Imino ene-type reaction of enamines with N-sulfonylimines and application to diastereoselective synthesis of N-sulfonyl-1,3-diamines

Enamines react rapidly with N-sulfonylimines to afford imino ene-type adducts. The reaction proceeds even at −78 °C in the presence of acetic acid and shows high diastereoselectivity. Acid hydrolysis of imino ene-type products affords β-amino ketones, and reduction with NaBH₃CN furnishes N-sulfonyl-1,3-diamines with high diastereoselectivities. The stereochemistry of these transformations is considered based on transition state models.     

An application of computer image-processing and film replica technique to a nickel foil strain gage

The elastic stress of a specimen subjected to repeated loads is measured by a microscopic observation of slip-bands in nickel foil bonded to the surface of the specimen. The relation between the stress amplitude and the density of slip-bands in the foil is examined at various temperatures. An image-processing system using a personal computer is applied for an automatic measurement of the density of slip-bands in the bonded foil. The density of slip-bands replicated in a plastic film is also measured by the imageprocessing system, and it is in good agreement with the density of the original slip-bands. The peak stresses in grooved shafts under bending are measured using the nickel foil gage and the image-processing system. It is found that the results are satisfactority accurate.     

Synthesis of Layered-Structure LiFeO2

Abstract

LiFeO₂, with a layered rocksalt structure of α-NaFeO₂-type was prepared by ion exchange reaction from Na⁺ ion to Li⁺ ion using α-NaFeO₂. α-NaFeO₂-type LiFeO₂ was synthesized by using the mixture of LiI and KI in the temperature range 220 to 480 °C. The heat treatment temperature of 600 °C gave α-LiFeO₂-type LiFeO₂ as a main product. As a result of Rietveld analysis, the structure of LiFeO₂ which assigned to α-NaFeO₂-type by an XRD measurement, was the mixture of α-NaFeO₂-type and Li-intercalated spinel-type structures.     

Localization of heat in the shock compressed matter and its application to materials processing

Abstract

Both the heterogeneous deformation and the localization of heat in the shock compressed materials are supported by in situ measurements and textural observations. Additional shock-induced radiation measurements on diamond powder aggregates confirm such a current aspect and the proposed model, namely the skin model, that allows us to estimate quantitatively both the amount of localized heat and the subsequent thermal diffusion process. The parameter, ratio of the skin thickness to the cube size or particle size, is a convenient, universal parameter to representthe shock state of powder and is independent of particle size but dependent on shock pressures. The skin temperatures are approximately constant and equal to the melting temperature. The shock processing, especially shock consolidation of powders, effectively utilizes these phenomena and can be designed based on the skin model.     

Synthesis and absorption/emission properties of novel poly(silylenearylenevinylene)s

Polymerization of p-(dimethylsilyl)phenylacetylene in toluene at 25 and 80 °C with RhI(PPh₃)₃ catalyst afforded highly regio- and stereoregular poly(dimethylsilylene-1,4-phenylenevinylene)s [cis- and trans-poly( 1a )s] containing 98% cis- and 99% trans-vinylene moieties, respectively. The trans-type polymers exhibited redshifts and hyperchromic effects in the ultraviolet–visible spectrum as compared with the cis-type counterparts. Photoirradiation of cis- and trans-poly( 1a )s gave cis-rich mixtures at equilibrium states. The trans and cis polymers exhibited different emission properties, for example—trans polymer, emissn λ_max = 400 nm, quantum yield: 3.4 × 10⁻³ and cis polymer, emissn λ_max = 380 nm, quantum yield: 1.5 × 10⁻³. Besides poly( 1a ), poly(dimethylsilylenearylenevinylene)s containing biphenylene and phenylenesilylenephenylene units [poly( 3 )] were prepared. The extent of conjugation in these polymers decreased in the orders of biphenylene > phenylene > phenylenesilylenephenylene as well as trans-vinylene > cis-vinylene. The quantum yield of the trans-rich polymer with biphenylene moiety was fairly large and 0.15. Polyaddition of 1,4-bis(dimethylsilyl)benzene and three types of diethynylarenes (4,4′-diethynylbiphenyl, 2,7-diethynylfluorene, and 2,6-diethynylnaphthalene) catalyzed by RhI(PPh₃)₃ provided novel regio- and stereoregular polymers [poly( 6 )]. These polymers displayed blue light emission with high quantum yields (4–81%). © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3615–3624, 2003     

Molecular weight evaluation of poly(dimethylsiloxane) on solid surfaces using silver deposition/TOF-SIMS.

Molecular ions include information about end groups, functional groups and molecular weight. A method for the direct detection of these in the high mass range (m/z > 1000) from poly(dimethylsiloxane) (PDMS) on a solid surface was investigated. It was found that a TOF-SIMS analysis of silver-deposited surfaces (silver deposition/TOF-SIMS) is useful for this purpose. Using the silver-deposition/TOF-SIMS method, silver-cationized quasi-molecular ions were clearly detected from PDMS on solid surfaces, and their structure and molecular weight were evaluated. In addition, their images were observed without the interference of deposited silver. By applying to the analysis of paint defects etc., it was confirmed that this technique is useful to analyze actual industrial materials. Silver-cationized ions were detected not only from PDMS, but also from other organic materials, such as lubricant additives and oils on solid surfaces. Therefore, the silver deposition/TOF-SIMS method was proved to be useful for the analysis of ultrathin substances on solid surfaces.     

Lewis base-catalyzed conjugate reduction and reductive aldol reaction of alpha,beta-unsaturated ketones using trichlorosilane

Lewis bases such as Ph3P=O and HMPA catalyze the 1,4-reduction of alpha,beta-unsaturated ketones with trichlorosilane, and because the 1,2-reduction of aldehydes scarcely proceeded under the conditions, one-pot reductive aldol reactions with aldehydes were successfully achieved; preliminary studies using a chiral Lewis base revealed a high potential for enantioselective catalysis.     

Tubular gel fabrication and cell encapsulation in laminar flow stream formed by microfabricated nozzle array

We have used a laminar flow stream formed by a microfabricated nozzle array to prepare cell-encapsulated alginate gel micro-tubes, in which cells formed a cylindrical multi-cellular aggregate after cultivation for two weeks.     

Dynamic transition in the structure of an energetic crystal during chemical reactions at shock front prior to detonation

Mechanical stimuli in energetic materials initiate chemical reactions at shock fronts prior to detonation. Shock sensitivity measurements provide widely varying results, and quantum-mechanical calculations are unable to handle systems large enough to describe shock structure. Recent developments in reactive force-field molecular dynamics (ReaxFF-MD) combined with advances in parallel computing have paved the way to accurately simulate reaction pathways along with the structure of shock fronts. Our multimillion-atom ReaxFF-MD simulations of l,3,5-trinitro-l,3,5-triazine (RDX) reveal that detonation is preceded by a transition from a diffuse shock front with well-ordered molecular dipoles behind it to a disordered dipole distribution behind a sharp front.     

Efficient passively Q-switched Yb:LuAG microchip laser

An efficient passively Q-switched Yb:LuAG microchip laser with Cr4+:YAG as saturable absorber was demonstrated for the first time to our knowledge. Slope efficiencies of 40% and 28% were measured for the initial transmission of Cr4+:YAG, T(0)=95% and 90%, respectively. Laser pulses with a pulse energy of 19 microJ and a pulse width of 610 ps at the repetition rate of 12.8 kHz were achieved for T(0)=90%; the corresponding peak power of over 31 kW was obtained. The lasers oscillated at two or three longitudinal modes owing to the broad emission spectra of Yb:LuAG and mode selection by Cr4+:YAG thin plate acting as an intracavity etalon.