Assembly of a Benzo-Fused Bridged Ketone Scaffold from 1,5,10-Enediynes through One-Pot Ruthenium-Catalyzed Cyclization/Iodine-Mediated Oxidative Ring Expansion

In the presence of a cationic Ru catalyst, 1,6-diynes bearing a terminal styryl moiety underwent [2+2+2] cyclization to produce dehydrobiphenylenes fused with a five-membered ring. Although the cycloadducts were unstable toward purification, their one-pot iodine-mediated ring expansion successfully afforded unprecedented bridged ketone products containing a benzo-fused bicyclo[3.2.1] framework.     

n-Butyllithium-promoted regioselective elimination of vicinal bis-triflate having an adjacent ether oxygen

Regioselective elimination of a vicinal bis-triflate having an adjacent ether oxygen functional group has been developed. Considered in the context of our studies of the regioselective elimination of vicinal dibromide, the key to the mechanism involves the electron-withdrawing inductive effect of the neighboring oxygen functional group. Aliphatic vinyl triflate was shown to be effective in Suzuki–Miyaura cross coupling compared with corresponding aliphatic vinyl bromide.     

Ion-pair structure of vaporized ionic liquid studied by matrix-isolation FTIR spectroscopy with DFT calculations: a case of 1-ethyl-3-methylimidazolium trifluoromethanesulfonate

The matrix-isolation infrared spectrum of a thermally evaporated ionic liquid, 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([Emim][OTf]), was measured by FTIR spectroscopy and analyzed with the aid of DFT calculations. The main chemical species in the observed IR spectrum was mainly identified as the 1:1 cation-anion pair, which corresponds to the second stable ion-pair structure bonded through five hydrogen bonds between three O atoms of the anion side and four H atoms of the cation.     

Computation of the pressure on the surface of a fuselage with a wing in an ideal fluid

The flows around complex three-dimensional bodies by an ideal fluid are computed by methods [1–3] using approximation of the surface by a set of plane elements. A layer of surface singularities, whose intensity is found by solving a system of linear algebraic equations of very high order, is distributed continuously over each element. Evaluation of the system coefficients and its solution require significant machine time expenditures on powerful electronic computers. If in the method of [2] the total system of equations is separated successfully into several subsystems by simplifications and an approximate solution of the problem is obtained more rapidly than by the method in [1], then the same author practically used the method in [1] to design specific fuselages in [3]. A method [4] developed for a fuselage is expanded in this paper to design a wing-fuselage combination. This method turns out to be less tedious, without being inferior in accuracy, by being different from the method in [1] in the means of solving the fundamental integral equation.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 110–115, May–June, 1977.     

High-performance liquid chromatography with photodiode array detection for determination of nobiletin content in the brain and serum of mice administrated the natural compound

We recently demonstrated that nobiletin, a citrus flavonoid, exhibits anti-dementia action in animals. However, no determination methods for the content of nobiletin with beneficial action in the brain of nobiletin-administered animals have been developed, nor has its pharmacokinetics been revealed completely. Here, we established the high-performance liquid chromatography/photodiode array detection method for nobiletin determination using Bond Elut C18 SPE cartridges for extraction, where the calibration curve was linear over 0.025-10 ng, with coefficient of variation of less than 6.76%. This method enabled us to determine pharmacokinetic parameters of nobiletin given intraperitoneally or per os in the brain of mice.     

Microbial conversion of curcumin into colorless hydroderivatives by the endophytic fungus Diaporthe sp. associated with Curcuma longa

We investigated the microbial conversion of curcumin (1) using endophytic fungi associated with the rhizome of Curcuma longa (Zingiberaceae). We found that Diaporthe sp., an endophytic filamentous fungus, converts curcumin (1) into four colorless derivatives, namely (3R,5R)-tetrahydrocurcumin (2), a novel (3R,5S)-hexahydrocurcumin (3) named neohexahydrocurcumin, (3S,5S)-octahydrocurcumin (4) and meso-octahydrocurcumin (5).     

9-Azanoradamantane N-oxyl (Nor-AZADO): a highly active organocatalyst for alcohol oxidation

A highly active organocatalyst for alcohol oxidation has been developed. 9-Azanoradamantane N-oxyl (Nor-AZADO 4), constituting an unhindered, stable nitroxyl radical, exhibits superior catalytic activity to 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and AZADOs in the oxidation of alcohols to their corresponding carbonyl compounds.     

Hydrodynamic interpretation on the rotational diffusion of peroxylamine disulfonate solute dissolved in room temperature ionic liquids as studied by electron paramagnetic resonance spectroscopy

Rotational motion of a nitroxide radical, peroxylamine disulfonate (PADS), dissolved in room temperature ionic liquids (RTILs) was studied by analyzing electron paramagnetic resonance spectra of PADS in various RTILs. We determined physical properties of PADS such as the hyperfine coupling constant (A), the temperature dependence of anisotropic rotational correlation times (τ(∥) and τ(⊥)), and rotational anisotropy (N). We observed that the A values remain unchanged for various RTILs, which indicates negligible interaction between the N-O PADS group and the cation of RTIL. Large N values suggest strong interaction of the negative sulfonyl parts of PADS with the cations of RTILs. Most of the τ(∥), τ(⊥), and (τ(∥)τ(⊥))(1/2) values are within the range calculated on the basis of a hydrodynamic theory with stick and slip boundary conditions. It was deduced that this theory could not adequately explain the measured results in some RTILs with smaller BF(4) and PF(6) anions.     

Isomerization dynamics of the 2-phenylazo-1,3-dimethylimidazolium cation photoexcited to the S2 (π, π*) state as studied by transient absorption spectroscopy in the time domain of 10(-13) to 10(3) seconds

Photoinduced isomerization of a novel photochromic cation, [2PA-Mmim](+) (2-phenylazo-1,3-dimethylimidazolium cation), was studied by optical spectroscopic methods. The UV-Vis absorption spectra of the [2PA-Mmim](+) cation show two prominent bands starting around 410 and 520 nm, corresponding to the S(0)-S(2) (π, π*) and S(0)-S(1) (n, π*) transitions, respectively. The photoisomerization mechanism is studied by femtosecond time-resolved transient absorption experiments performed after S(0)-S(2) (π, π*) excitation in several solvents with different viscosity, including ionic liquids. The transient absorption signals at two representative wavelengths were fitted by bi-exponential functions, which yield four decay components. The photoisomerization mechanism is discussed in light of the relaxation schemes available for azobenzene. Only one of the components depends on the solvent viscosity and it changes from 1.2 ps (dichloromethane, 0.4 cP) to 5.6 ps ([Bmim][BF(4)], 93 cP). This component is assigned to a molecule at the S(1) state, which is responsible for the "rotational" isomerization. The weak dependence on the solvent viscosity of this component is explained in terms of local change in the viscosity as a result of local heating due to excess energy released at S(2)-S(1) internal conversion. The other three components of ～0.4, 1.0 and 10 ps are attributed to relaxation processes of the molecule at S(2), S(1) and S(0) states, respectively. The quantum yields for the forward E-Z photoisomerization are ～0.15 after S(2) excitation. The backward Z-E isomerization is slow with a lifetime of 1 hour and an activation energy of 91 kJ mol(-1) through an "inversion" mechanism.