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A highly simple, economical, and selective synthesis of five-membered cyclic carbonates was achieved by the reaction of CO2 with 1,2-halohydrins in the presence of K2CO3. This method allows the efficient preparation of cyclic carbonates (72–95% yields for monosubstituted cyclic carbonates and 43% for 1,1- and 1,2-disubstituted cyclic carbonates) under mild reaction conditions, atmospheric pressure of CO2 at 30 °C, and not only in dry DMF, but also in commercial “anhydrous” DMF. The reaction mechanism was elucidated using the SEM and XRD data of the by-products, KHCO3 and KBr.

An efficient, metal- and solvent-free catalytic system was developed for the conversion of CO2 and epoxides to the corresponding cyclic carbonates under mild conditions (T = 25–45 °C, 1 atm CO2) in high-to-excellent yields. The catalyst could be easily recycled, providing a more sustainable process for the chemical fixation of CO2.

Palladium(0)-catalyzed insertion/annulation sequence between aryl silylethynyl ethers and internal alkynes was found to proceed through activation of ortho-C–H bonds assisted by alkynoxy groups and...

The synthesis, crystal structures, and magnetic properties of the pentanary oxides PbM2Ni6Te3O18 (M = Mn and Cd) were investigated. These compounds crystallize in a hexagonal structure with space group P63/m, in which the Ni(2+) ions form a zigzag chain along the c axis. From the magnetic susceptibility and specific heat measurements, we found that the PbCd2Ni6Te3O18 behaves as a low-dimensional magnet due to the intrachain antiferromagnetic interaction between Ni(2+) ions. Both compounds show a long-range antiferromagnetic ordering at 25.7 K (M = Cd) and 86.0 K (Mn). The magnetic structure of PbMn2Ni6Te3O18 determined by neutron diffraction measurements is a collinear antiferromagnetic arrangement of Mn(2+) ions in the Mn2O9 dimeric unit and Ni(2+) ions in the zigzag chain.

o-Alkynylphenols are found to undergo a Pd/Zn-catalyzed dehydrogenative formation of benzocyclobutene derivatives involving the o-alkynyl substituent as internal hydrogen acceptor.

The isolation and structure elucidation of kaempulchraols I (Ia), J (Ib), K (IIa), L (IIb), M (III), N (IVa), and O (IVb) is described.

A novel [4 + 2] cycloaddition to synthesize the title compounds bearing two chiral centers with high enantio- and diastereoselectivity is developed using the coupling reaction of isochromene acetals (I) with alkenyl boronates.

Nucleic acids are the principal materials for the preservation and flow of genetic information. The control of the properties of nucleic acids by using external stimuli is important for regulating biological processes and for the possibility of developing unique molecular machines. This account summarizes the development of external stimuli-responsive nucleic acids by our group. Our external stimuli-responsive nucleic acids are designed and synthesized through sugar, backbone, and nucleobase modifications. Various external stimuli, such as light, acids, or oxidants/reductants can trigger changes in nucleic acid structure. By means of such structural alterations, various properties of nucleic acid, including their hybridization ability, nuclease resistance, backbone degradability, and base-recognition ability, can be changed. 1 Introduction 2 External Stimuli-Responsive Nucleic Acids 2.1 2′,4′-Bridged Nucleic Acid Analogues Bearing External Stimuli-Responsive Bridged Moieties 2.2 Oligonucleotides Containing a P–N Phosphoramidite Linkage for Double-Stranded DNA-Templated Digestion 2.3 Light-Triggered Change in the Hydrogen-Bonding Pattern of a Nucleobase Analogue Enables a Strand-Exchange ­Reaction 3 Conclusions

The oxidation of alcohols using catalytic amounts of metal complexes is highly attractive from the viewpoint of green chemistry principles. However, examples of metal complex-catalyzed oxidations of alcohols with O2 using water as the solvent are still rare, and precious metals, high-pressure O2 or air, and a stoichiometric amount of base are often required. In this study, it was found that an oxovanadium-4,4′-t-Bubpy (4,4′-di-tert-butyl-2,2′-bipyridyl) complex exhibited high catalytic activity in the oxidation of benzhydrols under an atmosphere of O2 in water as the sole solvent. Interestingly, this catalytic oxidation method could be applied to the gram-scale aerobic oxidation of alcohols in water under the atmosphere.

LnCrAsO (Ln: La, Ce, Pr, Nd) is prepared by solid state reaction of stoichiometric mixtures of LnAs, Cr, and Cr2O3 (evacuated silica tube, 1273 K, 20 h).

It is crucial that the reaction is carried out in oxygen atmosphere to afford the products selectively.

This is the first example of a photoacid generator (PAG) synthesis via the introduction of arylethynyl units into the chromophore.

The intermediate aldehydes undergo direct cyclization to the ajacent isoprenyl substituent to give cyclopentane derivatives with moderate diastereoselectivity.

The reaction of a wide range of aldehydes with nitromethane is highly enantioselective with DAC.

Tartaric acid catalyzes the asymmetric addition of vinylboronates to N-acyl quinoliniums, affording highly enantioenriched dihydroquinolines. The catalyst serves to activate the boronate through a ligand-exchange reaction and generates the N-acyl quinolinium in situ from the stable quinoline-derived N,O-acetal.

The 1,3-amino sulfonamides efficiently promote the asymmetric addition of ZnEt2 to various aldehydes.

An inexpensive and environmentally benign method for the oxidation of benzyl alcohols is reported employing a vanadium catalyst and using water as reaction solvent under an atmospheric pressure of oxygen.

The control of molecular properties using external stimuli is an attractive research area that offers the potential for regulation of various biological phenomena. This review summarizes the concept, design, syntheses and properties of nucleic acid switches in response to external stimuli, namely, "external-stimuli-responsive bridged nucleic acids monomer". From (1)H-NMR experiments, every external-stimuli-responsive bridged nucleic acid monomer was found to have an N-conformation, while an S-conformation was predominantly observed after exposure to a proper stimulus. Each bridged nucleic acid monomer was effectively introduced into oligodeoxynucleotides using an automated DNA synthesizer. Moreover, oligonucleotides modified with these bridged nucleic acid monomer were changed in their hybridization property and tolerance to enzymatic digestion in response to each stimulus. These results clearly showed that external-stimuli-responsive bridged nucleic acids monomers should work as a nucleic acid switch, and have the potential for regulation of various biological phenomena.

Key steps of the described synthesis are the diastereoselective construction of a diaryl-substituted stereogenic center by an intramolecular Pd-catalyze α-C-arylation and subsequent direct conversion of the vinologous imid function into the C2-C25 double bond of haouamine B.

Both the reaction rate and the enantioselectivity are significantly improved upon in less polar solvents.

A novel nucleoside analogue (IV) with a disulfide bridge structure at the sugar moiety, which shows redox-responsive reversibility of the sugar conformation due to the formation and scission of the disulfide bond, is designed and synthesized.

Under optimized conditions concerning the solvent, additive, and catalyst loading butylammonium salt (I) in general is superior to its ethylammonium analogue in catalyzing the title reaction (diastereomers are not separated, d.e.

Treatment of 1-CH 3 B 5 H 8 or 2-CH 3 B 5 H 8 with P(CH 3 ) 3 resulted in the cleavage of the pentaborane framework to give CH 3 B 2 -H 3 •2P(CH 3 ) 3 , and B 3 H 5 •3P(CH 3 ) 3 . The methylated diborane(4) adduct CH 3 B 2 H 3 •2P(CH 3 ) 3 was characterized by mass and NMR spectroscopy, and its reaction chemistry was studied. Hydrogen chloride reacted with CH 3 B 2 H 3 •2P(CH 3 ) 3 to give BH 3 •P(CH 3 ) 3 and CH 3 BHCl•P(CH 3 ) 3

The chlorotriborane(7) (B 3 H 6 Cl) adduct of N(CH 3 ) 3 was formed by the reaction of B 4 H 8 •N(CH 3 ) 3 with HCl in dichloromethane or with HgCl 2 in chloroform. The reaction of B 3 H 7 •N(CH 3 ) 3 with BCl 3 in dichloromethane was found to be a better preparative method for B 3 H 6 Cl•N(CH 3 ) 3 . The BCl 3 treatment was employed to convert the N(CH 3 ) 2 H, N(CH 3 )H 2 , NH 3 , and S(CH 3 ) 2 adducts of B 3 H 7 into the corresponding adducts of B 3 H 6 Cl

C 13 H 20 O 5 cristallise dans P1 avec a=7,535, b=9,472, c=10,927 A, α=104,631, β=103,430, γ=109,130°, Z=2; affinement jusqu'a R=0,045. La structure cristalline a une conformation symetrique C 1 comme une «selle»: l'angle d'intersection entre les 2 liaisons doubles est de 148,3° et l'atome oxygene du carbonyl est en dehors des 2 plans des liaisons doubles

Cristallisation dans Ammm avec a=3,8402, b=3,8708, c=27,2309 A, Z=2; affinement jusqu'a R=0,0334. Les caracteristiques essentielles de la structure rapportees anterieurement sont confirmees. Cette etude ameliore la precision des parametres cristallins. La molecule est stœchiometrique, avec le site interchaine O(5) non occupe

The chlorofluorocarbon (CFC) treatment of protonated mordenite (HM) was carried out in a flow reactor under ordinary pressure, usually at 600C for 10 min using CCIF{sub 3} as a treatment agent. The mordenite structure was almost completely retained during the CFC treatment. Evidence for dealumination and surface fluorination was observed by XPS examination. Decrease of surface acidity, as seen by NH{sub 3-}TPD, accompanied the treatment. The function of HM as a catalyst for alkylations of benzene and alkylated or halobenzenes with methanol was greatly enhanced by the CFC treatment. In particular, the activity maintenance was remarkably improved. Thus, in the alkylations at 300C under the molar ratios of CH{sub 3}OH/Aromatic compound = 1 and W/F = 81.2 (for toluene) or 97.5 (for 1,2,4-trimethylbenzene (TBM)) g h/mol, the conversions at the initial stage of the run were increased from 27 to 65% (for toluene) and from 12 to 47% (for TMB) by CFC treatment of the Hm catalyst. In addition, the conversions of benzene and TMB were well maintained at about 60 and 40%, respectively, throughout the running time of 3 h in the reactions catalyzed by the treated HM, while the conversions of benzene and TMB rapidly decreased and becamemore » almost zero within 90 min in the reaction catalyzed by untreated HM.« less

Novel sesquiterpene-neolignans, eudesobovatos A (1) and B (2), eudesmagnolol (3), eudeshonokiols A (4) and B (5), clovanemagnolol (6), and caryolanemagnolol (7), have been isolated from the bark of Magnolia obovata. Their structures were elucidated to be sesquiterpenes (eudesmol, 4,4,8-trimethyltricyclo [6.3.1.02,5] dodecane-1,9-diol, and clovanediol) combined through ether bond with neolignans such as obovatol, honokiol, and magnolol on the basis of spectral data, degradation, and/or synthesis. Compounds 1, 6, and 7 were found to exhibit interesting neurotrophic activity on a neuronal cell culture system derived from fetal rat hemisphere.

Photocatalytic reactions of alkenes over TiO2-adsorbed water have been investigated. The products are hydrogenated molecules (CnH2n+2) formed by the addition of two H atoms to the π bond of the alkene (CnH2n, 2⩽n⩽ 4) and lower alkanes (CH4, Cn – 2H2n – 2 and Cn–1H2n) formed by the cooperative addition of an H atom and an OH radical to the π bond followed by decomposition. The photocatalytic isomerization of butenes by surface OH radicals is also observed. The generalized reaction mechanisms for these photocatalytic reactions have been postulated. The initial rate of formation of the hydrogenation product and the sum of the initial rates of formation of lower alkanes per amount of alkene adsorbed are proportional to kH and (kHkOH)1/2, respectively. Here, kH and kOH are rate constants for addition of H atoms and OH radicals to alkene in the vapour phase. For photocatalytic isomerizations, it is found that the isomerization of (E)-but-2-ene to but-1-ene (trans form) which has the same geometrical form is about twice as effective as that between (Z)-but-2-ene and but-1-ene and that the addition of OH to the C(1) position of but-1-ene prevents the isomerization to but-2-enes.

The ortho-lithiation of chiral N,N-dimethyl-1-phenylethylamine (1) followed by sulfenylation and oxidation of the resulting sulfides afforded chiral sulfoxides 3 and 4. Use of sodium perborate as the oxidant gave the highest de

A new cembranolide diterpene, 7-epidenticulatolide, was isolated from a soft coral, Lobophytum denticulatum. The structute was deduced spectroscopically and determined by X-ray crystallography.

A new type of silicon carbide having rodlike grains has been fabricated by hot-pressing or hot-pressing followed by hot isostatic pressing using SiC whiskers as the raw powder. Preliminary relationships between sintering conditions and microstructure and fracture toughness of the processed ceramics were established. Ceramics with relative density greater than 98% were prepared at temperatures of 2050°C or greater. The fracture toughness of these ceramics was better than that of ordinary SiC, and its maximum value was 7.3 MPa · m1/2. Grain pullout, grain bridging, and crack deflection were considered to be the main operative mechanisms which led to improved fractrue toughness.