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Eiichi Nakamura

Publications and source records attributed to Eiichi Nakamura.

At least 19 recordsLinked to original sources
PubMed2006

Aminohydroxyphosphine ligand for the copper-catalyzed enantioselective conjugate addition of organozinc reagents.

An alanine-derived aminohydroxyphosphine ligand was developed for copper-catalyzed asymmetric conjugate addition of organozinc reagents to alpha,beta-unsaturated carbonyl compounds. This new tridentate ligand induces consistently high enantioselectivity in reactions of a variety of acyclic substrates. Theoretical mechanistic analysis suggests that the C-C bond formation takes place through a highly ordered transition state by the coordination of the phosphorus and nitrogen atoms to the copper(III) and zinc(II) atoms, respectively, and of the oxygen anion to both the metal centers.

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PubMed2006

Synthesis and structural, electrochemical, and stacking properties of conical molecules possessing buckyferrocene on the apex.

A series of conical molecules featuring a [60]fullerene/ferrocene hybrid and five aralkyl side chains (Fe[C60{C6H4-(OCO-C6H3-(OR)2-3,4)-4}5]Cp) have been synthesized and examined for their structural and electrochemical properties as well as their ability to form supramolecular structures in crystals and liquid crystals. When the R group on the side is a methyl group, the compound forms crystals in which the dipolar conical molecules are stacked head-to-tail to form a columnar structure. When the R group is as long as a C18H38 group, the compound forms liquid crystals. Oxidation of the liquid crystalline compound by an aminium salt [(4-BrC6H4)3N][SbCl6] produces the corresponding paramagnetic Fe(III) compound that also exhibits liquid crystalline properties.

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PubMed2006

Sharing orbitals: ultrafast excited state deactivations with different outcomes in bucky ferrocenes and ruthenocenes.

We report on the singlet ground and singlet/triplet excited-state features of a series of bucky ferrocenes, bucky ruthenocenes, and respective reference compounds. In the bucky ferrocene conjugates, intimate contacts between the fullerenes and ferrocenes result in appreciable ground-state interactions-suggesting a substantial shift of charge density from the electron donor (i.e., ferrocene) to the electron acceptor (i.e., fullerene). In contrast, no prominent charge-transfer features were observed for the bucky ruthenocene conjugates. An arsenal of experimental techniques, ranging from fluorescence (i.e., steady state and time-resolved) and pump probe experiments (i.e., femtosecond and nanoseconds) to pulse radiolysis, were employed to examine excited-state interactions. In the excited states, bucky ferrocene conjugates are dominated by rapid charge separation reactions (0.8 +/- 0.1 ps) to yield metastable radical ion pairs. The radical ion pair lifetimes vary between 27 and 39 ps. No charge separation was, however, found in the corresponding bucky ruthenocence. Instead, an intrinsically faster excited-state deactivation (approximately 200 ps) evolves from the heavier ruthenium center-relative to iron. This effect is further augmented by the unfavorably shifted oxidation potential in ruthenocene of about 0.61 V, which in ruthenocene (-deltaG(ET) = -0.26 eV), in contrast to ferrocene (-deltaG(ET) = 0.35 eV), renders charge separation thermodynamically unfeasible.

Journal Article↗
PubMed2006

Role of steroid administration to reduce inflammation after thoracotomy in a rat surgical stress model.

BACKGROUND: Unilateral lung surgical insult can lead to bilateral pulmonary inflammation after transthoracic esophagectomy for esophageal cancer. An inflammatory response of the cytokine network induced by surgical stress followed by neutrophil sequestration is the major mechanism involved in these complications. We examined modulation of the inflammatory cytokine and neutrophil sequestration by preoperative steroid administration in a rat thoracotomy model. METHODS: Adult male rats were subjected to right thoracotomy with pulmonary compression in the surgical stress model. In the another surgical stress model, 10 mg/kg of methylprednisolone (MP) was administered 1 h before the operation intraperitoneally, and peri-operative biological effects of steroid administration to neutrophil sequestration and cytokine-induced neutrophil chemoattractant (CINC) as an inflammatory cytokine were examined. Sham-operated animals were subjected to intubation only. RESULTS: Surgical insult to the unilateral lung increased local CINC concentration followed by an increase in neutrophil sequestration, wet-to-dry weight ratio in bilateral lungs and systemic CINC concentration. Pre-treatment with methylprednisolone reduced CINC concentration as well as neutrophil sequestration and wet-to-dry weight ratio of both lungs. CONCLUSIONS: These data suggest that inflammatory changes induced by the unilateral operative procedure occur in both lungs through local inflammatory response. Pre-operative methylprednisolone administration down-regulates cytokine release and neutrophil sequestration, preventing lung edema, and possibly may act as a prophylactic treatment against acute lung injury caused by a so-called "second attack" theory.

Animals↗
PubMed2006

Synthesis and electrochemistry of double-decker buckyferrocenes.

D5d- and C5v-symmetric double-decker buckyferrocene Fe2(C60R10)Cp2 (R10 = Me5Ph5 and Me10) represents a new type of diiron complexes featuring conjugative connection of two ferrocene groups by a hoop-shaped [10]cyclophenacene. The compounds exhibit two-electron oxidation and two-electron reduction behavior, generating dicationic and dianionic species. The two iron atoms interact with each other through the pi-conjugation of the cyclophenacene, as revealed by differential pulse voltammetric analysis of the D5d Fe2(C60Me10)Cp2.

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PubMed2006

Convergent synthesis of a polyfunctionalized fullerene by regioselective five-fold addition of a functionalized organocopper reagent to C60.

[reaction: see text] A method for one-step preparation of polyfunctionalized fullerene derivatives by regioselective penta-addition of an organocopper reagent is described. A functionalized aryl iodide is first converted to the corresponding Grignard reagent and then to a copper reagent and finally is allowed to react with C(60). The method allows introduction of five functional groups to the C(60) skeleton in a convergent manner. The shuttlecock-like molecules crystallize into a columnar packing structure.

Journal Article↗
PubMed2006

Synthesis of ultrafine Gd2O3 nanoparticles inside single-wall carbon nanohorns.

The large diameter of single-wall carbon nanohorns (SWNHs) allows various molecules to be easily incorporated in hollow nanospaces. In this report, we prove that the nanospaces of SWNHs even work as the chemical reaction field at high temperature; that is, Gd-acetate clusters inside SWNHs were transformed into ultrafine Gd(2)O(3) nanoparticles with their particle size retained even after heat-treatment at 700 degrees C. This indicates that the confinement of the Gd-acetate clusters in a deep potential well of the SWNH nanospaces prevented a migration to form larger particles, giving rise to ultrafine Gd(2)O(3) nanoparticles of 2.3 nm in average diameter, which is much smaller than the case without SWNHs. The Gd(2)O(3) nanoparticles thus obtained were demonstrated to be actually useful to the magnetic resonance imaging. We believe that the presented effectiveness of the inner hollow spaces of SWNHs, therefore, also those of the carbon nanotubes, for high-temperature chemical reactions should be highlighted, and that the thus produced novel nanomaterials are promising to expand the fields of nanoscience.

Letter↗
PubMed2005

Nickel-catalyzed cross-coupling reaction of aryl fluorides and chlorides with grignard reagents under nickel/magnesium bimetallic cooperation.

Nickel-catalyzed cross-coupling of Grignard reagents with aryl (poly)fluorides or (poly)chlorides can be achieved efficiently in the presence of a new triarylphosphine ligand bearing a nearby hydroxy group. The high reactivity and the unique chemoselectivity (ArF > ArOTf > ArSR) of the catalysis have been attributed to synergy of nickel and magnesium atoms preorganized on the ligand, as has been surmised on the basis of theoretical modeling of the reaction mechanism.

Journal Article↗
PubMed2005

Organic and organometallic derivatives of dihydrogen-encapsulated [60]fullerene.

Regioselective multi-addition reaction of organocopper and amine compounds onto dihydrogen-encapsulated [60]fullerene, H2@C60, produced a variety of organic and organometallic derivatives of H2@C60. The X-ray crystallographic analysis of dihydrogen-encapsulated bucky ferrocene, Fe(H2@C60Ph5)C5H5, showed the presence of the dihydrogen molecule located almost in the center but slightly away from the ferrocene moiety. The 1H NMR chemical shift values for the encapsulated molecular hydrogen indicated that these values are susceptible to the magnetic environment of the inside as well as the outside of the fullerene cage.

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PubMed2005

Synthesis of hydrophosphorylated fullerene under neutral conditions.

[chemical reaction: see text]. A variety of phosphorous compounds such as secondary phosphines, phosphine oxides, phosphinates, and phosphonates undergo addition to [60]fullerene in DMSO/C6H5Cl without extraneous reagents to produce hydrophosphorylated fullerene derivatives in moderate to high yield.

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PubMed2005

Fractal behavior of functionalized fullerene aggregates. I. Aggregation of two-handed tetraaminofullerene with DNA.

In tris-buffered saline (TBS) with a trace of dimethylformamide (DMF), the homoaggregation process of a functionalized fullerene, the two-handed tetraaminofullerene (TH), and the heteroaggregation process (complex formation) of TH with DNA (pGL3-control plasmid) were studied dynamically by using a combination of static and dynamic laser light scattering measurements. Fractal behavior was investigated in the aggregation process of both TH homoaggregates and TH-DNA heteroaggregates. The stability of aggregates in solution depends on the molar concentration ratio R(M), defined as the molar ratio of moles of TH to moles of the DNA base pair. Higher R(M) values resulted in lower aggregate stability. The transition of the fractal dimension (Df) in TH homoaggregation by rapidly mixing 3.78 microM TH with an equal volume of the blank buffer was found to vary from a value of 1.46 to 2.02. Dynamic light scattering results revealed that, in the aggregation process, the change in the size distribution of aggregates with time could be related to a Df transition. In the Df transition region, the size distribution of homoaggregates displayed a drastic change from a single-mode distribution to a bimodal distribution, which clearly suggested a restructuring process with the formation of large aggregates. When the aggregation process finally reached equilibrium, Df = 2.02, the size of the homoaggregates had a single mode but a broad distribution. However, TH-DNA heteroaggregation showed a Df transition from 1.58 to 1.7, but over a shorter time range of less than 5 min. Then, the Df value fluctuated in the range of 1.7 and finally reached an equilibrium value of Df approximately 1.78, which was independent of molar concentration. There are two main action forces involved in the heteroaggregation process: van der Waals forces and attractive electrostatic forces, with the latter one being stronger and faster than that of the former. Therefore, a two-step action could occur in the heteroaggregation process. In the beginning of mixing, the attractive electrostatic forces dictated the aggregation process, and then van der Waals forces also got involved in the entire aggregation process. By using an initial concentration of 3.78 microM each and R(M) = 1, TH-DNA heteroaggregates showed more stable solution behavior than the homoaggregates. The lower Df value of the heteroaggregates could be related to a looser compact structure. Results from scanning electron microscopy (SEM) also disclosed the different textures between TH homoaggregates and TH-DNA heteroaggregates; the former had a more dense packing than the latter one.

DNA↗
PubMed2005

Alkylation of magnesium enamide with alkyl chlorides and fluorides.

A magnesium enamide derived from N-2-(N',N'-diethylamino)ethyl imine reacts with a primary and secondary alkyl chloride or a primary alkyl fluoride to give an alpha-alkylated ketone in good to excellent yield after hydrolysis. The reaction takes place with a high level of inversion of stereochemistry at the electrophilic carbon center and will be useful for production of optically active compounds.

Alkylation↗
PubMed2005

Controlling the incorporation and release of C60 in nanometer-scale hollow spaces inside single-wall carbon nanohorns.

We succeeded in large-scale preparation of single-wall carbon nanohorns (SWNH) encapsulating C60 molecules in a liquid phase at room temperature using a "nano-precipitation" method, that is, complete evaporation of the toluene from a C60-SWNH-toluene mixture. The C60 molecules were found to occupy 6-36% of the hollow space inside the SWNH, depending on the initial quantity of C60. We showed that the C60 in C60@SWNHox was quickly released in toluene, and the release rate decreased by adding ethanol to toluene. Numerical analysis of the release profiles indicated that there were fast and slow release processes. We consider that the incorporation quantity and the release rate of C60 were controllable in/from SWNHs because SWNHs have large diameters, 2-5 nm.

Journal Article↗
PubMed2005

Mössbauer spectroscopy of bucky ferrocenes: lattice dynamics and motional anisotropy of the metal atom.

Temperature-dependent (57)Fe Mössbauer effect spectroscopy has been used to elucidate the metal atom dynamics in three neutral and two cationic bucky ferrocenes. For the three diamagnetic complexes Fe(C(60)H(5))Cp (1), Fe(C(60)Me(5))Cp (2), and Fe(C(60)Ph(5))Cp (3), the metal atom motion is anisotropic and the temperature dependence of the mean-square amplitude of vibration of the metal atom at a number of temperatures is reported. The Mössbauer lattice temperatures have been determined and compared to the parent ferrocene (6). The synthesis and X-ray crystal structure of 3 have been determined at 153(2) K, and the (1)H and (13)C NMR spectra have been recorded. The cationic complexes derived from 2 and 3 show spin-lattice relaxation. The relaxation rate appears insensitive to the nearest-neighbor environment of the metal atom in this pair.

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