EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2008
Jyoti Singh
Abstract The present work discusses the nickel chemistry in a set of amide-based open-chain ligands with subtle differences in the backbone or terminal amine substituents. The ligands coordinate to the Ni2+ ion through the Namide and Namine atoms maintaining a square-planar geometry. Absorption spectra and NMR studies reveal that the solid-state square-planar geometry is retained in solution. The electrochemical results suggest that the NiIII/NiII redox couple primarily depends on the N4 donors, which is composed of two Namide and twoNamine atoms and not on the peripheral substituents. All four ligands with variable backbone and substituents are equally competent in stabilizing the NiIII state. On the basis of electrochemical findings, chemical oxidations were carried out, and they reveal generation of the NiIII state in two cases, whereas decomposition was observed in others. Preliminary alkene epoxidation reactions suggest that the present nickel complexes transiently stabilize the higher oxidation state of the nickel ion that possibly participates in the oxidation of the substrates.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Synthesis, Coordination and Catalytic Utility of Novel Phosphanyl,ferrocenecarboxylic Ligands Combining Planar and Central Chirality

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2007
Martin Lama
Abstract The chiral ferrocene derivative (R,Rp)-2-[1-(diphenylphosphanyl)ethyl]ferrocenecarboxylic acid (1) is prepared together with selected derivatives resulting from modification at the phosphane moiety [P -oxide (5) and P -sulfide (4)] and the carboxyl group {amides bearing benzyl (6) and (R)- or (S)-1-phenylethyl substituents [(R)- 7 and (S)- 7] at the amide nitrogen atom}. Acid 1 and amide 6 are studied as ligands in rhodium and palladium complexes. Bridge cleavage of the dimer [{Rh(,-Cl)Cl(,5 -C5Me5)}2] with 1 gives [RhCl2(,5 -C5Me5)(1 -,P)] (9) containing P-monodentate 1, which undergoes smooth conversion to the (phosphanylalkyl)ferrocenecarboxylato complex [RhCl(,5 -C5Me5){Fe(,5 -C5H5)(,5 -C5H3 -1-CH(Me)PPh2 -2-COO-,2O,P}] (10) upon treatment with silica gel or alumina. Yet another O,P -chelate complex,[Rh{Fe(,5 -C5H5)(,5 -C5H3 -1-CH(Me)PPh2 -2-COO-,2O,P}(CO)(PCy3)] (11; Cy = cyclohexyl) is obtained directly by an acid-base reaction between the acetylacetonato complex [Rh(acac)(CO)(PCy3)] and 1. Amide 6 reacts with [{Pd(,-Cl)(,3 -C3H5)}2] to give the expected phosphane complex [PdCl(,3 -C3H5)(6 -,P)] (12), while the replacement of the cyclooctadiene (cod) ligand in [PdCl(Me)(cod)] affords the chelate complex [PdCl(Me)(6 -,2O,P)] (13). All compounds are characterised by spectroscopic methods and the solid-state structures of 5, 9, 11, 13, (R,Sp)-2-[1-(diphenylphosphoryl)ethyl]-1-[N -(R)-(1-phenylethyl)carbamoyl]ferrocene [(R)- 8; phosphane oxide from (R)- 7], and the synthetic precursors (R,Sp)-1-bromo-2-[1-(diphenylphosphanyl)ethyl]ferrocene (2) and (R,Sp)-1-bromo-2-[1-(diphenylthiophosphoryl)ethyl]ferrocene (3) determined by single-crystal X-ray diffraction. The catalytic properties of 1 and the amides are probed in enanatioselective rhodium-catalysed hydrogenation and palladium-catalysed asymmetric allylic alkylation. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Synthesis of Enantiopure 1-Aryl-1-butylamines and 1-Aryl-3-butenylamines by Diastereoselective Addition of Allylzinc Bromide to Imines Derived from (R)-Phenylglycine Amide

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2004
Jan Dalmolen
Abstract The synthesis of enantiopure 1-aryl-1-butylamines via a highly diastereoselective addition of allylzinc bromide to imines derived from (R)-phenylglycine amide is reported. These are synthesised by a three-step procedure, which involves: (a) formation of the chiral imines; (b) asymmetric addition of the allylzinc reagent; (c) removal of the chiral auxiliary by means of a reductive or non-reductive method. The reductive method provides 1-aryl-1-butylamines whereas the non-reductive method preserves the double bond to afford 1-aryl-3-butenylamines. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Construction of Recombinant Escherichia coli Catalysts which Simultaneously Express an (S)-Oxynitrilase and Different Nitrilase Variants for the Synthesis of (S)-Mandelic Acid and (S)-Mandelic Amide from Benzaldehyde and Cyanide

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 10 2009
Olga Sosedov
Abstract Recombinant Escherichia coli strains were constructed which simultaneously expressed the genes encoding the (S)-oxynitrilase from cassava (Manihot esculenta) together with the wild-type or a mutant variant of the arylacetonitrilase from Pseudomonas fluorescens EBC191 in a single organism under the control of a rhamnose-inducible promoter. The whole cell catalysts obtained converted benzaldehyde and potassium cyanide in aqueous media at pH,5.2 mainly to (S)-mandelic acid and/or (S)-mandelic amide and synthesized only low amounts of the corresponding (R)-enantiomers. The conversion of benzaldehyde and potassium cyanide (KCN) by a whole-cell catalyst simultaneously expressing the (S)-oxynitrilase and the wild-type nitrilase resulted in a ratio of (S)-mandelic acid to (S)-mandelic amide of about 4:3. This could be explained by the strong nitrile hydratase activity of the wild-type nitrilase with (S)-mandelonitrile as substrate. The relative proportion of (S)-mandelic amide formed in this system was significantly increased by coexpressing the (S)-oxynitrilase with a carboxy-terminally truncated variant of the nitrilase. This whole-cell catalyst converted benzaldehyde and KCN to mandelic amide and mandelic acid in a ratio of about 9:1. The ee of the (S)-mandelic amide formed was calculated to be >95%. [source]

Surface modification of PHBV films with different functional groups: Thermal properties and in vitro degradation

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2010
Yu Ke
Abstract Polyacrylamide was photografted on solution-cast poly(3-hydroxybutyric acid- co -3-hydroxyvaleric acid) (PHBV) films (amide-PHBV), on which amide groups were transformed into amine groups through Hofmann degradation reaction (amine-PHBV), followed by collagen coupling reaction to prepare collagen-modified PHBV (collagen-PHBV). Amide-, amine-, and collagen-PHBV had higher water absorption and d -spacing values than PHBV, and melting temperatures and enthalpies decreased in the order of collagen-PHBV < amine-PHBV < amide-PHBV < PHBV. Thermal decomposition kinetics of PHBV component in the films has been investigated by means of nonisothermal thermogravimetric and derivative thermogravimetric studies. Applying the Avrami-Erofeev equation with index of 2/5 as the probable kinetic function, the suitable activation energy was calculated by the Friedman method through linear fitting (correlation coefficient > 0.98). The activation energy of PHBV was lower than that of amide-PHBV but higher than that of amine- and collagen-PHBV. Being incubated in phosphate-buffered saline at 37°C, the modified PHBV films showed more weight loss than PHBV during 360 days; however, pH of degradation fluids was nearly neutral as the initial pH was recorded at 7.2. The modified PHBV films with different functional groups may provide an improved biodegradation rate for various cytocompatible biomaterials constructs. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Amide and lactam hydrolysis of N -(2-hydroxyacetyl)-2-pyrrolidone: effective catalysis,

JOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 11 2006
Lisaedy García Borboa
Abstract When N -(2-hydroxyacetyl)-2-pyrrolidone (open form) is dissolved in water at pH,>,8, irreversible cleavage of the exocyclic and endocyclic amide CN bond occurs. The latter rupture corresponds to the lactam opening yielding N -(4-hydroxyacetyl)butanoic acid (NBA). NBA is produced from the ester hydrolysis of the ester-amide macrocycle that is in equilibrium with the cyclol form of the open form. We have previously reported this latter equilibrium for N -(2-aminoacetyl)-2-lactams. 2-pyrrolidone (lactam) and glycolic acid are produced from direct hydrolysis of the open form by means of the amide exocyclic cleavage. The [NBA]/[lactam] ratio increases at higher pH since the NBA production is second order with respect to [OH,] while the corresponding lactam formation is only first order. The obtained kobs is hence the sum of the rate constants that yield lactam and NBA, respectively. This kobs is uncatalyzed and specific base catalyzed with unusually high rate constants of 2.1,×,10,6,s,1 and 0.025,M,1,s,1, respectively. The stability of the corresponding tetrahedral intermediate formed and the intramolecular alkoxy nucleophilic attack on the lactam carbonyl group combined with an effective protonation of the lactam nitrogen that promotes the CN cleavage, contribute to increase the reaction rates and lactam opening. Rate constants for the two parallel reactions are obtained from kobs and [NBA]/[lactam] versus pH plots. Copyright © 2006 John Wiley & Sons, Ltd. [source]

Mechanistic Insights into Direct Amide Bond Formation Catalyzed by Boronic Acids: Halogens as Lewis Bases,

ANGEWANDTE CHEMIE, Issue 38 2010
Dr. Tommaso Marcelli
Wasser raus! DFT-Rechnungen sagen voraus, dass eine Wassereliminierung aus einem tetraedrischen Intermediat der geschwindigkeitsbestimmende Schritt der Titelreaktion ist. Diese Umwandlung ist den Rechnungen zufolge hoch stereoselektiv und liefert cis -Amide als die kinetischen Produkte (siehe Schema). Die überlegene Aktivität von ortho -Halogenphenylboronsäuren resultiert aus dem Lewis-basischen Charakter von Halogenatomen. [source]

A Three-Coordinate Copper(II) Amide from Reductive Cleavage of a Nitrosamine,

ANGEWANDTE CHEMIE, Issue 5 2010
Marie
Ein NO-vum: Ein Kupfer(I)-,-diketiminat aktiviert das Nitrosamin Ph2NNO unter Bildung eines seltenen, dreifach koordinierten Kupfer(II)-amids, 1. Die Reaktion dieses Amids mit NO-Gas setzt Ph2NNO wieder frei und liefert eine gemischtvalente Spezies mit NO-funktionalisierten ,-Diketiminatliganden (2; Cu hellblau, N dunkelblau, O rot). Somit können an einem gewöhnlichen Kupferzentrum Spaltung und Bildung der R2N-NO-Bindung gleichermaßen stattfinden. [source]

Thin Films of ZrO2 for High- k Applications Employing Engineered Alkoxide- and Amide-Based MOCVD Precursors,

CHEMICAL VAPOR DEPOSITION, Issue 2-3 2007
R. Thomas
Abstract Ultrathin ZrO2 films were deposited on SiOx/Si in a multiwafer planetary metal-organic (MO)CVD reactor combined with a liquid delivery system. Two different alkoxide-based precursors, [Zr(OiPr)2(tbaoac)2] and [Zr(OtBu)2(tbaoac)2] are compared with two amide-based precursors, [Zr(NEt2)2(dbml)2] and [Zr(NEtMe)2(guanid)2]. Growth rate, surface roughness, density, and crystallization behavior are compared over a wide range of deposition temperatures (400,700,°C). In addition, the influence of the solvents, n -butylacetate, toluene, and hexane, is discussed. The best growth results in terms of low temperature deposition rate, surface roughness, film density, and carbon content were obtained for the new [Zr(NEtMe)2(guanid)2] precursor. The electrical properties were investigated with metal,insulator,semiconductor (MIS) capacitors. The relative dielectric permittivity was in the range 17,24, depending on the precursor. Compared to standard SiO2 capacitors of similar equivalent oxide thickness, low leakage currents were obtained. [source]

ChemInform Abstract: Highly Enantioselective Addition of Methyl Propiolate to Aldehydes Catalyzed by a Titanium(IV) Complex of a ,-Hydroxy Amide.

CHEMINFORM, Issue 24 2010
Tao Xu
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: Au(I)-Catalyzed Cycloisomerization Reaction of Amide- or Ester-Tethered 1,6-Enynes to Bicyclo[3.2.0]hept-6-en-2-ones.

CHEMINFORM, Issue 11 2010
Young Tak Lee
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: Chiral Amide from (1S,2R)-(+)-Norephedrine Alkaloid in the Enantioselective Addition of Diethylzinc to Aryl and Heteroaryl Aldehydes.

CHEMINFORM, Issue 4 2010
Nallamuthu Ananthi
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: Cu-Catalyzed Arylation of Phosphinic Amide Facilitated by (.+-.)-trans-Cyclohexane-1,2-diamine.

CHEMINFORM, Issue 22 2008
Juan Li
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]

Highly Diastereo- and Enantioselective Direct Aldol Reactions of Cycloketones with Aldehydes Catalyzed by a trans-4-tert-Butyldimethylsiloxy-L-proline Amide.

CHEMINFORM, Issue 27 2007
Long He
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, please click on HTML or PDF. [source]

Enhancement of Lithium Amide to Lithium Imide Transition via Mechanical Activation.

CHEMINFORM, Issue 5 2007
Tippawan Markmaitree
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, please click on HTML or PDF. [source]

Hydrogen Release from Mixtures of Lithium Borohydride and Lithium Amide: A Phase Diagram Study.

CHEMINFORM, Issue 28 2006
Gregory P. Meisner
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, please click on HTML or PDF. [source]

A Bis(phosphinimino)methanide Lanthanum Amide as Catalyst for the Hydroamination/Cyclization, Hydrosilylation and Sequential Hydroamination/Hydrosilylation Catalysis.

CHEMINFORM, Issue 26 2006
Marcus Rastaetter
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, please click on HTML or PDF. [source]

Conformationally Constrained ,-Amino Acid Derivatives by Intramolecular [2 + 2]-Photocycloaddition of a Tetronic Acid Amide and Subsequent Lactone Ring Opening.

CHEMINFORM, Issue 14 2006
Birte Basler
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, please click on HTML or PDF. [source]

A New Entry to Asymmetric Synthesis of Optically Active ,,,-Substituted ,-Butyrolactones, Using a Carbohydrate Derived Amide as Both a Chiral Auxiliary and a Proton Source.

CHEMINFORM, Issue 24 2005
Ling-Lin Huang
No abstract is available for this article. [source]

Highly Enantioselective Darzens Reaction of a Camphor-Derived Sulfonium Amide to Give Glycidic Amides and Their Applications in Synthesis.

CHEMINFORM, Issue 5 2003
Varinder K. Aggarwal
Abstract For Abstract see ChemInform Abstract in Full Text. [source]

ChemInform Abstract: Enantioselective ,-Alkylation of Unsaturated Carboxylic Acids Using a Chiral Lithium Amide.

CHEMINFORM, Issue 37 2001
Eva M. Brun
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]

Amide-Based Molecular Knots as Platforms for Fluorescent Switches

CHEMISTRY - A EUROPEAN JOURNAL, Issue 22 2006
Paolo Passaniti Dr.
Abstract A series of amide-based molecular knots equipped selectively with fluorescent dansyl and/or pyrenesulfonyl moieties were synthesized from the readily available tris(allyloxy)knotane. UV/Vis absorption spectra, emission spectra, and the emission lifetimes of the fluorescent knotanes were investigated in chloroform at 298 K. The absorption spectra of the knotanes correspond to those of mixtures of their UV-active constituents. The fluorescence quantum yields and lifetimes of the dansyl and pyrenesulfonyl moieties are partly quenched by the knotane platform. In the KN(Da)2(Py) species, the fluorescent excited state of the dansyl units (,max=510 nm) lies at lower energy than the fluorescent excited state of the pyrenesulfonyl unit (,max=385 nm), the emission of which is accordingly quenched with sensitization of the dansyl fluorescence. In the KN(Ao)2(Da), KN(Ao)(Da)2, and KN(Da)3 species, the addition of acids causes the protonation of their dansyl units with a consequent decrease in the intensity of the dansyl band at 510 nm and appearance of the emission band of the protonated dansyl unit (,max=340 nm). Each dansyl unit of KN(Ao)(Da)2 and KN(Da)3 undergoes the independent protonation. In these incompletely protonated knotanes the fluorescence of the protonated dansyl units is partly quenched by nonprotonated ones. These processes can be quantitatively reversed upon addition of a base. In KN(Da)2(Py), an increase of the fluorescence of its pyrenesulfonyl group is observed when the dansyl groups are protonated. The results obtained show that the readily available and easily functionalizable amide-knotanes can be used as an interesting scaffold to obtain fluorescent switches. [source]

The Mechanism of Formation of Amide-Based Interlocked Compounds: Prediction of a New Rotaxane-Forming Motif

CHEMISTRY - A EUROPEAN JOURNAL, Issue 20 2004
David A. Leigh Prof.
Abstract Molecular modeling of four different reagent systems shows that the (free) energies of supramolecular interactions in the gas phase and in solution can explain the different reaction products (i.e., various sized macrocycles, catenanes, and linear oligomers) that are formed in classic amide-catenane-forming reactions. Self-assembly of the catenanes requires the formation of ordered intertwined chains and is driven by bifurcated hydrogen bonds, with , stacking only playing a lesser role. The understanding gained from the computational study was used to predict the possibility of a new rotaxane-forming system that does not permit catenane formation. The predictions were confirmed by the successful synthesis and characterization (including X-ray crystallography) of two novel rotaxanes. [source]

Synthesis and Structure of Aminopyridinato-Stabilized Yttrium and Lanthanum Amides and Their Reactivity towards Alkylaluminium Compounds

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 3 2009
Christian Döring
Abstract A series of aminopyridinato-stabilized (amido)lanthanide complexes has been synthesized and characterized. The bulky aminopyridines (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine (1a) and [6-(2,4,6-triisopropylphenyl)pyridin-2-yl](2,4,6-trimethylphenyl)amine (1b) were introduced by amine elimination reaction with [Ln{N(SiHMe2)2}3(thf)2] (Ln = Y, La, thf = tetrahydrofuran, Me = methyl) to obtain the corresponding mono(aminopyridinato) complexes. Single-crystal X-ray analyses were carried out for the yttrium derivatives. The complexes are not able to undergo coordinative chain transfer polymerization with ethylene in the presence of alkylaluminium compounds as the corresponding dialkyl complexes do. Investigations of the reactions of the lanthanide aminopyridinato complexes with triethylaluminium or diisobutylaluminium hydride reveal a fast transfer of the aminopyridinato ligand to the aluminium atom. The products of this transfer reaction are aminopyridinato-stabilized dialkylaluminium compounds. One example of these aluminium complexes was characterized by X-ray crystal structure analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Lithium and Potassium Amides of Sterically Demanding Aminopyridines

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 16 2004
Natalie M. Scott
Abstract The reaction of Grignard compounds of 1-bromo-2,4,6-diisopropylbenzene (1) or 1-bromo-2,6-dimethylbenzene (2), formed in situ, with 2,6-dibromopyridine in the presence of a catalytic amount of [(dme)NiBr2] (dme = 1,2-dimethoxyethane) and tricyclohexylphosphane (1:2 ratio) leads to the corresponding monoarylated bromopyridines. These bromopyridines undergo Pd-catalysed aryl amination (Buchwald,Hartwig amination) with 2,6-diisopropylaniline giving rise to (2,6-diisopropylphenyl)[6-(2,4,6-triisopropylphenyl)pyridin-2-yl]amine (Ap*H) and (2,6-diisopropylphenyl)[6-(2,6-dimethylphenyl)pyridin-2-yl]amine (Ap,H) (Ap = aminopyridinate). Deprotonation of Ap*H in diethyl ether using BuLi results (after workup in hexane) in a colourless crystalline material. X-ray structural analysis reveals it to be a monomeric three-coordinate lithium aminopyridinate. In toluene solution, an equilibrium between [(Ap*Li)2] (in excess at room temperature) and [Ap*Li(OEt2)] (prominent at low temperature) is observed. Reaction of Ap,H with BuLi in diethyl ether gives rise to [Ap*LiAp*Li(OEt2)]. Deprotonation of Ap*H and Ap,H using KH leads to [Ap*K]n and [Ap,K],, respectively. [Ap,K], is a rare example of a crystalline organometallic polymer, as determined by X-ray analysis. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

A Novel Direct Conversion of Primary Amides to Their Corresponding Methyl Esters

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 6 2007
Liang-Chun Li
Abstract A novel method was used to directly convert aliphatic and aromatic primary amides into their corresponding methyl esters in high yields (up to 99,%) under mild reaction conditions. Possible mechanisms were studied at the B3LYP/6-31++G(d,p) level of theory. Formation of the ester proceeded through a rearrangement of the ,OMe and ,NH2 groups in the RC(O)NHS(O)OMe intermediate in a H+ -catalyzed six-membered ring transition state structure. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source]

Superacidic Activation of ,,,-Unsaturated Amides and Their Electrophilic Reactions

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 19 2004
Konstantin Yu.
Abstract The electrophilic reactivity of ,,,-unsaturated amides towards weak nucleophiles such as arenes and cyclohexane, initiated either with triflic acid (CF3SO3H) or with excess AlCl3, has been studied. The amides generally condense readily with aromatics in the presence of AlCl3 to give 3-arylpropionamides and related compounds in excellent yields, while some amides also undergo selective ionic hydrogenation with cyclohexane to give saturated amides. The proposed mechanism of these reactions involves dicationic intermediates (superelectrophiles). The direct observation of a dicationic species (by low-temperature NMR) is reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source]

Cyclopeptides and Amides from Pseudostellaria heterophylla (Caryophyllaceae)

HELVETICA CHIMICA ACTA, Issue 10 2003
Ya-bin Yang
From the roots of Pseudostellaria heterophylla, three cyclopeptides and three amides were isolated, besides heterophyllin A and B. Their structures were determined as cyclo (Ala-Gly-Pro-Val-Tyr-) (heterophyllin J; 1), cyclo (Ala-Gly-Pro-Tyr-Leu-) (pseudostellarin A; 2), cyclo (Gly-Gly-Gly-Pro-Pro-Phe-Gly-Ile-) (pseudostellarin B; 3), methyl , -hydroxypyroglutamate (4), methyl pyroglutamate (5), and pyroglutamic acid (6) on the basis of spectral data, especially 2D-NMR data. Among them, compounds 1 and 4 are new compounds. [source]

Selective Hydrogenation of Amides using Ruthenium/ Molybdenum Catalysts

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2010
Graham Beamson
Abstract Recyclable, heterogeneous bimetallic ruthenium/molybdenum catalysts, formed in situ from triruthenium dodecacarbonyl [Ru3(CO)12] and molybdenum hexacarbonyl [Mo(CO)6], are effective for the selective liquid phase hydrogenation of cyclohexylcarboxamide (CyCONH2) to cyclohexanemethylamine (CyCH2NH2), with no secondary or tertiary amine by-product formation. Variation of Mo:Ru composition reveals both synergistic and poisoning effects, with the optimum combination of conversion and selectivity at ca. 0.5, and total inhibition of catalysis evident at ,1. Good amide conversions are noted within the reaction condition regimes 20,100,bar hydrogen and 145,160,°C. The order of reactivity of these catalysts towards reduction of different amide functional groups is primary>tertiary,secondary. In situ HP-FT-IR spectroscopy confirms that catalyst genesis occurs during an induction period associated with decomposition of the organometallic precursors. Ex situ characterisation, using XRD, XPS and EDX-STEM, for active Mo:Ru compositions, has provided evidence for intimately mixed ca. 2.5,4,nm particles that contain metallic ruthenium, and molybdenum (in several oxidation states, including zero). [source]

Palladium-Catalyzed One-Pot Conversion of Aldehydes to Amides

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010
Md Ashif Ali
Abstract The palladium-catalyzed one-pot conversion of aldehydes into primary amides in the presence of hydroxylamine hydrochloride in aqueous dimethyl sulfoxide (DMSO) at moderate temperature is described. The process is selective and free from the addition of an external chelating ligand. [source]