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The biocompatibility and osteoconductivity of metallic biomaterials can be achieved by calcium phosphate (CaP) coating. We recently developed a laser-assisted biomimetic (LAB) process for rapid and area-specific CaP coating on several materials. In the present study, the LAB process was applied to cobalt&ndash, chromium (Co&minus, Cr) alloy, a metallic biomaterial widely used in orthopedic and dental applications. The LAB process was conducted by irradiation of unfocused pulsed laser light onto the substrate immersed in supersaturated CaP solution. The LAB-processed substrate formed CaP on the irradiated surface within only 5 min and was coated with a micron-thick CaP layer within 30 min by the effects of laser-induced surface modification and heating. Ultrastructural analysis with transmission electron microscopy revealed that the resultant CaP layer was integrated with the underlying substrate through two intermediate layers, an upper chromium oxide layer and a lower Co-rich (Cr-deficient) alloy layer. The CaP layer was loaded with a large number of cobalt chromite (CoCr2O4) nanoparticles. The results obtained offer new insights into the mechanism of CaP coating in the LAB process and future applications of LAB-processed Co&minus, Cr alloys.

Background: Crystalline silica is an important cause of serious pulmonary diseases. The relationship between this hazard and various physicochemical parameters of crystalline silica has been studied for more than a century, and the toxic potential of silica is known to be associated with its surface properties. However, no in vivo dataset has yet been accumulated to clarify the relevance of this, especially regarding longer term effects. To provide new insights into these longer term effects, we performed single intratracheal instillation testing of five different crystalline silicas and assessed the time-course changes in pulmonary inflammation, lung burden, and thoracic lymph node loads. The tested silicas were prepared from two commercial products [Min-U-Sil5 (MS5, US Silica Company) and SIO07PB (SPB, Kojundo Chemical)] by using three different pretreatment steps: centrifugation (C), grinding (G), and surface dissolving (D). The five types of silica particles—MS5, MS5_C, SPB_C, SPB_G, and SPB_D—were suspended in purified water and intratracheally instilled into male F344 rats. Bronchoalveolar lavage, lung burden analysis, and histopathological examination were performed 3, 28, and 91 days after instillation.Results: MS5 and MS5_C provoked similar biphasic inflammation that differed in severity: MS5 induced granuloma generation 91 days after instillation, whereas the smaller particles of MS5_C elicited only macrophage aggregation. SPB_C induced severe and persistent inflammation, whereas SPB_G and SPB_D induced only slight and transient acute inflammation. All of the silicas were dose-dependently retained in the lung. Silicas that induced prolonged responses were translocated to the thoracic lymph nodes as early as 28 days after instillation. Those that induced transient inflammation were removed effectively from the lung with very little lymph node retention. No quantitative association was identified between lung retention and physicochemical properties, although common features of the retained materials seemed to be reduced solubility, similar surface properties, and relatively small particle. Conclusion: Our key findings suggest that prolonged silica toxicity occurs through lymph node retention. Although the main drivers of translocation to the lymph nodes have not yet been clarified, we provide in vivo evidence of the contributions of at least silica solubility, surface properties, and particle size.

A technique for implementing biocompatible and antibacterial functions to a targeted region on tooth surfaces has potential in dental treatments. We have recently demonstrated pseudo-biomineralization, i.e., the growth of an apatite layer on a human dentin substrate by a laser-assisted biomimetic (LAB) process, based on pulsed laser irradiation in a supersaturated CaP solution. In this study, pseudo-biomineralization was induced in the presence of fluoride ions using the LAB process in order to fabricate an antibacterial fluoride-incorporated apatite (FAp) layer on the dentin surface. After processing for 30 min, a micron-thick FAp layer was formed heterogeneously at the laser-irradiated solid−liquid interface via pseudo-biomineralization. A time-course study revealed that the LAB process first eliminated the pre-existing organic layer, while allowing fluoride incorporation into the dentin surface within 1 min. Within 5 min, FAp nanocrystals precipitated on the dentin surface. Within 30 min, these nanocrystals acquired a pillar-like structure that was weakly oriented in the direction normal to the substrate surface to form a dense micron-thick layer. This layer was integrated seamlessly with the underlying dentin without any apparent gaps. The FAp layer exhibited antibacterial activity against a major oral bacterium, Streptococcus mutans. The proposed LAB process is expected to be a useful new tool for tooth surface functionalization via facile and area-specific pseudo-biomineralization.

Amorphous calcium phosphate (ACP) plays an important role in biomineralization within the three-dimensional (3D) collagen network in human hard tissues, and exhibits osteoconductivity. Porous collagen sponges coated with ACP nanoparticles could be considered as potential scaffolds for use in bone tissue engineering. In this study, such composite materials were fabricated via homogeneous ACP precipitation using a supersaturated calcium phosphate (CaP) solution. Homogeneous ACP precipitation was induced in situ within the sponges by a temperature-controlled coating process composed of two steps. In the first step, the CaP solution was cooled to 4 °C to suppress precipitation until the solution penetrated fully into the sponge's internal pores. In the second step, the CaP solution was warmed up to 25 °C with continuous shaking to induce ACP precipitation within the sponges. The resulting sponges were therefore coated with ACP nanoparticles on their inner and outer surfaces. A simulated body fluid (SBF) test indicated osteoconductivity of the collagen sponges coated with ACP nanoparticles. Further, ACP-coated collagen sponges immobilizing basic fibroblast growth factor (bFGF) were fabricated using the CaP solution supplemented with bFGF. The fabricated sponges allowed the sustained release of bFGF in a culture medium and enhanced proliferation of osteoblastic MC3T3-E1 cells. Such ACP-coated collagen sponges have the potential to be used as scaffolds in bone tissue engineering if pursued for further in vitro and in vivo studies.

Surface functionalization of teeth with fluoride-incorporated apatite layers displays great potential in treatments and prevention of dental disorders. In this study, we used a sintered hydroxyapatite (sHA) substrate as a model material of teeth, and established a rapid and area-specific coating technique of fluoride-incorporated apatite layers by using a laser-assisted biomimetic (LAB) process. In this technique, a sHA substrate was irradiated on the surface with a Nd:YAG pulsed UV laser for 30 min in supersaturated calcium phosphate (CaP) solutions with various fluoride concentrations. The fluoride concentration in the CaP solution was varied to control morphology, crystalline structure, and fluoride content of the resulting layers. Without fluoride in the CaP solution, an octacalcium phosphate (OCP) layer with a flake-like structure was formed on the laser-irradiated surface of the substrate. The addition of fluoride (1000 µM and 3000 µM) to the CaP solution led to the formation of fluoride-incorporated apatite layers with an enamel-like needle-like nanostructure. The fluoride-incorporated apatite layers adhered firmly to the sHA surface and reduced acid dissolution of the sHA substrate by acting as a protective covering. Additionally, the layers released fluoride ions for more than 24 h, and exhibited antibacterial activity relative to a caries-causing bacterium, namely Streptococcus mutans. Thus, our LAB process can potentially act as a new tool for functionalization of tooth surfaces. Statement of Significance We used a sintered hydroxyapatite (sHA) substrate as a model material of teeth, and established a rapid and area-specific coating technique of fluoride-incorporated apatite layers on the sHA surface by using our laser-assisted biomimetic (LAB) process. In this process, pulsed laser was utilized to accelerate seeded crystal growth in supersaturated calcium phosphate solutions supplemented with NaF. The thus-fabricated fluoride-incorporated apatite layers consisted of enamel-like needle-like nanocrystals with c-axis orientation. These fluoride-incorporated apatite layers adhered firmly to the sHA surface, reduced acid dissolution of the sHA substrate by acting as a protective covering, and exhibited antibacterial activity against Streptococcus mutans through the fluoride release. Thus, our LAB process can potentially act as a new tool for functionalization of tooth surfaces.

The structures and morphologies of Al-rich Al–Au alloy nanoparticles thermally oxidized under gaseous oxygen mixtures were investigated by transmission electron microscopy while varying the temperature and oxygen exposure conditions. The exposure of alloy nanoparticles to oxygen at room temperature formed amorphous alumina coatings that protected unoxidized core metals against further oxidation up to approximately 1000 °C. Above this temperature, Au–γ-Al2O3 Janus nanoparticles were generated as a result of complete oxidation. In contrast, the direct oxidation of preheated alloy nanoparticles without oxide coatings enabled complete oxidation to proceed at temperatures as low as 575 °C. Under lower oxygen pressures, direct oxidation resulted in the formation of Au–γ-Al2O3 Janus NPs with worm-like morphologies, suggesting anisotropic oxide growth via interfacial oxidation. In a similar manner, Pt–γ-Al2O3 Janus NPs were generated by the direct oxidation of Al–Pt alloy NPs.

Gold nanoparticles were deposited on two kinds of solid acids, i.e., amorphous SiO 2 –Al 2 O 3 and cation-exchange resin Amberlyst-15; the resultant materials exhibited high activity as metal–acid bifunctional catalysts. SiO 2 –Al 2 O 3 was impregnated with a chloride-free alkaline Au(III) solution containing Na + and then dried. After calcination at 623 K, gold nanoparticles with diameters of 4.2 nm (measured by X-ray diffraction) were deposited at a Au loading of 1.0 wt%. By replacing the Na + ions with H + ions through ammonium ion-exchange and heating, an acidic Au/SiO 2 –Al 2 O 3 catalyst was obtained. In Amberlyst-15, gold nanoparticles with diameters of 7.3 nm were deposited after impregnation and drying. Subsequent ion-exchange with dilute sulfuric acid generated the acidic form of the Au/Amberlyst-15 catalyst, which showed an esterification activity equivalent to that of the original Amberlyst-15. The catalyst exhibited high activity for the direct conversion of cellobiose to gluconic acid, which requires both acid hydrolysis and oxidation. A 45% yield of gluconic acid was obtained after 24 h of reaction under ambient air at 373 K, with an apparent synergistic effect between the gold nanoparticles and acidic resin surface.

We developed a laser fabrication process of submicrometer hollow fluorescent spheres of Tb3+-incorporated calcium phosphate. Pulsed laser irradiation was applied to a dispersion of carbon-integrated hydroxyapatite nanopowders in the presence of Tb3+. Thus, Tb3+ incorporation during calcium phosphate sphere formation through laser processing was achieved.

An easy and versatile method for the preparation of gold nanoparticles catalyst from aqueous alkaline solution of chloride-free gold acetate has been developed. Au nanoparticles can be deposited on various supports only by impregnating them with the stocked solution of it and by the following calcination. Although the solubility of gold acetate is considerably low in water, we have successfully dissolved it completely by refluxing the brown colloidal dispersion of gold acetate with a pH adjusted to 10–11 at the boiling temperature. The resultant solution was transparent without any color, which should contain anionic Au(III) species like Au(OH) 4 − . Metal oxide powder such as Al 2 O 3 , CeO 2 , TiO 2 , SiO 2 as well as silicates such as saponite clay, and Y-type zeolites was impregnated with the solution and then calcined at 623 K. After washing and drying, the deposition of Au nanoparticles ( 2 prepared by this method was more active than those prepared according to conventional deposition–precipitation or impregnation methods by using HAuCl 4 as a source of gold. The smallest mean particle size of Au (2.3 ± 0.8 nm) was obtained on saponite clay, which was highly active for glucose oxidation performed in aqueous phase at 333 K.

Micrometer and submicrometer crystalline silicon spheres were fabricated by selective laser heating of irregular silicon particles in liquid medium. TEM, SEM, XRD, and XPS characterized the structure and morphology of the prepared silicon spheres. The results suggested that they were spherical with a single crystalline structure. In this study, the formation mechanism of the spheres is analyzed, and the process parameters are optimized to obtain high-quality silicon spheres. A theoretical deduction regarding the relationship between critical laser energy density and particle size is also discussed, by which we can predict that larger spheres can be obtained at higher laser energy densities.

Core-shell nanoparticles composed of ferromagnetic cobalt platinum cores covered by non-magnetic silica shells were synthesized by laser ablating a composite target in a helium background gas. The average diameter of the CoPt core was controlled by adjusting the CoPt/SiO2 ratio of the ablation target. The particles were also classified in the gas phase using an electrical mobility classifier. The present method successfully synthesized nearly monodispersed nanoparticles with an average core diameter of 2.5nm. This article describes the synthesis of the core-shell nanoparticles and investigates their magnetic properties.

The dielectric constant is a key parameter that determines both optical and electronic properties of materials. It is desirable to tune electronic properties though dielectric engineering approach. Here, we present a systematic approach to tune carrier mobilities of hybrid inorganic/organic materials where layered two-dimensional transition-metal dichalcogenide TiS2 is electrochemically intercalated with polar organic molecules. By manipulating the dielectric mismatch using polar organic molecules with different dielectric constants, ranging from 10 to 41, the electron mobility of the TiS2 layers was changed three times due to the dielectric screening of the Coulomb-impurity scattering processes. Both the overall thermal conductivity and the lattice thermal conductivity were also found to decrease with an increasing dielectric mismatch. The enhanced electrical mobility along with the decreased thermal conductivity together gave rise to a significantly improved thermoelectric figure of merit of the hybrid inorganic/organic materials at room temperature, which might find applications in wearable electronics.

Transmission electron microscopy was employed to elucidate the morphologies and structures of thermally oxidized gas-phase Al nanoparticles (mean diameter of 10 ± 3 nm) obtained at various temperatures and oxygen pressures. Exposure of the nanoparticles to oxygen at room temperature followed by heating to high temperatures initially generated an amorphous Al2O3 film on the particles that protected the core from further oxidation up to ~1000 °C. However, these particles were completely oxidized to γ-Al2O3 above ~1000 °C. In contrast, exposing bare, preheated Al nanoparticles to oxygen led to direct oxidation to γ-Al2O3 at temperatures as low as ~575 °C. The direct oxidation of Al nanoparticles at 900 °C under low oxygen pressures resulted in the growth of worm-shaped γ-Al2O3 nanoparticles, suggesting anisotropic oxide growth via interfacial oxidation.

Core–shell nanoparticles composed of ferromagnetic cobalt platinum cores covered by non-magnetic silica shells were synthesized by laser ablation of a composite target in a helium background gas. The average diameter of the CoPt core was controlled by adjusting the CoPt/SiO 2 ratio of the ablation target and size-classifying the nanoparticles by an electrical mobility classifier. The present method successfully synthesized nearly monodispersed nanoparticles with an average core diameter as small as 2 nm. The size-dependent magnetic properties of nano-composite films generated by the deposition of nanoparticles onto the substrate were investigated by a SQUID magnetometer.

Monodispersed CoPt alloy nanoparticles were synthesized by a pulsed laser ablation (PLA) technique coupled with a low-pressure operating differential mobility analyzer (LP-DMA). The CoPt alloy nanoparticles were generated by laser ablating a solid Co–Pt target. In CoPt alloy nanoparticles synthesized from a target with a Co composition of 75 at%, the nanoparticle surfaces were covered by an oxide layer and exhibited a core-shell structure. In contrast, no shell was observed in particles generated from a target with a Co:Pt ratio of 50:50 at%. According to an EDX analysis, the compositions of the individual nanoparticles were almost the same as that of the target material. Finally, the magnetic hysteresis loops of the CoPt alloy nanoparticles exhibited ferromagnetism.

Efficient synthesis of l -α-phosphatidyl- d - myo -inositol 3,5-bisphosphate was achieved from 1,2,5,6-diisopropylidene- d -glucose by utilizing ring-closing metathesis and catalytic OsO 4 dihydroxylation.

Based on the solution structures of chiral bidentate lithium amides ((R)-3a,b) having a phenyl group on the chiral carbon, chiral bidentate amines ((R)-5a,b-8a,b and (S)-9a,b) having a bulkier group instead of a phenyl group on the chiral carbon were designed and synthesized.

Using chiral bidentate lithium amides having a bulky group instead of a phenyl group on the chiral carbon, enantioselective deprotonation of prochiral 4-substituted cyclohexanones in the presence of excess trimethylsilyl chloride was examined in THF in the absence and in the presence of HMPA. It is shown that enantioselectivity of the reactions decreases as the substituent on the chiral carbon of the chiral lithium amides and the substituent at the 4-position of cyclohexanones become reasonably bulky. An eight-membered cyclic transition state model is proposed for this deprotonation reaction.

The pendant E-ring moiety of the podophyllotoxin aza-analogue 1 that is a potent inhibitor of microtubule assembly was modified in order to acquire inhibitory activity of DNA topoisomerase II. The monophenolic analogue 2 did not exhibit human topoisomerase II inhibition, while the ortho-quinone 3 that was obtained by oxidation of 2 inhibited its catalytic activity (decatenation) in a dose-dependent manner and stimulated double strand DNA breaks in supercoiled circular plasmid DNA, resulting in the production of linear DNA. These results showed that the topoisomerase II inhibition of the ortho-quinone 3 is due to stabilization of the topoisomerase II-DNA covalent binary complex. On the other hand, the ortho-quinone 3 did not inhibit the relaxation process of supercoiled DNA by topoisomerase I at concentrations up to 400 microM, nor was intercalation observed in unwinding measurements of 3. Therefore, the ortho-quinone 3 was shown to be a novel nonintercalative topoisomerase II specific inhibitor that stabilizes the cleavable complex. The present results suggest that the 4'-free hydroxyl group on the E-ring and the sugar moiety on the C-ring are not a prerequisite for topoisomerase II inhibition by podophyllotoxin derivatives.

Enantioselective deprotonation of 4-tert-butylcyclohexanone was examined using 1-phenylethylamine- and 1-(1-naphthyl)ethylamine-derived chiral lithium amides having an alkyl or a fluoroalkyl substituent at the amide nitrogen. The lithium amides having a 2,2,2-trifluoroethyl group on the amide nitrogen are easily accessible in both enantiomeric forms, and were found to induce good enantioselectivity in the present reaction.

Catalytic protonation of achiral lithium enolates (derived from 2-substituted-1-tetralones), mediated by a chiral tetraamine ligand [( R , R )- N , N ′-bis[1-phenyl-2-(1-piperidinyl)ethyl]-1,3-propanediamine (0.10 equiv.)], was achieved with high enantioselectivity (up to 93% ee) by using water (10% aqueous citric acid) as a proton source. A possible mechanism of highly efficient catalytic turnover of the chiral tetraamine ligand is discussed.

Catalytic asymmetric alkylation of achiral lithium enolates of 1-tetralone and cyclohexanone with reactive alkyl halides was realized by using a combination of a chiral tetradentate amine (∼0.05 equiv.) and an achiral bidentate amine (2 equiv.).

The rate of the reaction of the lithium enolate of 1-tetralone with alkyl halides was enhanced greatly in the presence of 3 equivalents of 1,1,4,7,10,10-hexamethyltriethylenetramine. The ratio of the monoalkylated product to the dialkylated product was found to have increased under a shorter reaction time.

The 1,4-addition reaction of organolithium reagents with 2,6-bis( tert -butyl)-4-methoxyphenyl naphthalenecarboxylates gave regioselectively substituted dihydronaphthalenecarboxylates in high yields. Successive treatment of the esters with organolithiums in THF, lithium triethylborohydride, methyl iodide, and finally sodium borohydride in methanol, provided regio- and stereoselectively the corresponding 1,1,2- and 1,2,2-trisubstituted dihydronaphthalenylmethanols in good yields. This one-flask process is constituted from a sequence of five reactions involving a reductive generation of an aldehyde metal enolate from a ketene as the key step.

Enantioselective asymmetric alkylation of achiral lithium enolates mediated by chiral tetradentate amine ligands is achieved to give chiral quaternary carbon centers. Turnover of a chiral tetradentate amine in the presence of an achiral bidentate amine during the reaction is also realized.

A highly efficient process of aerobic oxidative coupling of 2-naphthol derivatives catalyzed by 1 mol % of Cu(OH)Cl·TMEDA has been developed. Enantioselective oxidative coupling of naphthols was achieved by the use of 10 mol % of chiral catalysts prepared from proline-derived diamines and cuprous chloride, affording the corresponding binaphthols in good enantioselectivities of up to 78% ee. The ester moiety at the 3-position of the substrate was found to be essential for the good asymmetric induction observed in the present coupling reaction.

A method of the conversion of 2,6-bis(tert-butyl)-4-methoxyphenyl dihydronaphthalenecarboxylates into substituted naphthalenes and tetrahydronaphthalenes was developed. Aromatization of substituted dihydronaphthalenecarboxylates with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone and subsequent treatment with ceric ammonium nitrate (CAN) gave the corresponding substituted naphthalenecarboxylic acids. Alternatively, hydrogenolysis and subsequent treatment with CAN provided a way to tetrahydronaphthalenemethanols in good yields.

Enantioselective alkylation of lactams and lactones can be realized up to 98% ee by deprotonation with a chiral tetradentate lithium amide (4b) in the presence of lithium bromide, and subsequent alkylation with active alkylating agents in non-chelating solvents.

A C2 symmetric chiral diether ligand, (1R,2R)-1,2-dimethoxy-1,2-diphenylethane, was designed and synthesized on the basis of the concept of an asymmetric oxygen atom. Mediated by the chiral diether, high enantioselectivities were achieved in conjugate addition of organolithiums to naphthaldehyde imine and cyclic and acyclic α,β-unsaturated aldimines. The absolute configuration of the product is predictable by the model.

The formation of 10 nm scale Si pillars using deposited metal clusters of various kinds (Au, Ag etc) as nuclei for the creation of etch masks has been investigated via microwave plasma etching at about . Experiments using size-selected Ag clusters indicate that the cluster size affects the efficiency of pillar formation but has little effect on the diameter of the fabricated pillars. The average diameter of pillars fabricated with Au clusters is 9 nm, while that with Ag clusters is 19 nm. This is attributed to the difference in chemical reactivity of the clusters with S or F, the components of the etching gas, which results in a different ability to form etch masks by condensation of species.

An efficient enantioselective alkylation of the lithium enolates of cyclohexanone and I-tetralone with reactive alkyl halides was realized using a stoichiometric amount of a tetradentate chiral amine as a ligand for the lithium in the presence of lithium bromide in toluene.

A systematic method for 13C labeling of the glycan of immunoglobulin G for NMR study has been developed. A mouse immunoglobulin of subclass IgG2b has been used for the experiment. On the basis of chemical shift and linewidth data, it has been concluded that (1) the mobility of the carbohydrate chain in IgG2b is comparable to that of the backbone polypeptide chain with the exception of the galactose residue at the nonreducing end of the Man alpha 1-3 branch, which is extremely mobile and (2) agalactosylation does not induce any significant change in the mobility. The results obtained indicate that even in the agalactosyl from the glycans are buried in the protein. Biological significance of the NMR results obtained is also briefly discussed.

1H-NMR spectral studies have shown that lithium-hydrogen interchange between a chiral bidentate amine ( (R)- 3b ) and an achiral tridentate lithium amide (5a) occurs rapidly in THF, favoring the exclusive formation of a chiral bidentate lithium amide ( (R)- 2b ) at equilibrium. This finding was applied to catalytic asymmetric deprotonation of prochiral 4-substituted cyclohexanones (1) using 0.3 equivalent of (R)- 3b in the presence of 2.4 equivalents of 5a in THF in the presence of DABCO and HMPA.

Enantioselective deprotonation of 4-substituted cyclohexanones ( 1a∼d ) by chiral bidentate lithium amides ( (R)- 2a∼j ) having an alkyl- or a fluoroalkyl substituent at the amide nitrogen was examined. (R)- 2i having a 2,2,2-trifluoroethyl group at the amide nitrogen was found to be an excellent chiral base for the present deprotonation reaction. Structures of (R)- 2i in solution and solid state are discussed.

The diastereo- and enantioselective Michael reaction of ketone lithium enolates using a chiral amine ligand (1) was examined. Michael adducts (4) were obtained in excellent chemical yields (95∼99%) with high stereoselectivities ( syn- 4 anti- 4 : 16 84 ∼ 1 99 ; ee of anti- 4 : 81∼99 %) by the reaction between alkyl phenyl ketones (2) and Michael acceptors (3) having an alkylidene group.

6 Li- and 15 N-NMR spectroscopic analyses of a labeled chiral bidentate lithium amide ( [ 6 Li , 15 N 2 ]-(R)- 1 ) have shown that it exists as a chelated monomer ( 5 ) in THF and in DME, as a chelated dimer ( 6 ) in toluene and in ether, while as a chelated monomer ( 5 ) in any of these solvents in the presence of 2 equivalents of HMPA. Solvent-dependent enantioselectivities in deprotonation of 4- tert -butylcyclohexanone ( 2 ) by (R)- 1 appear to be correlated to these solution structures.

Enantioselective deprotonation of prochiral 4-substituted cyclohexanones (4a∼d) by chiral chelated lithium amides (8a≈k) in the presence of excess trimethylsilyl chloride was realized to give the corresponding chiral silyl enol ethers (6a∼d) in up to 89% ee. It is shown that enantioselectivity of the reaction is dependent on the solvent used, but becomes almost independent on the solvent in the presence of HMPA. The sense of asymmetric induction can be correlated to the configuration at the chiral carbon bearing amide nitrogen of the lithium amide. © 1997 Elsevier Science Ltd.

Chiral C 2 -symmetric DMEU derivatives were designed and synthesized as chiral ligands for lithium. The reaction of the lithium enolate ( 2 ) of 1-tetralone ( 1 ) with methyl iodide in toluene in the presence of a DMEU derivative ( 11 ) and hexamethyl-disilazane gave ( S )-2-methyl-1-tetralone ((S)- 3 ) in up to 92% ee.

Enantioselective deprotonation of 4-substituted cyclohexanones (1) in the presence of excess trimethylsilyl chloride was examined using chiral bidentate lithium amides ((R)-3∼(R)-7) in THF. The solution structures of (R)-3a in THF in the presence and in the absence of lithium chloride were studied by NMR. It is concluded that the eight-membered cyclic transition state (10) offers reasonable explanation of the stereochemical course of the present reaction using (R)-3a.

Studies have been made to design chiral bidentate lithium amides and chiral tetradentate amines, and to explore the use of these chiral bases for enantioselective formation and reactions of lithium enolates. Chiral bidentate lithium amides having a chiral amide nitrogen made by virtue of chelation were successfully applied to the enantioselective deprotonation reaction of prochiral cyclic ketones, the kinetic resolution of racemic cyclohexanone derivatives by deprotonation, and the regioselective deprotonation of optically active 3-keto steroids. Structures of some of these chiral bidentate lithium amides in the solid state and in solution were elucidated by X-ray and NMR spectroscopic analyses. By the use of chiral tetradentate amines, enantioselective reactions of lithium enolates with electrophiles, such as alkylation, protonation, and Michael addition, proceeded successfully. Examples of catalytic enantioselective deprotonation, alkylation, and protonation by the present strategy are also presented and discussed.

Clusters, ensemble of atoms and/or molecules with less number enough to form stable bulk, are thought to play important roles in various phenomena such as, crystallization, phase separation, chemical reactions, etc. Several techniques to produce clusters have been developed and studies in this field are becoming active. Two new methods to produce clusters and the investigations on their characteristics are described in this paper. One is the characteristics of clusters formed from liquid (solution), and the other is the formation and the stabilization of clusters on the surface and their structural investigation.

^6Li- and 15N-NMR spectroscopic studies on the solution structures of a chiral tridentate lithium amide have revealed that it exists as a chelated monomer in which the lithium is tri-coordinated, as a chelated dimer in which the lithium is tetra-coordinated, or as a mixture of these two species depending upon the solvent used. It is concluded that lower Lewis acidity of the tri- and tetra-coordinated lithium compared to the di-coordinated lithium makes tridentate lithium amides inferior to dibentate lithium amides as bases in enantioselective deprotonation reaction.

NiO nanorods with extremely high crystallinity were grown by rapid thermal oxidation through exposure of Ni nanoparticles (NPs) heated above 400 ° C to oxygen. Oxidation proceeds by nucleation of a NiO island on a Ni NP that grows anisotropically to produce a NiO nanorod. This process differs completely from that under mild oxidation conditions, where the surface of the NPs is completely covered with an oxide film during the early stage of oxidation. The observed novel behaviour strongly suggests an interfacial oxidation mechanism driven by the dissolution of adsorbed oxygen into the Ni NP sub-surface region, subsequent diffusion and reaction at the NiO/Ni interface. The early oxidation conditions of metal NPs impose a significant influence on the entire oxidation process at the nanoscale and are therefore inherently important for the precise morphological control of oxidized NPs to design functional nanomaterials.

A grazing‐incidence x‐ray diffraction (GIXRD) system combined with cluster formation and deposition chambers was constructed in order to study structures of clusters deposited on a low‐temperature substrate. Clusters are formed by the vapor condensation method with helium gas in the formation chamber. They are injected into the deposition chamber through a nozzle and deposited on a silicon wafer cooled down to the liquid nitrogen temperature. After deposition, GIXRD measurement is carried out without changing vacuum and temperature conditions (in situ). Using the new apparatus, GIXRD measurements were performed on two different kinds of gold cluster deposits prepared on room‐temperature and low‐temperature substrates. The size distribution of gold clusters used for both preparation conditions was measured to be 15±7.5 A by the transmission electron microscope observation of gold clusters sparsely deposited on amorphous carbon film. Diffraction pattern from the room‐temperature deposit of gold clusters sho...

Lithium-hydrogen interchange between a chiral bidentate amine ((R)-4b) and an achiral tridentate lithium amide (8) occurs rapidly in situ, favoring the exclusive formation of a chiral bidentate lithium amide ((R)-5b). Based on this finding, catalytic asymmetric deprotonation of 4-substituted cyclohexanones (1a∼d) was realized by using less than a stoichiometric amount of (R)-4b as a chiral auxiliary.

Enantioselectivity of deprotonation reaction of 4-tert-butylcyclohexanone (2) by a monodentate chiral lithium amide ( (R,R)- 1 ) in THF is strongly influenced by the presence of lithium halides. Aggregation states of this chiral lithium amide in THF-d8 in the absence and in the presence of lithium halides were studied by 6Li and 15N NMR. It is concluded that the mixed dimer (D) is the species to give the high enantioselectivity of the reaction.

The enantioselective Michael reaction of ketone lithium enolates using a chiral amine ligand ( 1 ) was studied. Michael adducts ( 4 ) of up to 94% ee were obtained by the reaction between methyl ketones ( 2 ) and Michael acceptors ( 3 ) having a benzylidene group.