Gold-catalyzed isomerization of unactivated allenes into 1,3-dienes under ambient conditions

We have developed a gold-catalyzed isomerization of unactivated allenes into 1,3-dienes with nitrosobenzene as an additive. This reaction proceeded almost exclusively at room temperature for highly substituted allenes. The utility of this reaction is manifested by the development of one-pot [4+2]-cycloaddition of allenes and reactive alkenes.     

Molybdenum-catalyzed reduction of molecular dinitrogen into ammonia under ambient reaction conditions

Synthesis of transition metal–dinitrogen complexes and stoichiometric transformations of their coordinated dinitrogen into ammonia and hydrazine have so far been well investigated in order to achieve a novel nitrogen fixation under ambient conditions. As an extension of our study, the dimolybdenum–dinitrogen complex bearing PNP pincer ligands has been found to work as an effective catalyst for the formation of ammonia from dinitrogen, where 52 equiv of ammonia are produced based on the catalyst (26 equiv of ammonia are produced based on the molybdenum atom of the catalyst). This is the most effective catalytic reaction system for the formation of ammonia from molecular dinitrogen catalyzed by transition metal–dinitrogen complexes as catalysts under ambient reaction conditions. Herein, we describe recent results concerning the catalytic reaction, including the proposed reaction pathway.     

Site-specific modification of amino acids and peptides by aldehyde-alkyne-amine coupling under ambient aqueous conditions

A highly efficient method for the direct, site-specific functionalization of amino acids and peptides, under ambient conditions, is described. In aqueous, nearly solvent-free conditions, copper(I) chloride catalyzed the aldehyde-alkyne-amine (A(3)) coupling of amino acids to form dipropargylated products in moderate to excellent yields. The propargylamine functionality provides a convenient handle for further structural modifications, demonstrated by a subsequent one-pot deprotection and "click" reaction and a solution-phase peptide coupling.     

Reversible photoregulation of helical structures in short peptides under indoor lighting/dark conditions

[reaction: see text] A photochromic cross-linking agent with a spiropyran skeleton was developed for the reversible photoregulation of helical structures in short peptides. The helical contents of the cross-linked peptides could be regulated by ambient light and dark conditions at room temperature. This switching of the helical contents could be repeated several times without substantial loss of any activity.     

Metallisation of gel surfaces under ambient conditions

A room temperature method to coat a non-conducting gel phase with a metal is described, which uses galvanic displacement. Electrolytes are dissolved in the gel phase to allow metal deposition from an immiscible liquid electrolyte solution. Conformal deposition was achieved by imprinting the gel, followed by galvanic displacement of gold.     

Photopromoted carbonylation of bromobenzene under ambient conditions

The photopromoted carbonylation of bromobenzene with carbon monoxide catalyzed by inexpensive commercially available cobalt salts[Co(OAc)_2,CoCl_2]was carried out under ambient conditions.The results revealed that methyl benzoate was produced in the presence of basic additives(CH_3ONa,NaOAc or(n-C_4H_9)_3N).The catalytic activity of Co(OAc)_2was higher than that of CoCl_2.Furthermore,the activity of the carbonylation was greatly improved by addition of acetophenone,e.g.both the yield and selectivity of t...     

Asymmetric hydrogenation of chiral vinyloxazaborolidines under ambient conditions

Novel homochiral vinyloxazaborolidines have been synthesized and subsequently hydrogenated using palladium on carbon under ambient conditions to produce, after oxidation of the boronate group, enantiomerically enriched secondary alcohols (up to 20% ee). Herein, the first example of asymmetric hydrogenation utilizing oxazaborolidines as chiral auxiliaries is reported.     

Dimer formation of organic fluorophores reports on biomolecular dynamics under denaturing conditions

Stacking interactions between organic fluorophores can cause formation of non-fluorescent H-dimers. Dimer formation and dissociation of two fluorophores site-specifically incorporated in a biomolecule result in fluorescence intermittency that can report on conformational dynamics. We characterize intramolecular dimerization of two oxazine fluorophores MR121 attached to an unstructured polypeptide. Formation of stable non-fluorescent complexes with nano- to microsecond lifetimes is a prerequisite for analysing the intermittent fluorescence emission by fluorescence correlation spectroscopy and extracting relaxation time constants on nano- to millisecond time scales. Destabilization of the generally very stable homodimers by chemical denaturation reduces the lifetime of H-dimers. We demonstrate that H-dimer formation of an oxazine fluorophore reports on end-to-end contact rates in unstructured glycine-serine polypeptides under denaturing conditions.     

Titanium substrate based micro-PEMFC operating under ambient conditions

A novel design and fabrication technique of micro-PEMFC based on titanium substrate is described. The titanium substrate was fabricated with microflow channels using microfabrication techniques, followed by surface treating and coating with a microporous layer (MPL). It served as a combined functional component as gas diffusion layer, current collector and flow plate. A catalyst coated membrane (CCM), fabricated by directly coating catalyst layer onto Nafion 112 membrane, was integrated with the titanium substrates to assemble the micro-PEMFC. The titanium substrate based micro-PEMFC showed some unique characteristics and acceptable performance while operating under ambient conditions.     

P-type nitrogen-doped ZnO nanoparticles stable under ambient conditions

Zinc oxide is considered as a very promising material for optoelectronics. However, to date, the difficulty in producing stable p-type ZnO is a bottleneck, which hinders the advent of ZnO-based devices. In that context, nitrogen-doped zinc oxide receives much attention. However, numerous reviews report the controversial character of p-type conductivity in N-doped ZnO, and recent theoretical contributions explain that N-doping alone cannot lead to p-typeness in Zn-rich ZnO. We report here that the ammonolysis at low temperature of ZnO(2) yields pure wurtzite-type N-doped ZnO nanoparticles with an extraordinarily large amount of Zn vacancies (up to 20%). Electrochemical and transient spectroscopy studies demonstrate that these Zn-poor nanoparticles exhibit a p-type conductivity that is stable over more than 2 years under ambient conditions.     

Ultrasound-promoted synthesis of nitriles from aldoximes under ambient conditions

Copper(II) acetate proves to be an active catalyst for ultrasound-promoted conversion of aldoximes into nitriles. This dehydration reaction was carried out in acetonitrile under ambient conditions to provide nitriles with moderate tolerance toward water, which allows one-pot synthesis of a nitrile from an aldehyde with minimal purification.     

Cyclization under mild conditions of cysteine containing peptides

Cyclization of di- and tripeptides containing cysteine as N-terminal residue is reported. The preferred cyclization patterns and the nature of the products (diketopiperazine, aza-cyclol, peptide thiolactone) are discussed.     

Highly sensitive detection of saccharides under physiological conditions with click synthesized boronic acid-oligomer fluorophores

Two phenylboronic acid based saccharide sensors bearing conjugated oligomer fluorophores with linear and cruciform π-frameworks were synthesized in a modular approach utilizing a Cu-catalyzed alkyne azide cycloaddition (click) reaction. The cruciform fluorophore showed excellent saccharide sensing function under physiological conditions in the mM range, whereas the linear fluorophore gave very limited sensing functions. The different fluorescent sensing behaviours highlight the important role of oligomer fluorophore in the development of effective saccharide sensors.     

Activation of olefins with low-valent gallium compounds under ambient conditions

The reactions of Ar'GaGaAr' (Ar' = C(6)H(3)-2,6-(C(6)H(3)-2,6-(i)Pr(2))(2)) with alkenes revealed the addition of two olefins per Ar'GaGaAr' under ambient conditions for ethylene, propene, 1-hexene and styrene but no reactions with more hindered or cyclic olefins.     

The reactions of tellurium tetrahalides with triphenylphosphine under ambient conditions

The reactions of tellurium tetrahalides and triphenylphosphine in tetrahydrofuran have been carried out under ambient conditions and afford [(Ph(3)PO)(2)H](2)[Te(2)X(10)] [X = Cl (1), Br (2)] and [(Ph(3)PO)(3)(OH(3)])(2)[TeI(6)] (4). The X-ray structures of 1 and 2 show that they are isostructural and contain discrete [Te(2)X(10)](2-) anions exhibiting octahedral coordination around both tellurium atoms with one shared edge and [Ph(3)POH...OPPh(3)](+) cations that show strong hydrogen bonds (the O...O distances are 2.399 and 2.404 A for 1 and 2, respectively). The compound 4 is built up with discrete octahedral hexaiodotellurate anions and [(Ph(3)PO)(3)(OH(3))](+) cations. The reaction of TeBr(4) and PPh(3) also results in the formation of formally zwitterionic Ph(3)PO(CH(2))(4)TeBr(4) (3). This reaction involves an unprecedented THF ring opening in which the oxygen atom becomes bonded to the phosphorus atom of triphenylphosphine and the carbon atom at the other end of the five-atomic chain becomes bonded to the tellurium atom of TeBr(4). The ring opening of the solvent THF is also taking place in the reaction involving tellurium tetraiodide, as indicated by the formation of C(4)H(8)TeI(2) (5). The reaction may initially lead to Ph(3)PI(2) that reacts with THF yielding Ph(3)PO and ICH(2)(CH(2))(2)CH(2)I. The latter species reacts with elemental tellurium producing 5. Depending on the conditions upon crystallization, two polymorphs of C(4)H(8)TeI(2) (5a and 5b) are observed. While the molecular structures of the two forms are virtually identical, their packing and intermolecular contacts are different. Two further minor products (6a and 6b) were isolated in the reaction of TeI(4) and PPh(3): Both are formally 1:1 adducts of 5 and TeI(4), but they differ considerably in their structures. 6a can be formulated as [C(4)H(8)TeI(+)](2)[Te(2)I(10)(2-)] and 6b as [C(4)H(8)TeI(+)](2)(TeI(3)(+))(2)(I(-))(4). The latter compound exhibits framework similar to that of the tetramers in gamma- and delta-TeI(4).     

Photopromoted carbonylation of 1-bromo-6-chlorohexane under ambient conditions

Photopromoted carbonylation of 1-bromo-6-chlorohexane with CO catalyzed by CuBr2 and CdI2 has been carried out under ambient conditions. The results indicate that the carbonylation proceeds with the major product of chloroester ClCH2（CH2）5COOCH3 under catalysis of CuBr2. Furthermore, the activity of the carbonylation can be improved by addition of basic additives （NaOAc, Na3PO4 or （n-C4H9）3N）. Among these additives, （n-C4H9）3N is the most efficient in terms of the yield of ClCH2（CH2）5COOCH3. However, the methoxycarbonyl substituting chlorine product of BrCH2（CH2）5COOCH3 is not obtained in the presence of CdI2. This is quite different from the carbonylation of monochloroalkane.     

Copper-catalyzed direct sulfoximination of azoles and polyfluoroarenes under ambient conditions

The direct dehydrogenative C-N coupling of azoles or polyfluoroarenes with N-H sulfoximines proceeds effectively in the presence of a copper catalyst at room temperature under air to afford the corresponding N-arylsulfoximines in good to high yields.     

A sonochemical route to single-walled carbon nanotubes under ambient conditions

A chemical route to single-walled carbon nanotubes (SWCNTs) under ambient conditions has been developed. Silica powder was immersed in a mixture solution of ferrocene and p-xylene. After sonication at atmospheric pressure and room temperature, we obtained high-purity SWCNTs. Sonochemical effects may lead to producing high-purity SWCNTs. The process could be readily generalized to synthesize other forms of carbon-based materials, such as fullerenes, multiwalled nanotubes, carbon onions, and diamond, in liquid solution under ambient conditions.