New reactions using old functionality, isocyanides, are described. By using isocyanides in place of carbon monoxide, transformations otherwise difficult to achieve, such as GaCl3-catalyzed [4 + 1] cycloaddition and TfOH-catalyzed insertion into a C–O bond of acetals, are realized. In addition, isocyanides are exploited as a key component in transition-metal-catalyzed C–H bond activation and borylation reactions.
Past and recent advances in the metal-catalyzed asymmetric isomerization of allylic alcohols into carbonyl compounds are discussed in the present Highlight. Emphasis is placed on rhodium, ruthenium, and iridium; the only three metals that have proven successful to date for this most challenging transformation.
We constructed a novel H2 generation system mimicking natural photosynthesis, in which an electron is transported photochemically from ascorbate entrapped in the inner waterpool of vesicles to MV2+ dissolved in the outer aqueous solution and relayed to a Pt(II) complex embedded in the vesicle membrane that acts as a molecular catalyst.
Crown-ether-modified silica nanoparticles (Crown–SNPs) were successfully prepared by simple chemical modifications of silica nanoparticles. The organic moiety introduced into silica nanoparticles was characterized by solid-state 13C NMR and elemental analysis. No morphological damage of silica nanoparticles was recognized according to SEM observation. When an alkali metal salt was added to a solution containing Crown–SNPs, the absorbance changes, whose extent was dependent on the kind and the concentration of a metal ion, were observed.
Iminium salts generated by the oxidation of amino ketene silyl acetals underwent a facile Mannich reaction with another ketene silyl acetal to give aspartic acid derivatives in good yields. The diastereoselectivities were controlled to some extent by using an appropriate isomer of ketene silyl (thio)acetals.
Photocatalytic activity of cerium(IV) oxide (CeO2) particles in decomposition of acetic acid in aqueous suspension was examined under irradiation of visible light. Acetic acid was decomposed to carbon dioxide (CO2) and the rate of CO2 formation was increased by loading of 0.1 wt % cocatalysts (Pt, Au, Rh, Ru, Pd, Ag, Cu, and Ir) on CeO2 by photodeposition. Cocatalysts showed almost the same levels of enhancement of CO2 evolution, i.e., Ag/CeO2 and Cu/CeO2 exhibited rates similar to that of Pt/CeO2. The action spectrum revealed that decomposition of acetic acid was induced by photoabsorption of CeO2.
An efficient and general method has been described for the synthesis of 3-allyl-3-hydroxyoxindole by the reaction of isatins with allyltrimethylsilane in the presence of Bi(OTf)3·4H2O. The method is catalytic and suitable for the preparation of functionalized 3-allyl-3-hydroxyoxindoles.
Pure lithium hexafluorophosphate (LiPF6) was successfully prepared at room temperature (23 °C) by introducing fluorine gas into a reactor containing LiF and P at −196 °C. The mass fractions of LiPF6 and LiF in products prepared at 23 °C were 1.00 and 0.00, respectively, by means of XRD-Rietveld analysis. Namely, the prepared LiPF6 was pure enough to be used as an electrolyte salt in lithium ion batteries.
Heme acquisition system A (HasA), secreted by various gram-negative pathogens, uses a unique histidine–iron–tyrosine (His–Fe–Tyr) coordination to scavenge heme (i.e., protoporphyrin IX–Fe complex) as an iron source. In order to study heme uptake by HasA, we utilized axial ligand mutants and protoporphyrin IX. Our results suggest that the binding of heme in apoprotein is initiated by interactions between heme and hydrophobic residues in the heme pocket. Subsequently, the sequential coordination of Tyr-75 and His-32 with the iron appears to complete holoprotein formation.
Methylenation of aldehydes with bis(iodozincio)methane was performed using a microflow system. Treatment of a dialdehyde with bis(iodozincio)methane in the system can divide two methylenation reactions and realize selective transformation.
Surface segregation of well-defined N-substituted hyperbranched polyamides (HBPA) with various side chain lengths in linear polystyrene matrix was studied. To what extent HBPA was segregated at the surface was dependent on the side chain length, which regulated intermolecular interactions among HBPA molecules via steric hindrance.
Mg-promoted reduction of ethyl cinnamate (1a) in the presence of carbon dioxide gave a mixture of β-carboxylated compound 2a and α,β-dicarboxylated compound 3a. Similar reductive carboxylation of 1a followed by acidic decarboxylation of one of the two geminal carboxyl groups of the generated 3a and esterification afforded selective formation of diethyl phenylsuccinate (2a) in good yield.
Treatment of nylon-6 with supercritical toluene in the presence of small amounts of water resulted in an effective conversion of polyamide to give ε-caprolactam in quantitative yield. The presence of a small amount of water is critical for the progress of the reaction; completely anhydrous conditions failed to achieve depolymerization. ε-Caprolactam was readily isolated after the removal of toluene under reduced pressure. The present method can serve as a useful treatment for the effective chemical recycling of waste plastics. The combined use of hydrocarbon and water is a new technique to control the reactivity of high-temperature water.
We observed the charge reversal of microbubble–polyelectrolyte complexes using microscopic electrophoresis. The measured mobility of microbubbles with the addition of cationic poly(allylamine hydrochloride) exhibited unusual behaviors. The critical concentration of polyelectrolytes added for the charge reversal was not only weakly dependent on chain length but was also much larger than that of colloidal silica–polyelectrolyte complexes. We attribute the nonstoichiometric overcharging to the adsorption–desorption kinetics of hydroxy ions on the surface of genuine microbubbles.
A nickel-catalyzed cycloaddition has been developed where readily available benzoxazinones react with alkynes to afford substituted quinolines or quinolones. The specific cycloaddition can be achieved by tuning a substituent on C2 of benzoxazinone in favor of the formation of quinolines or quinolones selectively.
The Suzuki–Miyaura cross-coupling was found to be effective for the modification of aromatic heterocyclic rings in solvatochromic fluorophores, thereby providing quantitative evaluation of the ring effects on photophysical properties. The effect of heteroatom, a β-substituent, and the number of rings in the aromatic moiety were investigated systematically.
A fed-batch process was used to produce cis,cis-muconic acid from catechol by recombinant Escherichia coli cells expressing the catA gene, which encodes the Pseudomonas putida mt-2 catechol 1,2-dioxygenase responsible for catalyzing ortho-cleavage of catechol, as biocatalysts. We succeeded in producing 415 mM (59.0 g L−1) cis,cis-muconic acid in aqueous solution without generation of by-products in 12 h under the optimal conditions with successive addition of 10 mM catechol. The molar conversion yield based on the amount of consumed catechol was the theoretical value of 100% (mol mol−1).
We synthesized two kinds of poly(1,3-phenyleneethynylenes), one has (+)-menthoxycarbonyl groups at all repeating units and the other has (+)-menthoxycarbonyl groups and n-dodecyloxy groups alternately. Self-supporting membranes could be obtained easily by solvent casting. Enantioselective permeations of the polymers were investigated by pervaporation of 2-butanol. Enantioselective permeabilities of the membrane consisting of one-handed helical foldamer and unfoldamer were clarified.
We synthesized hydroxyapatite (HAp) nanoparticles using a lamellar phase, which was formed using a phosphorous surfactant, sodium dodecylphosphate (SDP). The HAp nanoparticles synthesized using SDP, after calcination, adsorbed more egg white lysozyme compared to that synthesized without SDP.
Pure and Co-doped ZnO nanoparticles were synthesized by a sol–gel method. The structure, morphology, and properties of as-prepared samples have been studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), and ultraviolet–visible absorption spectroscopy (UV–vis) as well as by photoluminescence (PL) spectrometry. The results showed that the diameter of the well-dispersed Co-doped ZnO nanoparticles is about 5 nm and that dopant Co2+ ions substitute Zn2+ ions sites in ZnO nanocrystals without forming any secondary phase. The optical measurements show that the Co doping can effectively tune energy band structure and enrich surface states in both UV and VL regions, which lead to novel PL properties of ZnO nanoparticles. Compared to the undoped sample, a new emission caused by transitions between localized Co2+ d levels appears at 624 nm.
Reaction-pathway control of benzo[b]thiophen-3-yllithium and benzo[b]furan-3-yllithium was accomplished in flow microreactor systems. We could switch between the reaction with an electrophile before ring-opening and that after ring-opening at will by choosing an appropriate residence-time and temperature.
A Lewis acid ionic liquid, 1-[4-(chlorosulfonyl)butyl]-3-methylimidazolium chlorosulfate ([CBMIm]SO3Cl), with Lewis acid sites in both the anion and cation was synthesized. This was demonstrated to be an efficient catalyst for dehydration of aldoximes to nitriles. An unexpected self-induced phase separation of the reaction mixture was observed when the reaction was carried out in acetonitrile. This could be attributed to the hydrolysis of [CBMIm]SO3Cl to regenerate 1-(4-sulfobutyl)-3-methylimidazolium hydrogensulfate ([SBMIm]HSO4), which was the Brønsted precursor of [CBMIm]SO3Cl.
Poly(3-hexylthiophene) was synthesized by the polycondensation of 2-bromo-3-hexylthiophene with a nickel catalyst and (2,2,6,6-tetramethylpiperidin-1-yl)magnesium. The polymerization proceeded at room temperature in a highly regioregular manner.
We synthesized rod-shaped hydroxyapatite (HAp) nanoparticles using sodium bis(2-ethylhexyl) sulfosuccinate (AOT) as an additive in water without an oil. The length of the particles increases from 40 to 100 nm with increasing the concentration ratio AOT/Ca while maintaining a width of 12 nm. These results indicate that an oil phase is not necessarily needed to form the rod-shaped HAp nanoparticles using AOT.
Platinum (Pt) dissolution during oxidation/reduction cycle in various potential cycle ranges and in various pHs of the oxygen-saturated and deaerated H2SO4 and HClO4 electrolyte solutions was monitored by the highly sensitive electrochemical quartz crystal microbalance (EQCM) system. It was found that the Pt mass reduction depended on the potential cycle range and pH of the electrolyte solution with dissolved oxygen. Based on these results, it can be suggested that the dissolution of Pt requires one proton per one Pt and that it also requires dissolved oxygen, and then we can conclude that the dissolution reaction of Pt is as followings; PtO + H+ + 1/2O2 + H2O → Pt(OH)3+ and/or PtOH + H+ + 3/4O2 + 1/2H2O → Pt(OH)3+.
Silica-supported Pd nanoparticles (Pd/SiO2) with dimethyl sulfoxide (DMSO) show excellent catalytic activity and selectivity for the semihydrogenation of alkynes. Small amounts of DMSO drastically suppress the overhydrogenation and isomerization of alkenes. This catalyst system is also applicable to both internal and terminal alkynes. Furthermore, the Pd/SiO2 catalyst was separable from the reaction mixture after the hydrogenation and reusable without loss of its high catalytic activity or selectivity.
We demonstrated the excellent biocompatibility of dendritic platinum nanoparticles (DPNs) in vitro using a cancer cell line (BT-20) and MTT assay. In addition, a successful observation of DPNs within live cells using differential interference contrast (DIC) microscopy without labelling fluorescent dyes has been achieved.
Boron-doped amorphous carbon was synthesized by polymerizing naphthalene and triphenylborane with subsequent heat treatment by spark plasma sintering. The boron-doped carbon material has negative Seebeck coefficient (−0.22 mV K−1), which indicates the carbon material functions as an n-type semiconductor.
A liquid-crystalline phenylterthiophene derivative which exhibits a nematic phase at room temperature has been prepared. The hole mobility in the nematic phase at room temperature reaches 4 × 10−4 cm2 V−1 s−1. This value is two orders of magnitude larger than those of amorphous organic semiconductors and comparable to those in the smectic A or C phases of liquid-crystalline semiconductors.
Ultrafine SnO2 nanoparticles were successfully synthesized by microwave heating. Transmission electron microscopy images revealed that the size of primary particles of the synthesized SnO2 was around 5 nm. The SnO2 nanoparticles worked as a rechargeable electrode material, and the initial lithium insertion capacity of the SnO2 nanoparticles was 1670 mA h g−1 which is significantly larger than that of a specimen synthesized by conventional method.
Two novel thieno[3,4-b]pyrazine-cored molecules, P-DTP and TP-DTP, are synthesized and are characterized by extra large Stokes shifts of over 300 nm. The bulky polyaromatic arms enable these molecules to be solution processible and provide site-isolation on the planar emissive core. They exhibit saturated red electroluminescence in nondoped organic light-emitting diodes fabricated by spin coating.
Nickel-mediated synthesis of cycloparaphenylene (CPP) is described. L-shaped diphenylcyclohexane monomers underwent cyclotrimerization under the influence of [Ni(cod)2]/bipy. X-ray crystal-structure analysis and VT NMR analysis of the thus-formed cyclic trimer confirmed its triangle structure and interesting cyclohexane-flipping behavior in solution. Cyclic trimer was converted to CPP by acid-mediated aromatization. The first X-ray crystal structure of CPP is also described.