Bidentate amidine ligands for nickel(0)-mediated coupling of carbon dioxide with unsaturated hydrocarbons

Novel bidentate amidines were designed and synthesized as easily available electron-donating N-ligands for Ni0-mediated coupling of carbon dioxide with alkynes or allenes, and high regioselectivity was achieved even for the carboxylation of aryl substituted internal alkynes.     

Stereostructure of a novel cytotoxic 18-membered macrolactone antibiotic FD-891

The absolute stereochemistry of FD-891, a novel cytotoxic 18-membered macrolactone antibiotic, was determined by a synthetic approach as well as X-ray diffraction of degradative derivatives. The absolute configuration of FD-891 turned out to be as shown above. The stable conformer of FD-891 was also discussed with respect to biological activity by comparison with the structurally related concanamycin A on the bases of molecular mechanics calculations. [structure: see text]     

On the refracted–reflected spectrally negative Lévy processes

We study a combination of the refracted and reflected Lévy processes. Given a spectrally negative Lévy process and two boundaries, it is reflected at the lower boundary while, whenever it is above the upper boundary, a linear drift at a constant rate is subtracted from the increments of the process. Using the scale functions, we compute the resolvent measure, the Laplace transform of the occupation times as well as other fluctuation identities that will be useful in applied probability including insurance, queues, and inventory management.     

A Two-Step Synthesis Of (±)-Blastmycinolactol Using Acylurea

A convenient synthesis of natural (±)-blastmycino-lactol from the aldol addition reaction of n-pentanoylurea and (±)-2-benzyloxypropionaldehyde is described.     

Gas analyzer for continuous monitoring of trace level methanethiol by microchannel collection and fluorescence detection

The highly odorous compound methanethiol, CH₃SH, is commonly produced in biodegradation of biomass and industrial processes, and is classed as 2000 times more odorous than NH₃. However, there is no simple analytical method for detecting low parts-per-billion in volume ratio (ppbv) levels of CH₃SH. In this study, a micro gas analysis system (μGAS) was developed for continuous or near real time measurement of CH₃SH at ppbv levels. In addition to a commercial fluorescence detector, a miniature high sensitivity fluorescence detector was developed using a novel micro-photomultiplier tube device. CH₃SH was collected by absorption into an alkaline solution in a honeycomb-patterned microchannel scrubber and then mixed with the fluorescent reagent, 4-(N,N-dimethylaminosulfonyl)-7-fluoro-2,1,3-benzoxadiazole (DBD-F). Gaseous CH₃SH was measured without serious interference from other sulfur compounds or amines. The limits of detection were 0.2 ppbv with the commercial detector and 0.3 ppbv with the miniature detector. CH₃SH produced from a pulping process was monitored with the μGAS system and the data agreed well with those obtained by collection with a silica gel tube followed by thermal desorption–gas chromatography–mass spectrometry. The portable system with the miniature fluorescence detector was used to monitor CH₃SH levels in near-real time in a stockyard and it was shown that the major odor component, CH₃SH, presented and its concentration varied dynamically with time.     

Sulfonyl-bridged oligo(benzoic acid)s: synthesis, X-ray structures, and properties as metal extractants

Sulfonyl-bridged oligo(benzoic acid)s 7 _n (n = 2–4) are prepared from the corresponding triflate esters (8 _n ) of sulfur-bridged oligophenols by palladium-catalyzed methoxycarbonylation of the triflate moieties, followed by hydrolysis of the resulting methyl esters, and subsequent oxidation of the sulfur bridges. X-ray analysis reveals that dimer 7 ₂ forms supramolecular zig-zag chains through intermolecular hydrogen bonds between the carboxy groups. As for the crystal of trimer 7 ₃ , two molecules are associated through two couples of intermolecular hydrogen bonds between terminal and central carboxy groups to form a cyclic dimer, which connects with two adjacent dimers with the remaining carboxy groups to construct an infinite columnar structure. Tetramer 7 ₄ adopts a monomolecular cyclic structure through intramolecular hydrogen bonds between the terminal carboxy groups, and a molecule connects with each of two adjacent molecules through two couples of intermolecular hydrogen bonds between inner carboxy and sulfonyl groups. Solvent extraction experiments reveal that the oligo(benzoic acid)s exhibit high extractability toward lanthanoid ions (Ln³⁺); the performance follows the order 7 ₄  ≈ 7 ₃  > 7 ₂ . Moderate extraction selectivity is observed for the extraction of Pr³⁺, Gd³⁺, and Yb³⁺ with 7 ₂ . X-ray crystallographic analysis of cluster [Tb₄L₄(H₂O)₆](Et₃NH)₄, which was prepared from 7 ₄ (H₄L) and Tb(NO₃)₃·6H₂O in the presence of Et₃N, reveals that no sulfonyl oxygens coordinate to the metal centers. This indicates that the high extractability of 7 ₄ originates from the electron-withdrawing nature of the sulfonyl function, which increases the acidity of two adjacent carboxy groups.     

Far-infrared spectroscopy by synchrotron radiation at the UVSOR Facility

At the UVSOR Facility, Institute for Molecular Science, the practical use of the synchrotron radiation as a far-infrared light source has started. A spectroscopic system has been constructed at the beam line BL6A1 of UVSOR storage ring, which covers the wavenumber region from 5 to 250 cm^–1. The cross sectional diameter of the light beam at the sample position is as small as 3 mm with the angular divergence of about 100 mrad. The system has been made mainly for the transmission and reflection measurements of small samples with small angular divergence by the use of the high brightness of the synchrotron radiation. Examples of observed transmission and reflectivity spectra are shown.     

Novel High Precision Optoelectronic Device Fabrication Technique Using Guided Fluidic Assembly

High precision assembly of laser diodes (LDs) on silicon wafer substrates for use in advanced optoelectronic devices is an important issue from a mass production point of view. An acceptable alternative to replace an obsolete pick and place flip chip bonding robotic technology with a simple, low cost and high speed technique is desired for industrial applications. We have investigated a novel assembling technique with micrometer order accuracy for LDs and other microchips. Its feasibility for rapidly assembling a large number of high power edge emitting LDs is practically demonstrated. A 150 $mUm thick nickel metal mask is used to confine as well as guide the unassembled LDs into the recesses by its restricted displacements. This technique is based on guiding the LDs within a suitable fluidic medium and the assembling process is performed in two steps: (i) coarse precision with a confinement mask to bring LDs near the recesses to achieve high assembling efficiency and (ii) fine precision due to the electrode patterns on the base surface of LDs, under fluidic as well as gravitational force. The assembly of 80 red LDs of the same size and of 40 pairs of red and infrared LDs of two different sizes is successfully demonstrated within less than ±2 $mUm precision and 100% efficiency in a few seconds after transferring them into a confinement mask region.