Stereodivergent and reiterative synthesis of bistetrahydrofuran ring cores of annonaceous acetogenins

Eight diastereoisomers of the bistetrahydrofuran ring cores of annonaceous acetogenins have been synthesized by asymmetric alkynylation of alpha-tetrahydrofuranic aldehydes and stereodivergent one-pot tetrahydrofuran (THF) ring formation. In all cases, the asymmetric alkynylation proceeded with very high diastereoselectivity to give eight kinds of optically pure THF cores. We also describe a comparison of the (1)H and (13)C NMR spectral data of the eight isomers and give full details of the THF ring construction.     

Polyimides derived from bismethylolimides. II. Polyamine-imides from bismethylolimides and diamines

Compounds in the N-methylolimide group reacted smoothly with amines in the presence of water to yield the corresponding condensation products. Polycondensations of bismethylolimides, N,N′-bismethylolpyromellitic diimide, and N,N′-bismethylolbenzophenonetetracarboxylic diimide, with amines such as aromatic diamines, piperazine, and n-butylamine, were carried out in DMAc that contained 1% water to produce linear polyamine-imides. The polyamine-imides assumed various colors, from very pale yellow to deep purple, and had inherent viscosities in the 0.07–0.37-dl/g range. Most of these polymers were soluble in polar solvents such as DMAc and DMSO. The thermal stability of the polymers was examined by thermogravimetric analysis; decomposition started at 210–350°C and weight residue at 500°C was 22–85% in air.     

Self-assembly and luminescence of oligo(p-phenylene vinylene) amphiphiles

We have synthesized a series of amphiphilic molecules consisting of oligo(phenylene vinylene) (OPV) asymmetrically end-substituted with a hydrophilic poly(ethylene glycol) (PEG) segment and a hydrophobic alkyl chain. This amphiphilic structure induces self-assembly into both thermotropic and lyotropic lamellar liquid crystalline (LC) phases. The molecules form strongly fluorescent, self-supporting gels in both water and polar organic solvents, even at high concentrations on the order of 30 wt %. These self-assembled structures have been characterized by small-angle X-ray scattering (SAXS), differential scanning calorimetry (DSC), and polarized optical microscopy (POM). Photoluminescence (PL) is influenced by the structure of the material, with enhanced emission in the LC state due to assembly of the chromophore in confined two-dimensional layers. Self-assembly controlling molecular aggregation at the nanoscale could significantly improve the performance of OPV-based materials in optoelectronic devices.     

Structures of chlorotrimethylstannane Sn/CH3/3Cl dispersed in various matrices

The structure of chlorotrimethylstannane was studied by Mössbauer spectroscopy in solids, frozen solution, and argon matrices at low temperatures. In frozen solutions, quadrupole splitting was very similar to the value in solid phase, and strong intermolecular interaction may exist between Sn/CH₃/₃Cl and solvent molecules. In argon matrices, the quadrupole splitting of Sn/CH₃/₃Cl was much smaller. Comparison of the observed quadrupole splitting with the predicted value based on the point charge model suggests that the Sn/CH₃/₃Cl molecule may have a tetrahedral structure and be isolated well from each other in the argon matrix.     

The synthesis of naphtho[1,2-b]thiophene and all of the eight isomers of monomethylnaphtho[1,2-b]thiophene

The synthesis of naphtho[1,2-b]thiophene and all of the eight monomethylnaphtho[1,2-b]thiophene isomers is described.     

Polarized ethylene. V. Synthesis of 1-substituted indolizine,pyrazolo[1,5-a]pyridine,and their related compounds using methoxyethylene derivatives

The reaction of pyridinium or isoquinolinium N-ylides with methoxy-substituted ethylenes gave the corresponding indolizine and pyrrolo[2,1-a]isoquinoline derivatives bearing acetyl, aroyl, cyano, ester group at the 1-position in one step. Pyrazolo[1,5-a]pyridine, pyrazolo[1,5-a]quinoline, and pyrazolo[5,1-a]isoquinolines were also synthesized in good yields from the corresponding aromatic N-imines and methoxyethylene derivatives.     

Mössbauer study on tris(1,10-phenanthroline) iron(II) ion synthesized in zeolite Y and its pyrolysis products

Tris(1,10-phenanthroline) iron(II) ([Fe(phen)₃]²⁺) ion synthesized in the supercage of zeolite Y has been characterized by Mössbauer, UV-VIS reflectance, and X-ray diffraction methods. The complex in the supercage may be significantly distorted by interaction between the complex and the supercage wall. Pyrolysis mechanism under air of the complex in the supercage was studied on the basis of Mössbauer spectra.     

A119Sn-Mössbauer study of tetramethylstannane isolated in low temperature argon matrix

Unusually broad¹¹⁹Sn-Mössbauer absorption was observed in pure Sn(CH₃)₄ or Sn(CH₃)₄/argon condensed at low temperatures by pulsed deposition. Such broadening of the Mössbauer linewidth suggested the presence of large quadrupole splitting due to possible distortion of molecular structure as deposited in the argon matrix.     

Neutron activation analysis of rare earth elements in alered volcanic rocks /palagonite/ from a seamount

By means of INAA, REEs in the dredged rocks from a seamount /KH73-4-2/ in the East Mariana Basin were determined. Based on the REE patterns, the rocks are classified into two groups despite of alteration: highly altered palagonite of oceanic-island tholeiitic nature, and relatively fresh basaltic-andesitic rocks of alkaline rock nature.     

Enantioselective construction of biaryl part in the synthesis of stegane related compounds

A Pd-mediated intramolecular aryl-aryl coupling reaction of phenyl benzoate derivatives were examined to form benzo[c]chromen-6-ones, and then enantioselective lactone-opening reaction with a borane-oxazaborolidine combination was carried out. The resulting biphenyl was transformed into a key intermediate for the stegane related compounds. The absolute configuration of the biphenyl is also discussed.