazepinesJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 3 2001O. Mansour A series of 3-carboxylic derivatives of disubstituted 1,5-benzodiazepines (5,9) was synthesized by hetero-cyclisation from 1,2-diaminobenzene (1) with dibenzoylmethane (2) followed by bromination on position 3 and by introduction of the carboxylic group or introduction of the malonic moiety. Reduction of the hetero-cycle gave the perhydro derivative diethyl (2,4-diphenyl-1,2,4,5-tetrahydro-3H -1,5-benzodiazepin-3-yl)malonate (9). [source] The synthesis of [3,4,1,- 13C3]genisteinJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 14 2007Mark F. Oldfield Abstract A facile synthesis is described for [3,4,1,- 13C3]genistein for use as an internal standard in isoflavone analysis by mass spectrometric methods. Ethyl 4-hydroxy[1- 13C]benzoate was first prepared from the reaction of diethyl [2- 13C]malonate and 4H -pyran-4-one. Two further 13C atoms were incorporated using potassium [13C]cyanide as the source to give 4,-benzyloxy-[1,2,1,- 13C3]phenylacetonitrile. [3,4,1,- 13C3]Genistein was then constructed through coupling of the isotopically labelled phenylacetonitrile with phloroglucinol under Hoesch conditions, followed by formylation and cyclization. Copyright © 2007 John Wiley & Sons, Ltd. [source] On-line glucose and lactate monitoring in rat striatum: effect of malonate and correlation with histological damageJOURNAL OF NEUROCHEMISTRY, Issue 2003J. Skjoeth-Rasmussen Microdialysis of glucose, lactate and glycerol was performed to monitor brain insults and to predict brain injury in a rat model using the mitochondrial toxin malonate (5,100 mm). Striatal dialysates were analyzed off-line using a CMA 600 microdialysis analyzer or on-line using flow-injection analysis and biosensors for glucose and lactate. Histological damage was evaluated using stereological principles. Lactate (baseline ca. 1 mm) was dose-dependently increased, reaching a maximum of five- to six-fold increase, whereas glucose (baseline 1,2 mm) was decreased (>50%) by malonate >20 mm. These changes were reversible upon perfusion with normal Ringer's. Transient increases in glycerol (four- to eight-fold) were only observed in some rats, and were not dose-dependent. Histological damage was related to the perfused malonate concentration, but was not significantly correlated with lactate or glycerol changes. [source] Some novel accelerating agents for nitroxide-mediated living free-radical polymerizationJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2005Huang Jianying Abstract Malononitrile (MN), trifluoroacetic acid anhydride, acetylacetone, acetoacetic ester, and diethyl malonate have been identified as novel rate-accelerating additives for nitroxide-mediated living free-radical polymerization. Among these additives, MN has the greatest accelerating effect. Adding MN at an MN/2,2,6,6-tetramethylpiperidine-oxyl (TEMPO) molar ratio of 4.0 results in a nearly 20 times higher rate of polymerization of styrene (St), and adding MN at an MN/TEMPO molar ratio of 2.5 results in a nearly 15 times higher rate of copolymerization of St and methyl methacrylate. The polymerization of St proceeds in a living fashion, as indicated by the increase in the molecular weight with time and conversion and the relatively low polydispersity. The polymerization rate of St is so quick that the conversion reaches 70% within 1 h at 125 °C when the molar ratio of MN to TEMPO is 4:1. Moreover, the reaction temperature can be reduced to 110 °C. A possible explanation for this effect is that the formation of hydrogen bonds between the MN and TEMPO moiety weakens the CON bond at the end of the polymer chain. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 5246,5256, 2005 [source] Synthesis and characterization of novel crosslinkable polymers with a nonlinear optical chromophore as a pendant groupJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 22 2001Sung-Ho Jin Abstract New crosslinkable polymers with a nonlinear optical (NLO) active chromophore as a pendant group were synthesized by condensation chain polymerization via palladium-catalyzed carbon,carbon coupling reactions. The polymerization yields were almost quantitative between the diiodobenzene (DIB) and diethyldipropargyl malonate (DEDPM) or 4-(dimethylamino)-4,-(6-dipropargylacetoxypropylsulfonyl)stilbene (DASS-6) monomers. To improve the molecular weight and mechanical properties of the NLO active polymer, we carried out the copolymerization with DIB and DASS-6 with various feed ratios of DEDPM. The resulting polymers were soluble in organic solvents and spun-cast onto indium tin oxide-coated glass substrates to make thin films. The molecular structures of the resulting polymers were characterized with various instrumental methods to confirm the carbon,carbon coupling reactions between the DIB and diacetylene monomers. The absorption of the ultraviolet,visible spectrum of the resulting polymers was drastically reduced after thermal curing at 160 °C because of the crosslinking of the reactive acetylene group in the polymer backbone. The electrooptic coefficient (r33) measured at 1.3 ,m ranged from 7 to 15 pm/V. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 4025,4034, 2001 [source] A comparative study of several HPLC methods for determining free amino acid profiles in honeyJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9-10 2005José Luis Bernal Abstract A study of the viability of three derivatizing reagents for obtaining amino acid profiles in honey through high performance liquid chromatography (HPLC) is presented. A method using diode array detection based on a reaction with diethyl ethoxymethylene malonate (DEMM) and two other methods using fluorescence detection based on derivatization with fluorenylmethyl chloroformate (FMOC-Cl) and 6-aminoquinolyl- N -hydroxysuccinimidyl carbamate (AQC) have been developed. The three methods yield detection limits close to the ppb level, but vary in relation to other analytical characteristics. The use of methyl chloroformate derivatives allows the profile to be obtained with the greatest sensitivity within a short time frame. On applying such methods to honey samples of diverse botanical origin, we observe that the proline values obtained are always lower than those found using the official spectrophotometric method, thereby underlining the advisability of using HPLC methods to reduce uncertainty in these results. [source] Liquid chromatography coupled to nuclear magnetic resonance spectroscopy for the identification of isoflavone glucoside malonates in T. pratense L. leaves.JOURNAL OF SEPARATION SCIENCE, JSS, Issue 13 2004Eva de Rijke Abstract Previous studies revealed that the main isoflavones in extracts of leaves of T. pratense L. are biochanin A and formononetin, their 7- O -glucosides, and two glucoside malonate isomers of each of them. Since LC,MS(/MS) did not provide sufficient information to distinguish the glucoside malonate isomers, in the present paper LC,NMR as well as off-line two-dimensional NMR were used to obtain further structural information. Matrix solid-phase dispersion (MSPD) was applied to obtain sufficiently high analyte concentrations to perform LC,NMR. Stop-flow reversed-phase LC,NMR was performed using a gradient of deuterated water and deuterated acetonitrile. Off-line COSY and NOESY experiments were carried out to determine the positions of the glucose moiety on the flavonoid aglycone, and of the malonate moiety on the glucose. Based on the fragmentation patterns in MS/MS and the NMR spectra, the two formononetin glucoside malonate isomers were identified as 7- O -,-D-glucoside 6´´- O -malonate and 7- O -,-D-glucoside 4´´- O -malonate; i.e. they only differ in the substitution position of the malonate group on the glucoside ring. The biochanin A glucoside malonate isomers, however, have quite different structures. The main and later eluting isomer is biochanin A 7- O -,-D-glucoside 6´´- O -malonate, and the minor and earlier eluting isomer is 5-hydroxy-7-methoxyisoflavone 4´- O -,-D-glucoside 4´´- O -malonate: the positions of the methoxy group and the glucoside 6´´- O -malonate group on the flavonoid skeleton are interchanged. [source] | |||||||||||||||||||||||||||||||||||||