Catalytic cross-coupling reaction of esters with organoboron compounds and decarbonylative reduction of esters with HCOONH4: a new route to acyl transition metal complexes through the cleavage of acyl-oxygen bonds in esters

The Ru3(CO)12-catalyed cross-coupling reaction of esters with organoboron compounds leading to ketones is described. A wide variety of functional groups can be tolerated under the reaction conditions. Aromatic boronates function as a coupling partner to give aryl ketones. Acyl-alkyl coupling to dialkyl ketones is also achieved by the use of 9-alkyl-9-BBN in place of boronates. The Ru3(CO)12-catalyzed decarbonylative reduction of esters with ammonium formate (HCOONH4) leading to hydrocarbons is also described. No expected aldehydes are produced, and controlled experiments indicate that aldehydes are not intermediate for the transformation. A hydrosilane can also be used as a reducing reagent in place of HCOONH4. A wide variety of functional groups are compatible for both reactions. The key step for both catalytic reactions is the directing group-promoted cleavage of an acyl carbon-oxygen bond in esters, leading to the generation of acyl transition metal alkoxo complexes.     

A simple but remarkably effective device for forming the C8-C14 polycyclic ring system of halichondrin B

A simple device consisting of two ion-exchange columns, two alumina-based filters, and a pump (Figure 1) was assembled to form the C8-C14 polycyclic ring system present in the halichondrin B class of marine natural products. The effectiveness of this device was tested for three substrates. In each case, the desired polycyclic ketal 3, 5, or 7 was obtained almost quantitatively in a single operation.     

Fe/Cr- and Co/Cr-mediated catalytic asymmetric 2-haloallylations of aldehydes

The first example to couple aldehydes and 3-bromo-2-halopropenes in a catalytic asymmetric manner is reported. The coupling reaction is effected by the use of a chiral sulfonamide-Cr complex (prepared in situ from 1d, CrBr3, Fe(III) or from Co(II), Et3N, and Mn), TMSCl, and 2,6-lutidine. The method reported here is operationally simple and scalable, furnishing 3-halohomoallylic alcohols with a synthetically useful level of enantiomeric excess.     

Synthesis of Light-emitting Silicon Nanoparticles by Intense Pulsed ion-beam Esvaporation

Synthesis of photoluminescent Si nanoparticles has been successfully prepared using an intense pulsed ion-beam evaporation (IBE) technique in vacuum. Si nanoparticles are produced by the IBE method without any post-annealings. Photoluminescence (PL) mainly in blue range with a peak of 455 nm and a shoulder near 510 nm is observed in as-deposited Si nanoparticles at room temperature. The blue light emission is relatively stable with no noticeable change, as the samples have already stored in air more than 4 months. The observed PL does not fit the quantum confinement model, since a majority of particle size is around ~20 nm, estimated by SEM and XRD measurements. Moreover, hydrofluoric acid (HF) corrosion tests on the Si nanoparticles also indicate a correlation between the presence of the surface oxide layers and the PL. Oxide-related luminescence is likely the source of this blue light emission.     

Forensic neutron activation analysis the Japanese scene

The progress of forensic neutron activation analysis (FNAA) in Japan is described. FNAA began in 1965 and during the past 20 years many cases have been handled; these include determination of toxic materials, comparison examination of physical evidences (e.g., paints, metal fragments, plastics and inks) and drug sample differentiation. Neutron activation analysis is applied routinely to the scientific criminal investigation as one of multielement analytical techniques. This paper also discusses these routine works.     

Complete stereochemistry of tetrafibricin

With use of the NMR databases in achiral and chiral solvents, the complete stereochemistry of tetrafibricin (1) has been elucidated without degradation of the carbon framework. [structure--see text]     

All-Fiber Ultra-Fast Switching Using Stimulated Raman Scattering

We propose a method for all-fiber ultra-fast switching using stimulated Raman scattering. It is based on the transference of energy from the signal as pump to the control signal as first Stokes by stimulated Raman scattering. In the absence of a control signal, the transference of energy from the pump signal to the generated first Stokes is negligible, which results in high output power at the pump signal wavelength. To minimize the walk-off problem between two wavelengths, we chose pump signal and control signal to be equally spaced on opposite sides of the zero dispersion wavelength of the fiber. Based on this assumption, the all-fiber ultra-fast optical switch with low power consumption and high output extinction ratio can be realized.     

Reductive ring openings of allyl-alcohol epoxides

Red-Al reduction of allyl-alcohol epoxides was shown to yield 1,3-diols in high regioselectivity, while DIBAL reduction was shown to yield 1,2-diols.