Showing papers on "Reactivity (chemistry) published in 2006"
TL;DR: In this article, a number of functionalized graphite oxides were prepared by treatment of graphite oxide (GO) with organic isocyanates, which can then be exfoliated into functionalized graphene oxide nanoplatelets that can form a stable dispersion in polar aprotic solvents.
2,103 citations
TL;DR: Experimental and computational evidence indicates that the pivalate anion is a key component in the palladium-pivalic acid cocatalyst system, that it lowers the energy of C-H bond cleavage and acts as a catalytic proton shuttle from benzene to the stoichiometric carbonate base.
Abstract: A palladium−pivalic acid cocatalyst system has been developed that exhibits unprecedented reactivity in direct arylation This reactivity is illustrated with the first examples of high yielding direct metalation−arylation reactions of a completely unactivated arene, benzene Experimental and computational evidence indicates that the pivalate anion is a key component in the palladation/C−H bond breaking event, that it lowers the energy of C−H bond cleavage and acts as a catalytic proton shuttle from benzene to the stoichiometric carbonate base Eight examples of substituted aryl bromides are included which undergo direct arylation with benzene in 55−85% yield
839 citations
TL;DR: In this article, nitrogen-doped carbon nanotubes (N-CNTs) were used to assess quantitatively the compositional and structural properties of the N-Notubes and Raman microscopy analysis indicated a shift in and broadening of the C 1s spectra track with increasing disorder induced by selective nitrogen doping.
665 citations
TL;DR: The obtained results suggest a surface initiated reaction involving Msurf2+ (Fe, Co or Mn), producing HO radicals, which can lead to two competitive reactions, i.e. the decomposition of H2O2 or the oxidation of organics present in the aqueous medium.
438 citations
TL;DR: It is reported that reductive cleavage of the boron-bromine bond in N,N′-bis(2,6-diisopropylphenyl)-2- bromo-2,3-dihydro-1H-1,3,2-diazaborole by lithium naphthalenide afforded the corresponding boryllithium, which is isoelectronic with an N-heterocyclic carbene.
Abstract: Nucleophilic, anionic boryl compounds are long-sought but elusive species. We report that reductive cleavage of the boron-bromine bond in N,N ′-bis(2,6-diisopropylphenyl)-2-bromo-2,3-dihydro-1 H -1,3,2-diazaborole by lithium naphthalenide afforded the corresponding boryllithium, which is isoelectronic with an N -heterocyclic carbene. The structure of the boryllithium determined by x-ray crystallography was consistent with sp 2 boron hybridization and revealed a boron-lithium bond length of 2.291 ± 0.006 angstroms. The structural similarity between this compound and the calculated free boryl anion suggests that the boron atom has an anionic charge. The 11 B nuclear magnetic resonance spectrum also supports the boryl anion character. Moreover, the compound behaves as an efficient base and nucleophile in its reactions with electrophiles such as water, methyl trifluoromethanesulfonate, 1-chlorobutane, and benzaldehyde.
438 citations
TL;DR: This article showed that the initial structure alone alone does not dictate the reactivity of diesel soot and rather the initial oxygen groups have a strong influence on the oxidation rate, leading to the formation of graphene ribbon structures.
409 citations
TL;DR: In this paper, transition metal nanoclusters are used for the hydrogenation of nitrobenzene and showed excellent reactivity, with a conversion rate that was ∼5 times higher than commercial Pd/C catalyst.
Abstract: Transition metal nanoclusters are highly selective and active catalysts. To allow for ease of recycling, Pd nanoclusters were supported on SiO2/Fe2O3 magnetic nanocomposites. Pd/HS-SiO2/Fe2O3 and Pd/H2N-SiO2/Fe2O3 were examined for the hydrogenation of nitrobenzene. Pd/H2N-SiO2/Fe2O3 showed excellent reactivity, with a conversion rate that was ∼5 times higher than commercial Pd/C catalyst.
354 citations
TL;DR: A new and readily available bidentate ligand, namely, pyrrolidine-2-phosphonic acid phenyl monoester (PPAPM), has been developed for the copper-catalyzed formation of C-N, C-O, and P-C bonds, and various N-arylation products were synthesized by using the CuI/ PPAPM catalyst system.
Abstract: A new and readily available bidentate ligand, namely, pyrrolidine-2-phosphonic acid phenyl monoester (PPAPM), has been developed for the copper-catalyzed formation of C-N, C-O, and P-C bonds, and various N-, O-, and P-arylation products were synthesized in good to excellent yields by using the CuI/PPAPM catalyst system. Addition of the PPAPM ligand greatly increases the reactivity of the copper catalyst, and the resulting versatile and efficient catalyst system is of widespread and practical application in cross-coupling reactions.
337 citations
TL;DR: The synthesis of a novel divalent silicon compound by debromination of the corresponding dibromosilyl precursor is reported, and addition of Me3SiX to the silylene furnishes the corresponding 1,4-adduct which subsequently rearranges to the thermodynamically favored 1,1- adduct.
Abstract: The synthesis of a novel divalent silicon compound by debromination of the corresponding dibromosilyl precursor is reported. The silylene possesses a unique reactivity toward electrophiles of the type R−X (R = H, silyl; X = halogen, triflate) in comparison with the germanium congener. DFT calculations suggest that this is due to a much higher basicity of the silylene versus that of germylene lone-pair electrons. Thus, addition of Me3SiX to the silylene (X = OSO2CF3, triflate) furnishes the corresponding (kinetically favored) 1,4-adduct which subsequently rearranges to the thermodynamically favored 1,1-adduct.
300 citations
TL;DR: The reactivity studies on nitrate reduction showed that the freshly synthesized iron reacted at the fastest rate, and the reduction rate of the second cycle was the fastest among the six cycles, which can be attributed to the increase of surface area and the fresh iron surfaces that were bared by the dissolution of oxidized iron species on the surface.
Abstract: The pyrophoric character of zerovalent iron nanoparticles and cumbersome handling of this material has been a drawback in practical applications, despite the expectation of an enhanced reactivity. We have been interested in how the iron nanoparticles can gain stability in air without significantly sacrificing reactivity. The freshly synthesized iron nanoparticles ignited spontaneously upon exposure to air. However, when exposed slowly to air, an approximately 5 nm coating of iron oxide was formed on the surface of particles. The oxide shell did not thicken for at least two months, indicating no sign of further corrosion of iron particles. The reactivity studies on nitrate reduction showed that the freshly synthesized iron reacted at the fastest rate. After formation of the oxide shell the rate constants decreased by ca. 50% of that of fresh iron, but were still higher than that of commercial grade micro- or milli-sized iron powder. Nitrate (50 ppm/350 mL) can be recharged 6 times into a bottle containing 0.5 g of iron nanoparticles. The reduction rate of the second cycle was the fastest among the six cycles, which can be attributed to the increase of surface area and the fresh iron surfaces that were bared by the dissolution of oxidized iron species on the surface. The oxidized iron was transformed to crystalline magnetite (Fe3O4) in solution.
272 citations
TL;DR: Palladium-catalyzed ligand directed C-H activation/halogenation reactions have been extensively explored in this paper, where both the nature of the directing group and the substitution pattern on the arene ring of the substrate lead to different reactivity profiles, and often different and complementary products, in the presence and absence of the catalyst.
TL;DR: It is demonstrated that additions of amines to vinylarenes and dienes occur in the presence of potentially reactive functional groups, such as ketones with enolizable hydrogens, free alcohols, free carboxylic acids, free amides, nitriles, and esters.
Abstract: We report a catalyst for intermolecular hydroamination of vinylarenes that is substantially more active for this process than catalysts published previously. With this more reactive catalyst, we demonstrate that additions of amines to vinylarenes and dienes occur in the presence of potentially reactive functional groups, such as ketones with enolizable hydrogens, free alcohols, free carboxylic acids, free amides, nitriles, and esters. The catalyst for these reactions is generated from [Pd(η3-allyl)Cl]2 (with or without added AgOTf) or [Pd(CH3CN)4](BF4)2 and Xantphos (9,9-dimethyl-4,5-bis(diphenylphosphino)xanthene), which generates complexes with large P−Pd−P bite angles. Studies on the rate of the C−N bond-forming step that occurs by attack of amine on an η3-phenethyl and an η3-allyl complex were conducted to determine the effect of the bite angle on the rate of this nucleophilic attack. Studies on model η3-benzyl complexes containing various bisphosphines showed that the nucleophilic attack was faster f...
TL;DR: Results of spectroscopic experiments clarified that this enhanced reactivity can be attributed to the intramolecular hydroge...
Abstract: A thiourea-catalyzed asymmetric Michael addition of activated methylene compounds to α,β-unsaturated imides derived from 2-pyrrolidinone and 2-methoxybenzamide has been developed. In the case of 2-pyrrolidinone derivatives, the reaction with malononitrile proceeded in toluene with high enantioselectivity, providing the Michael adducts in good yields. However, the nucleophiles that could be used for this reaction were limited to malononitrile due to poor reactivity of the substrate. Further examination revealed that N-alkenoyl-2-methoxybenzamide was the best substrate among the corresponding benzamide derivatives bearing different substituents on the aromatic ring. Indeed, several activated methylene compounds such as malononitrile, methyl α-cyanoacetate, and nitromethane could be employed as a nucleophile to give the Michael adducts in good to excellent yields with up to 93% ee. The results of spectroscopic experiments clarified that this enhanced reactivity can be attributed to the intramolecular hydroge...
TL;DR: In this paper, Li0.45(Ni0.8Co0.15Al0.05)O2 and Li 0.55(Ni1/3Co 1/3Mn 1/5Mn1/5 )O2 powders were delithiated using NO2BF4 oxidizer in an acetonitrile medium.
TL;DR: In this paper, the authors measured the surface reactivity of 7-nm hematite nanoparticles with average diameters of 7nm, 25-nm and 88-nm in 0.1-M NaNO3.
TL;DR: Critical to the success of the synthesis and isolation was the decision to generate 1 by a route other than classical amide bond formation, and it is anticipated that these results will provide a greater understanding of the properties of amide bonds.
Abstract: The amide functional group is one of the most fundamental motifs found in chemistry and biology, and it has been studied extensively for the past century. Typical acyclic amides are planar. But the amide groups of bicyclic bridgehead lactams are highly twisted, and this distortion from planarity can dramatically affect the stability and reactivity of these amides; it also increases the basicity of the nitrogen so that it often behaves more like an amine than a typical planar amide. As a result, the structures and reactivity profiles of these 'anti-Bredt' amides differ significantly from those of planar amides. It is possible that this twisting phenomenon is not exclusive to cyclic systems—non-planarity may also be a critical biological design element that leads to amide ground-state destabilization and alters the reactivity, selectivity and mechanism of various protein and enzymatic processes (such as amide hydrolysis). The intriguing qualities of these twisted amides were first recognized in 1938 (ref. 11), wherein one of the simplest families was introduced—molecules containing the 1-azabicyclo[2.2.2]octan-2-one system. But the parent member of this group, 2-quinuclidone (molecule 1 in this paper), has not yet been unambiguously synthesized. Here, we report the chemical synthesis, isolation and full characterization of the HBF_4 salt of 1. Critical to the success of the synthesis and isolation was the decision to generate 1 by a route other than classical amide bond formation. We anticipate that these results will provide a greater understanding of the properties of amide bonds.
TL;DR: The use of carbon-centered nucleophiles is much less developed, yet represents a significant advance since it builds the basic carbon framework as mentioned in this paper, and offers the possibility of generating valuable, chiral, nonracemic building blocks in a very simple, stereodefined manner.
TL;DR: The efficiencies of corrosion inhibitors and the global chemical reactivity relate to some parameters, such as EHOMO, ELUMO, gap energy (ΔE) and other parameters, including electronegativity (χ), global hardness (η) and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (N).
Abstract: In the present work, a theoretical study of five bipyrazolic-type organic compounds, 4-{bis[(3,5-dimethyl-1H-pyrazolyl-1-yl)methyl]-amino}phenol (1), N1,N1-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl}]-N4,N4-dimethyl-1,4-benzenediamine (2), N,N-bis[(3,5-dimethyl-1H-pyrazol-1-yl)methyl]aniline (3), 4-[bis(3,5-dimethyl pyrazol-1-yl-methyl)-amino]butan-1-ol (4) and ethyl4-[bis(3,5-dimethyl-1H-pyrazol-1-yl-methyl) aminobenzoate] (5), has been performed using density functional theory (DFT) at the B3LYP/6-31G(d) level in order to elucidate the different inhibition efficiencies and reactive sites of these compounds as corrosion inhibitors. The efficiencies of corrosion inhibitors and the global chemical reactivity relate to some parameters, such as EHOMO, ELUMO, gap energy (DeltaE) and other parameters, including electronegativity (chi), global hardness (eta) and the fraction of electrons transferred from the inhibitor molecule to the metallic atom (DeltaN). The calculated results are in agreement with the experimental data on the whole. In addition, the local reactivity has been analyzed through the Fukui function and condensed softness indices.
TL;DR: Three fundamentally important reactions of the [(((R)ArO)3tacn)U]-system are presented that result in alkane coordination, CO/CO2 activation, and nitrogen atom-transfer chemistry.
TL;DR: A novel asymmetric Friedel-Crafts alkylation of indoles with nitroalkenes catalyzed by Zn(II)-bisoxazoline complexes has been developed and is synthesized in excellent yields and high enantioselectivities.
Abstract: A novel asymmetric Friedel−Crafts alkylation of indoles with nitroalkenes catalyzed by Zn(II)−bisoxazoline complexes has been developed. The nitroalkylated indoles are synthesized in excellent yields and high enantioselectivities (up to 90% ee). The effects of ligand structure, metal salt, and solvent on the reaction are discussed. The substrates of the reaction can be aromatic, heteroaromatic, and even aliphatic nitroalkenes. The high reactivity and selectivity of the reaction are presumptively attributed to the activation and asymmetric induction of chiral Lewis acids coordinated by nitroalkene substrates through a 1,3-metal bonding model.
TL;DR: The first example of a complex which possesses a retrodative (i.e., metal-to-ligand) Fe→B bond was obtained via reaction of the tris(2-mercapto-1-tert-butylimidazolyl)hydroborato complex [TmBut]FeCl with LiCH2SiMe3 followed by treatment with CO.
Abstract: The ferraboratrane [κ4-B(mimBut)3]Fe(CO)2 (mimBut = 2-mercapto-1-tert-butylimidazolyl), the first example of a complex which possesses a retrodative (i.e., metal-to-ligand) Fe→B bond, is obtained via reaction of the tris(2-mercapto-1-tert-butylimidazolyl)hydroborato complex [TmBut]FeCl with LiCH2SiMe3 followed by treatment with CO. Significantly, [κ4-B(mimBut)3]Fe(CO)2 exhibits novel reactivity towards a variety of reagents that results in eradication of the Fe→B bond via a formal 1,2-addition process and the formation of B-functionalized tris(mercaptoimidazolyl)borate derivatives, [XTmBut]FeY.
13 Jun 2006
TL;DR: In this article, a solid state strategy for the preparation of carbon-rich polymers is presented. Butadi et al. present a synthesis and chemistry of Polycyclic Aromatic Hydrocarbons with Curved Surfaces: Buckybowls.
Abstract: Foreword.Preface.List of Contributors.1. Pioneers of Carbon-rich Compounds.2. Electronic Conduction in Photoactive Metallo-wires.3. All-benzenoid Polycyclic Aromatic Hydrocarbons: Synthesis, Self-assembly and Applications in Organic Electronics.4. [N]Phenylenes: a Novel Class of Cyclohexatrienoid Hydrocarbons.5. A Solid State Strategy for the Preparation of Carbon-rich Polymers.6. Chiral Carbon-rich Macrocycles and Cyclophanes.7. Carbon-rich Cycles with Two and More 1,3-Butadiyne Units ? Syntheses, Structures and Reactivities.8. Carbon-rich Structures: Computational Considerations.9. Fullerene Reactivity - Fullerene Cations and Open-Cage Fullerenes.10. Polyynes.11. Defined-length Carbon-rich Conjugated Oligomers.12. Synthesis and Chemistry of Polycyclic Aromatic Hydrocarbons with Curved Surfaces: Buckybowls.13. Reduction of Carbon-rich Compounds.Index.
TL;DR: The strong Lewis acid tris(pentafluorophenyl)boron, B(C6F5)3, reacts with several nitrogen-containing Lewis bases (nitriles, amines, imines, pyridines, etc.) and also with non-basic substrates (such as pyrroles and indoles) producing in both cases the B N coordination adduct as mentioned in this paper.
TL;DR: In this paper, a series of bisNHC chelate ligands with alkyl bridges of different chain lengths and their palladium complexes have been prepared, and the influence of the different bridges on the solid-state structure and reactivity of the complexes has been studied.
TL;DR: It is shown here that La@C72 has a non-IPR cage, unique electronic properties, and high reactivity by the spectroscopic and X-ray crystallographic analysis and the theoretical study.
Abstract: We show here that La@C72 has a non-IPR cage, unique electronic properties, and high reactivity by the spectroscopic and X-ray crystallographic analysis and the theoretical study. The isolation of La@C72 as a stable derivative might constitute an important stepping-stone on the way to isolation of these unknown metallofullerenes and open new material science of metallofullerenes.
TL;DR: The in situ preparation and isolation of surface methoxy species on acidic zeolites are followed by further investigations of their reactivity in heterogeneously catalyzed reactions, and solid-state NMR evidence for the high reactivity of surface methamphetamine species has been obtained.
Abstract: The in situ preparation and isolation of surface methoxy species on acidic zeolites are followed by further investigations of their reactivity in heterogeneously catalyzed reactions. For the first time, the following solid-state NMR evidence for the high reactivity of surface methoxy species has been obtained: (i) Surface methoxy species react readily with ammonia on acidic zeolites at room temperature, by which methylamines and methylammonium cations are formed. (ii) The transformation of surface methoxy species to other alkoxy species can be achieved by the reaction of surface methoxy species and corresponding alkyl halides on acidic zeolites. (iii) Surface methoxy species react readily with hydrochloride, giving methyl chloride as the sole product. (iv) The classic Koch carbonylation reaction and Ritter reaction in solution can be performed with surface methoxy species on acidic zeolites. (v) Carbon monoxide and carbon dioxide are produced by the oxidation of surface methoxy species in the presence of...
TL;DR: In this paper, a microreview outlines recent advances in the area of asymmetric NDA reaction following the review by Streith and Defoin in 1994, and a number of important compounds have been synthesized using this method.
TL;DR: The 1H and 31P NMR studies of the reaction of Ru(CO)(PPh3)3 with o-aryloxy pivalophenone revealed that the C-H bond cleavage is a kinetically favorable process but theC-O bond cleaving is a thermodynamic one.
Abstract: When RuH2(CO)(PPh3)3 was reacted with 2,2-dimethyl-1-(2-p-tolylphenyl)propan-1-one (2), the ruthenium-aryloxy complex 3 was obtained in 76% yield. The structure of this complex was determined from 1H and 31P NMR and X-ray data. Complex 3 showed the catalytic activity for the coupling of 2 with the phenylboronate 4. The 1H and 31P NMR studies of the reaction of Ru(CO)(PPh3)3 with o-aryloxy pivalophenone revealed that the C-H bond cleavage is a kinetically favorable process but the C-O bond cleavage is a thermodynamic one. The reaction of 2'-methoxyacetophenone with vinylsilane and organoboronate resulted in chemoselective C-C bond formation.
TL;DR: In this paper, 2-mercapto-1-methylimidazole was investigated by dc polarization, ac impedance and weight loss techniques, and a significant decrease in the corrosion rate of copper was observed in the presence of the investigated compound.