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Three-dimensional (3D) representation of a tumor with respect to its size, shape, location, and boundaries is still a challenge in photoacoustic (PA) imaging using artificial contrast agents as probes. We carried out PA imaging of tumors in mice using 800RS-PMPC, which was obtained by coupling of 800RS, a near-infrared cyanine dye, with PMPC, a highly selective tumor-targeting methacrylate polymer having phosphorylcholine side chains, as a probe. The conjugate 800RS-PMPC forms compact nanoparticles (dDLS = 14.3 nm), retains the biocompatibility of the parent polymer (PMPC) and exhibits unprecedented PA performance. When applied to mice bearing a 6 × 3 × 3 mm3 tumor buried 6 mm beneath the skin, the probe 800RS-PMPC selectively accumulates in the tumor and emits PA signals that are strong enough to be unambiguously distinguished from noise signals of endogenous blood/hemoglobin. The PA image thus obtained under high-threshold conditions allows 3D characterization of the tumor in terms of its size, shape, location, and boundaries.

Exogenous nucleic acids showed low efficiency regarding cellular uptake and low stability in biological conditions; therefore, a number of techniques have been developed to improve their basic properties. One of the best solutions is the application of nanosized particles consisting of oligonucleotides that penetrate the cell membrane without any additives and exhibit high stability in cells. In this report, we employed a simple approach to address the basic properties of nanoparticles of oligonucleotides in biological systems. We prepared BODIPY-labeled oligonucleotides that carried an exclusive modification at the strand end. BODIPY shows high hydrophobicity and fluorescent emission; therefore, the oligonucleotides formed nanosized aggregates in aqueous solution and their behaviors in cells or tissues were easily tracked. Detailed experiments revealed that aggregate formation was indispensable for the high cellular uptake of the oligonucleotides via scavenger-receptor-mediated endocytosis. In addition, the aggregates provided an efficient gene regulation in living cells and tumor tissues transplanted into mice.

Molecular oxygen plays an important role in living organisms. Its concentration and fluctuation in cells or tissues are related to many diseases. Therefore, there is a need for molecular systems that can be used to detect and quantify oxygen levels in vitro and in vivo. In this study, we synthesized phosphonated mesoporous silica nanoparticles bearing ruthenium complexes in their pores (pM-Rus) and evaluated their photophysical and biological properties. The pM-Rus were highly soluble in water and showed robust phosphorescence under hypoxic conditions, while the addition of oxygen suppressed this emission. Cellular experiments revealed that pM-Rus with a size of 100 nm showed efficient cellular uptake to emit phosphorescence in hypoxic cells. In addition, pM-Rus have negligible toxicity to cells due to the blockage of direct contact between ruthenium complexes and intracellular biomolecules and the deactivation of singlet oxygen (1O2) generated by photoexcitation of ruthenium complexes before leaking out of the pores. Animal experiments confirmed that pM-Rus showed robust emission at hypoxic regions in mice. Thus, pM-Rus are promising oxygen probes for living systems.

Tumor-selective accumulation of gold nanorods (GNR) has been demonstrated for visualization of tumor hypoxia by photoacoustic imaging. We prepared GNRs with hypoxia-targeting nitroimidazole units (G-NI) on their surface. Biological experiments revealed that G-NI produced a strong photoacoustic signal in hypoxic tumor cells and tissues.

We synthesized mesoporous silica nanoparticles bearing ruthenium complexes in their pores (MSN-Ru) and characterized their photochemical properties. The ruthenium complexes that were immobilized in the pores showed oxygen-dependent phosphorescence, similar to the complexes that were not tethered to nanoparticles. Cellular imaging and in vivo experiments revealed that hypoxic cells and tissues could be visualized by monitoring the phosphorescence of MSN-Ru. Our most important finding was that the toxic effect of singlet oxygen (1O2), which was generated by excitation of the complexes, was effectively suppressed by the deactivation before leaking out from the pores. In addition, we observed a negligible toxic effect of the ruthenium complexes themselves due to the blockage of their direct interaction with intracellular biomolecules. Thus, MSN-Ru is a promising molecular probe of oxygen levels in living cells and tissues.

Homogeneous Sc(OTf)3 used in nitromethane showed excellent catalytic activity for the direct allylation reactions of general alcohols including benzylic, propargylic, allylic, and some aliphatic alcohols with allyltrimethylsilane under mild and neutral reaction conditions. Metal-free β-silyl-substituted carbocations are intermediates generated by the highly oxophilic Sc(OTf)3-assisted rapid removal of a hydroxyl group in alcohols, which is supported by the result that allylation of (R)-1-(naphthalen-2-yl)ethan-1-ol with allytrimethylsilanes using the Sc(OTf)3 catalyst combined with (R)- or (S)-[1,1′-binaphthalene]-2,2′-diol ligands gave only racemic 2-(pent-4-en-2-yl)naphthalene in quantitative yield. The present study resolves the argument about the uncertain catalytic activity of Sc(OTf)3.

Molecular oxygen in living cells is distributed and consumed inhomogeneously, depending on the activity of each organelle. Therefore, tractable methods that can be used to monitor the oxygen status in each organelle are needed to understand cellular function. Here we report the design of a new oxygen-sensing probe for use in the cell nucleus. We prepared "Ru-Hoechsts", each consisting of a phosphorescent ruthenium complex linked to a Hoechst 33258 moiety, and characterized their properties as oxygen sensors. The Hoechst unit shows strong DNA-binding properties in the nucleus, and the ruthenium complex shows oxygen-dependent phosphorescence. Thus, Ru-Hoechsts accumulated in the cell nucleus and showed oxygen-dependent signals that could be monitored. Of the Ru-Hoechsts prepared in this study, Ru-Hoechst b, in which the ruthenium complex and the Hoechst unit were linked through a hexyl chain, showed the most suitable properties for monitoring the oxygen status. Ru-Hoechsts are probes with high potential for visualizing oxygen fluctuations in the nucleus.

Ru3(CO)12-catalyzed divergent ring-opening coupling reactions of a cyclopropenone with methyl acrylate (an electron-deficient alkene) are developed. Under an argon atmosphere, a decarbonylative linear codimer is obtained, while cyclopentenones are obtained under carbon monoxide (20 atm) without decarbonylation. While ruthenium complexes show no catalytic activity for the ring-opening cocyclization of cyclopropenones with ethylene (20 atm) or bicyclo[2.2.1]hept-2-ene (2-norbornene), rhodium complexes, especially [RhCl(η4-1,5-cod)]2, show high catalytic activity for the desired cocyclization reactions to give the corresponding cyclopentenones in high yields and selectivities. In addition, [RhCl(η4-1,5-cod)]2 realizes the catalytic ring-opening co­cyclization of cyclopropenones with internal alkynes to give the corresponding cyclopentadienones. In all these reactions, ruthena- or rhodacyclobutenones are considered to be key intermediates, generated by strain-driven oxidative addition of a cyclopropenone C–C bond to an ­active ruthenium or rhodium species.

Magnetic resonance imaging (MRI) has become a prominent non- or low-invasive imaging technique, providing high-resolution, three-dimensional images as well as physiological information about tissues. Low-molecular-weight Gd-MRI contrast agents (CAs), such as Gd-DTPA (DTPA: diethylenetriaminepentaacetic acid), are commonly used in the clinical diagnosis, while macromolecular Gd-MRI CAs have several advantages over low-molecular-weight Gd-MRI CAs, which help minimize the dose of CAs and the risk of side effects. Accordingly, we developed chiral dendrimer Gd-MRI CAs, which showed high r1 values. The association constant values (Ka ) of S-isomeric dendrimer CAs to bovine serum albumin (BSA) were higher than those of R-isomeric dendrimer CAs. Besides, based on a totally new concept, we developed 13 C/15 N-enriched multiple-resonance NMR/MRI probes, which realized highly selective observation of the probes and analysis of metabolic reactions of interest. This account summarizes our recent study on developing both chiral dendrimer Gd-MRI CAs, and self-traceable 13 C/15 N-enriched phosphorylcholine polymer probes for early detection of tumors.

We designed a chemiluminescent system using nanoparticles. We prepared mesoporous nanoparticles bearing naphthalene endoperoxide as a singlet oxygen generator in the pore and vinyl phenol derivative as an emission unit. The combination of these functional molecules gave highly efficient and bright chemiluminescence through the formation of a 1,2-dioxetane intermediate.

The synthesis of new functional organic molecules that cannot be obtained by a simple combination of conventional synthetic methods is a challenging subject in organic, organometallic, and industrial chemistry as well as in atom-efficient and environmental organic synthesis. Among the various possibilities that have been considered, the catalytic cleavage and reconstruction of the C–C bond has opened the door to a new branch of synthetic organic chemistry. This microreview summarizes progress on the ruthenium- and rhodium-catalyzed strain-driven cleavage of the C–C bond, the methods of which were mostly developed by the author. The direct oxidative addition of 2,5-norbornadienes, cyclopropenones, cyclobutenones, and cyclobutenediones, and to catalytically active metal species followed by the construction of the C–C bond has been used for the preparation of new organic molecules.

In an attempt to monitor μm-level trace constituents, we applied here (1)H-{(13)C-(15)N} triple-resonance nuclear magnetic resonance (NMR) to (13)C/(15)N-enriched l-Dopa as the inevitable precursor of the neurotransmitter dopamine in the brain. The perfect selectivity (to render endogenous components silent) and μm-level sensitivity (700 MHz spectrometer equipped with a cryogenic probe) of triple-resonance allowed the unambiguous and quantitative metabolic and pharmacokinetic analyses of administered l-Dopa/dopamine in the brain and liver of mice. The level of dopamine generated in the brain (within the range 7-76 μm, which covers the typical stimulated level of ∼30 μm) could be clearly monitored ex vivo, but was slightly short of the detection limit of a 7 T MR machine for small animals. This work suggests that μm-level trace constituents are potential targets of ex vivo monitoring as long as they contain N atom(s) and their appropriate (13)C/(15)N-enrichment is synthetically accessible.

Novel chiral dendrimer-triamine-coordinated Gd complexes with polyaminoalcohol end groups were synthesized and shown to have longitudinal relaxivity (r1) values 5 times higher than that of clinically used Gd-DTPA. The affinities of Gd-4a and Gd-4b for bovine serum albumin (BSA), respectively, were estimated by a quartz crystal microbalance (QCM) measurement. The amino groups of the dendrimer were then conjugated with PEG. This conjugation with PEG strongly affected its ability to attenuate signals in T1-weighted MRI.

Polymers are concentration-amplified with respect to the monomeric units. We show here that a phosphorylcholine polymer enriched with (13)C/(15)N at the methyl groups is self-traceable by multiple-resonance (heteronuclear-correlation) NMR in tumor-bearing mice inoculated with the mouse rectal cancer cell line (colon 26). Preliminary measurements indicated that the present polymeric nanoprobe was satisfactorily distinguished from lipids and detectable with far sub-micromolar spectroscopic and far sub-millimolar imaging sensitivities. Detailed ex vivo and in vivo studies for the tumor-bearing mice administered the probe with a mean molecular weight of 63,000 and a mean size of 13 nm, revealed the following: (1) this probe accumulates in the tumor highly selectively (besides renal excretion) and efficiently (up to 30% of the injected dose), (2) the tumor can thus be clearly in vivo imaged, the lowest clearly imageable dose of the probe being 100 mg/kg or 2.0 mg/20-g mouse, and (3) the competition between renal excretion and tumor accumulation is size-controlled; that is, the larger (higher molecular-weight) and smaller (lower molecular-weight) portions of the probe undergo tumor accumulation and renal excretion, respectively. The observed size dependence suggests that the efficient tumor-targeting of the present probe is stimulated primarily by the so-called enhanced permeability and retention (EPR) effect, that is, size-allowed invasion of the probe into the tumor tissue via defective vascular wall. Self-traceable polymers thus open an important area of magnetic resonance imaging (MRI) of tumors and may provide a highly potential tool to visualize various delivery/localization processes using synthetic polymers.

Magnetic resonance imaging (MRI) has become a prominent non- or low-invasive imaging technique, providing high-resolution, three-dimensional images as well as physiological information about tissues. Low-molecular-weight Gd-MRI contrast agents (CAs), such as Gd-DTPA (DTPA: diethylenetriaminepentaacetic acid), are commonly used in the clinical diagnosis, while macromolecular Gd-MRI CAs have several advantages over low-molecular-weight Gd-MRI CAs, which help minimize the dose of CAs and the risk of side effects. Accordingly, we developed chiral dendrimer Gd-MRI CAs, which showed high r

The synthesis of new functional organic molecules that cannot be obtained by a simple combination of conventional synthetic methods is a challenging subject in organic, organometallic, and industrial chemistry as well as in atom-efficient and environmental organic synthesis. Among the various possibilities that have been considered, the catalytic cleavage and reconstruction of the C–C bond has opened the door to a new branch of synthetic organic chemistry. This microreview summarizes progress on the ruthenium- and rhodium-catalyzed strain-driven cleavage of the C–C bond, the methods of which were mostly developed by the author. The direct oxidative addition of 2,5-norbornadienes, cyclopropenones, cyclobutenones, and cyclobutenediones, and to catalytically active metal species followed by the construction of the C–C bond has been used for the preparation of new organic molecules.

Novel chiral dendrimer–triamine-coordinated Gd complexes were synthesized and shown to have longitudinal relaxivity ( r 1) 3 times higher than that of clinically used Gd-DTPA. The pharmacokinetic differences between optical isomers were estimated from the affinity of 2-( R ) and 2-( S ) with bovine serum albumin (BSA), respectively, by a quartz crystal microbalance (QCM) measurement. As a result, the association constant K a of 2-( S ) was about 4 times higher than that of 2-( R ) , which means that 2-( S ) is retained in the vascular retention for a longer time after administration. This result was also supported by T1-weighted MR images of mice before and after the intravenous injection of 2-( R ) and 2-( S ) , as well as the time-course of the signal intensities (SI) at the blood vessels and quantification of Gd 3+ concentration in the blood and urine.

We report the application of one-dimensional triple-resonance NMR to metabolic analysis and thereon-based evaluation of drug activity. Doubly (13)C/(15)N-labeled uracil ([(15)N1,(13)C6]-uracil) was prepared. Its catabolic (degradative) conversion to [(13)C3,(15)N4]-β-alanine and inhibition thereof by gimeracil, a clinical co-drug used with the antitumor agent 5-fluorouracil, in mouse liver lysates were monitored specifically using one-dimensional triple-resonance ((1)H-{(13)C-(15)N}) NMR, but not double-resonance ((1)H-{(13)C}) NMR, in a ratiometric manner. The administration of labeled uracil to a mouse resulted in its non-selective distribution in various organs, with efficient catabolism to labeled β-alanine exclusively in the liver. The co-administration of gimeracil inhibited the catabolic conversion of uracil in the liver. In marked contrast to in vitro results, however, gimeracil had practically no effect on the level of uracil in the liver. The potentiality of triple-resonance NMR in the analysis of in vivo pharmaceutical activity of drugs targeting particular metabolic reactions is discussed.

Low-valent ruthenium complexes often show intriguing and characteristic catalytic activity for novel organic transformations with high atom efficiency. The design and synthesis of novel low-valent ...

The controlled calcination of ruthenium complexes together with an aminosilsesquioxane ligand ( 1 ) at 823 K in air stream for 4 h afforded porous silicas including monodispersed ruthenium oxide nanoparticles with high surface areas and uniformly controlled micropores. Bimodal porous oxides with both meso- and micropores were prepared by the impregnation of Ru complexes and 1 onto titania (JRC-TIO-4) or silica (JRC-SIO-1), followed by the careful calcination at 823 K. These bimodal catalysts showed higher activity towards hydroformylation of 1-octene (C 9 -aldehydes yield up to 31%, linear selectivity up to 95% in CO 20 atm, H 2 25 atm at 403 K for 20 h with 1.5 mol% Ru catalyst) than the catalysts prepared without an aminosilsesquioxane ligand.

Novel Ti-containing silsesquioxane gel catalysts were prepared by the hydrosilylative condensation of Ti-containing silsesquioxanes together with cubic silsesquioxanes and spherosilicates. The porosity of gels was controlled by changing the composition and the mixing order of the starting materials. Both porous and nonporous gels were found to act as excellent heterogeneous catalysts towards the selective epoxidation of cyclooctene by the use of aqueous hydrogen peroxide as an oxidant.

Novel catalytic reactions via ruthena- or rhodacyclic intermediates have been developed by our research group. We initiated our study from (1) ruthenium-catalyzed [2+2] cycloaddition of alkynes with alkenes, followed by developing (2) intramolecular Pauson-Khand-type reaction of 1,6-enynes, (3) hydroquinone synthesis, (4) cyclocotrimerization reactions, and (5) codimerization of styrenes with ethylene. Another approach to construct novel functional monomers, such as cyclopentenones, pyranopyrandiones, and substituted phenols, involves cleavage of carbon-carbon bonds in cyclobutenediones, cyclopropenones, and cyclobutenones. All reactions may proceed with high atom-efficiency via ruthena- or rhodacyclic intermediates, represented by ruthenacyclopentene, (maleoyl)ruthenium, and rhodacyclopentenone intermediates. In addition, rhodium-catalyzed [2+2+2] cocyclization of alkynes with isocyanates as well as novel ruthenium-catalyzed [2+2+1] cocyclization of alkynes, isocyanates, and carbon monoxide have been disclosed. 1 Introduction 2 Ruthenium-Catalyzed Cycloaddition of Alkynes with Alkenes 2.1 [2+2] Cycloaddition of Alkynes with 2-Norbornenes 2.2 Intramolecular Pauson-Khand-Type Reaction of Enynes with Carbon Monoxide 2.3 Cross-Carbonylation of Alkynes with 2-Norbornenes or Electron-Deficient Alkenes to Hydroquinones 2.4 Synthesis of Benzenepolycarboxylates by Cross-Benzannulation of Acetylenedicarboxylates with Allylic Compounds 2.5 [2+2+2] Cocyclization of Three Different Alkynes 2.6 Regio- and Stereoselective Dimerization of Styrenes and Linear Codimerization of Styrenes with Ethylene 3 Ruthenium- and Rhodium-Catalyzed Cleavage of C-C Bonds Leading to Reconstructive Synthesis of Novel Functional Monomers 3.1 Ru-Catalyzed Selective Monodecarbonylative Coupling of Cyclobutenediones with Alkenes to Cyclopentenones 3.2 Ru-Catalyzed Carbonylative Dimerization of Cyclopropenones and Cross-Carbonylation of Cyclopropenones with Alkynes to Pyranopyrandiones 3.3 Ru- and Rh-Catalyzed Ring-Opening Reactions of Cyclobutenones 3.4 Rh-Catalyzed Direct Synthesis of Substituted Phenols from Cyclobutenones and Electron-Deficient Alkenes 4 Ruthenium- and Rhodium-Catalyzed Cocyclization of Alkynes and Isocyanates 4.1 Rh-Catalyzed Cyclocotrimerization of Alkynes and Isocyanates to 2-Pyridones or Pyrimidine-2,4-diones 4.2 Ru-Catalyzed [2+2+1] Cocyclization of Alkynes, Isocyanates, and Carbon Monoxide 5 Summary

Novel catalytic reactions via ruthena- or rhodacyclic intermediates developed by our research group are reviewed. We initiate our study from (1) ruthenium-catalyzed [2 + 2] cycloaddition of alkynes with alkenes, followed by developing (2) intramolecular Pauson-Khand-type reaction of 1, 6-enynes, (3) hydroquinone synthesis, (4) codimerization of styrenes with ethylene . Another approach to construct novel functional monomers, such as cyclopentenones, pyranopyrandiones, and phenols, involves cleavage of carbon-carbon bonds in cyclobutenediones, cyclopropenones, and cyclobutenones. All reactions proceed with high atom-efficiency via ruthena- or rhodacyclicintermediates. In addition, rhodium-catalyzed [2 + 2 + 2] cocyclization of alkynes with isocyanates as well as novel ruthenium-catalyzed [2 + 2 + 1] cocyclization of alkynes, isocyanates, and carbon monoxide have been disclosed.

Silsesquioxanes containing tetrapodal titanium species and alkenylsilyl groups were immobilized onto dimethylsilyl-functionalized silica having mesopores by chemical tethering via hydrosilylative reaction in the presence of a Pt catalyst. The immobilized catalysts showed higher activity than their corresponding homogeneous catalyst towards the epoxidation of cyclooctene by tert-butylhydroperoxide, probably because of the improvement of the micro-environment around the titanium center. The reaction was found to be truly heterogeneous, since no further reaction proceeded after the separation of the catalyst by filtration. These catalysts also showed excellent catalytic activity for the epoxidation using hydrogen peroxide as an oxidant, while the parent homogeneous catalysts did not show any activity at all.

Ruthenium complex-catalyzed reactions often require highly qualified tuning of reaction conditions with substrates to attain high yield and selectivity of the products. In this review, our strategies for achieving characteristic ruthenium complex-catalyzed co-oligomerization of different alkenes are disclosed: 1) The codimerization of 2-norbomenes with acrylic compounds by new ruthenium catalyst systems of RuCl 3 (tpy)/Zn [tpy = 2,2':6',2"-terpyridine] or [RuCl 2 (η 6 -C 6 H 6 )] 2 /Zn in alcohols, 2) A novel synthesis of 2-alkylidenetetrahydrofurans from dihydrofurans and acrylates by zerovalent ruthenium catalysts, such as Ru(η 4 -cod)(η 6 -cot) [cod = 1,5-cyclooctadiene, cot = 1,3,5-cyclooctatriene] and Ru( η 6 -cot)( η 2 -dmfm) 2 [dmfm = dimethyl fumarate], 3) Regio- and stereoselective synthesis of enamides by Ru(η 6 -cot)(η 2 -dmfm) 2 -catalyzed codimerization of N-vinylamides with alkenes, and 4) Unusual head-to-head dimerization of styrenes and linear codimerization of styrenes with ethylene by Ru(η 6 -cot)(η 2 -dmfm) 2 catalyst in the presence of primary alcohols.

A novel (μ 3 -oxo)tetraruthenium cluster ( 2 ) was synthesized in an isolated yield of 73% by the reaction of a zerovalent ruthenium complex, Ru(η 6 -cot)(η 2 -dmfm) 2 ( 1 ) [cot = 1,3,5-cyclooctatriene, dmfm = dimethyl fumarate], with water under reflux in 1,4-dioxane for 6 h. The structure and the X-ray characterization of this novel complex 2 as well as a possible formation mechanism of 2 are disclosed.

A novel zerovalent ruthenium complex with a π-acidic ligand, Ru(η (6)-cyclooctatriene)(η (2)-dimethyl fumarate)2 (1), was prepared from Ru(η (4)-cyclooctadiene)(η (6)-cyclooctatriene) [Ru(cod)(cot)]. Complex 1 or Ru(cod)(cot) catalyzes various new carbon-carbon bond-forming reactions that include the [2 + 2] cycloaddition of alkenes and alkynes via ruthenacycles, the creation of a new hydrocarbon, pentacyclo[6.6.0.0(2,6).0(3,13).0(10,14)]tetradeca-4,11-diene [PCTD], by dimerization of 2,5-norbornadiene via C-C bond cleavage, and the codimerization of alkynes and/or alkenes. Complex 1 was shown to be an excellent mother complex for various zerovalent ruthenium complexes. Complex 1 reacts with amines, phosphines or water to give new zerovalent ruthenium complexes with the ligands. The resulting aqua complexes have a water ligand with an oxygen atom that is a chiral center, i.e., ruthenium complexes with a 'chiral water' ligand were prepared and fully characterized.

A (13)C-enriched phosphorylcholine polymer ((13)C-PMPC) as a self-traceable MR (magnetic resonance) tag was conjugated with a fragment (scFv) of Herceptin, a clinical antibody against antigen Her2. When injected in model mice bearing Her2(+) (gastric) and Her2(-) (pancreatic) tumors, the antibody-tag conjugate (13)C-PMPC-scFv selectively accumulated in the Her2(+) tumor with a rapid build-up/decay (accumulation/clearance) profile and, with the use of the (1)H-(13)C double-resonance (heteronuclear correlation) technique, the Her2(+) gastric tumor was clearly MR imaged.

A neutral rhodium(I) complex, ‘RhCl(PPh 3 ) 2 ’ generated by the combination of [RhCl(C 2 H 4 ) 2 ] 2 with a fourfold amount of PPh 3 , effectively catalyzed the cyclocotrimerization of alkynes ( 1 ) and isocyanates ( 2 ) to give 2-pyridones ( 3 ) and/or pyrimidine-2,4-diones ( 4 ), selectively, by controlling the molar ratio of alkynes ( 1 ) and isocyanates ( 2 ).

The controlled calcination of Pd complexes bearing a silsesquioxane-amine ligand ( c -C 5 H 9 ) 7 Si 7 O 10 {OSi(Me 2 )CH 2 CH 2 CH 2 NH 2 } ( 1 ), at 823 K in air stream for 4 h afforded porous silicas of high surface areas and uniformly controlled micropores of ca. 0.6 nm diameter encapsulating monodispersed palladium oxide nanoparticles. The calcination after the impregnation of palladium complexes bearing 1 onto titanium oxide afforded oxides with both meso- and micropores. These catalysts showed excellent catalytic activities towards the aerobic oxidation of benzyl alcohol, especially even in water (benzaldehyde yield up to 87% in air at 353 K for 24 h with 0.10 mol% Pd).

Reactions of a zerovalent ruthenium complex, Ru(η4-cod)(η6-cot) (3; cod = 1,5-cyclooctadiene, cot = 1,3,5-cyclooctatriene), with maleic anhydride or maleimides under mild reaction conditions afforded a series of novel divalent ruthenacycles 4 with an η5-cyclooctadienyl moiety via oxidative cyclization between the carbon−carbon double bonds of cot and the electron-deficient alkene. The solid-state structure clearly showed a newly constructed ruthenacycle skeleton, which was formed in a trans manner. Complex 4 was further reacted with H2 and HCl to give hydrogenated and protonated succinimides with a C8-ring, respectively. When 4 was heated in toluene, a [6 + 2] cycloadduct of cot and a maleimide was obtained via reductive elimination, which shows that a ruthenium-mediated stepwise [6 + 2] cycloaddition was achieved. The addition of PPh3 to complex 4d promoted the reductive elimination, while bidentate phosphines such as 1,2-bis(diphenylphosphino)ethane did not give the cycloadduct and stable ruthenacycles ...

The reaction of Ru(η6-cot)(dmfm)2 (1; cot = 1,3,5-cyclooctatriene, dmfm = dimethyl fumarate) with water and dppe derivatives (dppe = 1,2-bis(diphenylphosphino)ethane) having two or four methoxy gro...

Palladium acetate together with a newly synthesized silsesquioxane- pyridyl ligand showed excellent catalytic activity towards the aerobic oxidation of benzyl alcohol to benzaldehyde. TEM measurements revealed the in situ formation of Pd nanoclusters during the reaction period.

The chemistry of a novel zerovalent Ru complex, Ru(η6-cot)(η2-dmfm)2 (1) (cot=1,3,5-cyclooctatriene; dmfm=dimethyl fumarate), is reviewed with a focus on its reactivity toward phosphines, amines, and H2O, as well as arenes and p-quinones. A variety of novel zerovalent Ru complexes were synthesized from Ru(η6-cot)(η2-dmfm)2 (1), and it was shown that the complexes preferably bear both electron-donating and -accepting ligands simultaneously to exhibit thermodynamic stability. The first isolable zerovalent Ru aqua complexes were successfully prepared, and in these complexes, the generation of a chiral center on the O atom of the coordinated H2O was disclosed. In addition, the characteristic catalytic activity of 1 in organic synthesis was considered by reviewing recently developed novel reactions: (i) dimerization of 2,5-norbornadiene to pentacyclo[6.6.0.02,6.03,13.010,14]tetradeca-4,11-diene (PCTD), (ii) intramolecular hydroamination of aminoalkynes to cyclic imines, (iii) formal [4+2] cycloaddition of alkynes with dmfm to trans-4-cyclohexene-1,2-dicarboxylates, and (iv) co-dimerization of dihydrofurans with α,β-unsaturated esters to 2-alkylidenetetrahydrofurans. The products obtained here are expected to be used as novel functional organic monomers. © 2006 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 6: 107–116; 2006: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20076