Characterization of NIES CRM No. 23 Tea Leaves II for the determination of multielements

A candidate environmental certified reference material (CRM) for the determination of multielements in tea leaves and materials of similar matrix, NIES CRM No. 23 Tea Leaves II, has been developed and characterized by the National Institute for Environmental Studies (NIES), Japan. The origin of the material was tea leaves, which were ground, sieved through a 106-μm mesh, homogenized, and then subdivided into amber glass bottles. The results of homogeneity and stability tests indicated that the material was sufficiently homogeneous and stable for use as a reference material. The property values of the material were statistically determined based on chemical analyses by a network of laboratories using a wide range of methods. Sixteen laboratories participated in the characterization, and nine certified values and five reference values were obtained. These property values of the candidate CRM, which are expressed as mass fractions, were close to the median and/or mean values of the mass fractions of elements in various tea products. The candidate CRM is appropriate for use in analytical quality control and in the evaluation of methods used in the analysis of tea and materials of similar matrix.     

Photochemical intramolecular cyclization of o-alkynylaryl isocyanides with organic dichalcogenides leading to 2,4-bischalcogenated quinolines

When a mixture of o-alkynylaryl isocyanides and organic dichalcogenides such as diselenides or ditellurides was irradiated with light of wavelength over 300 or 400 nm, the intramolecular cyclization of the isocyanides took place to afford the corresponding 2,4-bischalcogenated quinolines selectively. The photochemical cyclization of 2-(phenylethynyl)phenyl isocyanide could also proceed in the presence of hydrogen transfer reagents such as tris(trimethylsilyl)silane, tributylgermyl hydride, alkanethiols, and benzeneselenol, providing the corresponding 3-phenylquinoline as the result of 2,4-dihydrogenation.     

Phenylenebis(ethynyl)-tethered bis-BINOL ligands for enantioselective catalyst based on dimeric TiIV aggregate

Bis-BINOLs 7a-c in which two BINOL units are tethered by phenylenebis(ethynyl) groups react with titanium tetraisopropoxide (2 equiv) to form intramolecular dimeric titanium(IV) aggregates 2a-c. Of these, 2a,b with an o-phenylenebis(ethynyl) tether are stable in the presence of excess titanium tetraisopropoxide. Complex 2a exhibits a relatively high enantioselectivity in asymmetric addition of diethylzinc to an aldehyde. [structure: see text]     

Reduction of carbonyl compounds via hydrosilylation : I. Hydrosilylation of carbonyl compounds catalyzed by tris(triphenylphosphine)chlororhodium

The hydrosilylation of various carbonyl compounds such as simple aldehydes, simple ketones, α,β-unsaturated carbonyl compounds, α-diketones, acyl cyanides and ketones having an electron-withdrawing group on the α-carbon using tris(triphenylphosphine)chlororhodium as a catalyst is described. Solvolysis of these silyl ethers and silyl enol ethers afforded the corresponding reduced products. The hydrosilylation of α,β-unsaturated carbonyl compounds was found to proceed by 1,4-addition. An oxidative adduct of triethylsilane to the rhodium-(I) complex was obtained as a reaction intermediate. The structure of the adduct was discussed on the basis of its IR and far-IR spectra.     

Salvileucalin B, a novel diterpenoid with an unprecedented rearranged neoclerodane skeleton from Salvia leucantha Cav

Salvileucalin B (2), having an unprecedented rearranged neoclerodane skeleton, was isolated from the aerial parts of Salvia leucantha Cav. (Labiatae) along with salvileucalin A (1). The absolute structures were elucidated by spectroscopic analysis, X-ray crystallographic analysis, and vibrational circular dichroism. Compound 2 represents a novel neoclerodane, characterized by a tricyclo[3.2.1.0 (2,7)]octane substructure incorporating the exocyclic C-20 methylene of 1. This molecule exerted cytotoxic activity against A549 and HT-29 cells with IC50 values of 5.23 and 1.88 microg/mL, respectively.     

Spin-density matrix elements for γp→K*0Σ+ at Eγ=1.85-3.0 GeV with evidence for the κ(800) meson exchange

The exclusive reaction γp→K(+)π(-)Σ(+) was measured for the first time using linearly polarized photons at beam energies from 1.85 to 2.96 GeV. Angular distributions in the rest frame of the K(+)π(-) system were fitted to extract spin-density matrix elements of the K(*0) decay. The measured parity spin asymmetry shows that natural-parity exchange is dominant in this reaction. This result clearly indicates the need for t-channel exchange of the κ(800) scalar meson.     

Synthesis and properties of a dithiirane trans-1,2-dioxide, a three-membered vic-disulfoxide

cis- and trans-3-(1-adamantyl)-3-tert-butyldithiirane 1-oxides were oxidized with dimethyldioxirane to give the trans-1,2-dioxide. Thermal decomposition of the 1,2-dioxide yielded the corresponding (E)- and (Z)-sulfines, thioketone, and cis- and trans-dithiirane 1-oxides. In the thermolysis, decomposition to the sulfines and SO was the main path and that to the thioketone and SO(2) was the minor one. The two decomposition processes and epimerization to the cis-1,2-dioxide were analyzed theoretically. SO generated in situ reacted with thioketones as additives to give the corresponding dithiirane 1-oxides.     

Photoinduced intramolecular cyclization of o-ethenylaryl isocyanides with organic disulfides mediated by diphenyl ditelluride

Photoinduced reaction of o-ethenylaryl isocyanides with organic disulfides in the presence of diphenyl ditellurides affords the corresponding bisthiolated indole derivatives via a radical cyclization process. The cyclization can proceed at room temperature upon visible-light irradiation and exhibits good tolerance to functional groups. Several organic disulfides also can be employed for this cyclization, and the corresponding bisthiolated indole derivatives are obtained selectively. In addition, the photoinduced reaction of o-ethenylaryl isocyanides with bis(2-aminophenyl) disulfide affords tetracyclic compounds in one portion.     

Asymmetric alkylation of aldehydes catalyzed by novel dinuclear bis-BINOLate titanium(IV) complexes

Bis-BINOLs 1a,b in which two BINOL units are tethered by o- and m-phenylenebis(ethynyl) groups form stable dinuclear bis-BINOLate titanium(IV) complexes 2a,b by treatment with titanium tetraisopropoxide. In the presence of excess titanium tetraisopropoxide, 2a and 2b (2–20 mol %) catalyze diethylzinc addition to aromatic and aliphatic aldehydes in an efficient manner to give the ethylation products with high enantioselectivities. While more than 1 equiv of titanium tetraisopropoxide (with respect to a substrate aldehyde) is generally employed for obtaining high turnover frequency and selectivity in reactions catalyzed by a parent (BINOLate)Ti(OⁱPr)₂, the amount can be reduced as low as 0.2 equiv in the reactions catalyzed by 2a,b.