One-pot reactions of bicyclic zinc enolate generated from Ni-catalyzed reductive cyclization to furnish octahydro-4,7-ethanobenzofuran-9-one derivatives

The one-pot reactions of catalytically generated bicyclic zinc enolate with various electrophiles are reported. The zinc enolate as a key intermediate is efficiently delivered from Ni-catalyzed reductive cyclization of alkynyl cyclohexadienone. Employing aldehydes, imine, nitroalkene, and α,β-unsaturated carbonyl compounds as electrophiles, this new class of one-pot reactions gave multi-functionalized cis-hydrobenzofurans and octahydro-4,7-ethanobenzofuran-9-one derivatives in moderate to good yields.     

Preparation of Aqueous Polyurethane Dispersions Using Aromatic Diisocyanate

Aqueous polyurethane dispersions were prepared by the reaction of hydroxyl-terminated poly(ethylene adipate), ethylene glycol, dimethylol propionic acid and aromaic diisocyante, 4,4′-diphenylmethane diisocyanate. The influence of molecular weight of oligoester and molar ratio between isocyanate and hydroxyl groups (NCO/OH) in the prepolymerization step were investigated. Molecular weight, particle size and particle size distribution were measured and compared. It was verified that the molecular weight increases with increasing in NCO/OH molar ratio. The results suggest that the hard segment content plays an important role in particle size and particle size distribution of the dispersions.     

Highly extended conformation of polyelectrolytes incorporated into hybrid threadlike micelles studied by small angle neutron scattering

SANS measurements revealed that polyelectrolytes, sodium salt of partially sulfonated polystyrenes, incorporated into enormously long hybrid threadlike micelles formed in aqueous solution with a cationic surfactant, cetyltrimethylammonium bromide, have a highly extended conformation with high confinement along the micelles with a radius of 2.3 nm.     

Ab initio study of field emission from graphitic ribbons

We have performed first-principles calculations on field emission (FE) from graphitic ribbons within the time-dependent density-functional theory. An important finding is that dangling bond states localized at clean edges are major contributors to FE current. H termination makes the FE current small due to the disappearance of the dangling-bond states. FE is found not to occur from the edge state of a H-terminated zigzag ribbon even when the state is at the Fermi level. The results of the FE current from graphitic ribbons give approximately 1 microA for maximum of FE current from a circular edge of graphitic sheets with approximately 1 nm diameter of an open-ended multiwalled carbon nanotube under a high electric field of approximately 1 V/A.     

Theory of resonant forbidden Raman scattering in semiconductors

The Raman tensors for the electric field-induced and wavevector dependent scattering from LO phonons in semiconductors have been calculated near critical points using a perturbation treatment. The resulting expressions have analytic closed forms such that the dependence of the forbidden scattering intensity on the incident photon energy and the applied d.c. electric field can be evaluated from available energy band parameters. The forbidden LO scattering intensity of GaAs in the back scattering configuration has been numerically calculated near the e₁ and E₁ gaps as functions of the incident photon energy and the dc electric field. The result shows strong interference between the two scattering processes. The allowed TO and LO Raman scattering intensities of GaAs were also calculated at a wavelength of 1.06 μm from the SHG and Faust-Henry coefficients, and compared with the forbidden LO intensity.     

Theoretical calculation of the reduced viscosity of aqueous suspensions of charged spherical particles

The origin of the variety of characteristics of the reduced viscosity of aqueous suspensions of charged spherical particles has been an unsolved problem. To solve the problem, the reduced viscosity due to interparticle electrostatic interactions between charged spherical particles are calculated as a function of particle concentration with scanning various parameters, such as diameter of particle, number of charges per particle, and added‐salt concentration. The result successfully reproduced the variety of characteristics. Of all the scanned parameters, the diameter of the particle has a significant role to display the variety of characteristics when other parameters are fixed. When the diameter is very small (～0 Å), the calculated reduced viscosity of aqueous suspensions of charged spherical particles increases with decreasing particle concentration and it shows a maximum. This behavior is very similar to the reduced viscosity of linear chain polyelectrolyte solutions. Whereas, when the diameter is large (>2000 Å), the calculated reduced viscosity decreases with decreasing particle concentration and it does not show a maximum. When the diameter is <1000 Å, the calculated reduced viscosity shows both the maximum and minimum. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 1068–1074, 2004     

Structure and synthesis of nectrisine, a new immunomodulator isolated from a fungus.

The structure of a novel immunomodulator, nectrisine (1), has been elucidated on the basis of chemical and spectroscopic evidence. Its absolute stereochemistry was predicted on the basis of the dibenzoate chirality rule and finally confirmed by a synthesis from D-glucose.     

Chelating of titanium by lactic acid in the water-soluble diammonium tris(2-hydroxypropionato)titanate(IV)

Stable water-soluble diammonium tris(2-hydroxypropionato)titanate(IV) [ammonium trilactatotitanate(IV)], (NH4)2[Ti(C3H4O3)3], was prepared in the crystalline form. According to the X-ray single-crystal diffraction data, this compound crystallizes in the cubic cell with a = 11.649(4) angstroms, space group P2(1)3 (no. 198), and has Z = 4 molecules per unit cell. The 13C NMR data and Raman and IR spectra support the determined structure. The absence of nonbonded functional groups restricts the formation of oligomers in contrast to the reported speciation of citratoperoxotitanate(IV) complexes.