Stereoselective Synthesis of (Z)-α,β-Unsaturated Ketones via Hydromagnesiation of Alkynylsilanes

α,β-Unsaturated ketones are important synthetic intermediates because of their versatile reactivities and many syn-thetic applications of them have been reported in the literature.[1] However, only a few methods for the synthesis of (Z)-α,β-unsaturated ketones are available. The palladium catalyzed coupling reactions of alkenyl copper reagents with acid chlorides afforded (Z)-α,β-unsaturated ketones.[2] The phase transfer catalyzed hydroacylation of allenes with carbon monoxide, decacarbonyldimanganese and methyl iodide gave (Z)-α,β-unsaturated ketones in a stereospecific process.     

Highly sensitive voltammetric biosensor for nitric oxide based on its high affinity with hemoglobin

Although heme protein-based, amperometric nitric oxide (NO) biosensors have been well documented in previous studies, most have been conducted in anaerobic conditions. Herein we report a novel hemoglobin-based NO biosensor that is not only very sensitive but also usable in air. The heme protein was entrapped in a sodium montmorillonite film, which was immobilized at a pyrolytic graphite electrode surface. Film-entrapped hemoglobin can directly exchange electrons with the electrode, and this process has proven to favor the catalytic reduction of oxygen. In addition, NO induced a cathodic potential shift of the catalytic reduction peak of oxygen. This potential shift was proportional to the logarithm of NO concentration ranging from 4.0 × 10⁻¹¹ to 5.0 × 10⁻⁶ mol/L. The detection limit has been estimated to be 20 pM, approximately four orders lower than previously reported amperometric detectors.     

The first 1-alkyl-3-perfluoroalkyl-4,5- dimethyl-1,2,4-triazolium salts

Syntheses of quaternary 1-alkyl-3-perfluoroalkyl-4,5-dimethyl-1,2,4-triazolium iodides have led to a variety of new quaternary salts via metathesis reactions. 1,4,5-Trimethyl-3-trifluoro-methyl-1,2,4-triazolium iodide (6) with LiN(SO(2)CF(3))(2), KSO(3)CF(3), AgClO(4), AgBF(4); 1-(3-fluoropropyl)-3-trifluoromethyl-4,5-dimethyl-1,2,4-triazolium iodide (7) with LiN(SO(2)CF(3))(2); and 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium iodide (8) with LiN(SO(2)CF(3))(2), AgClO(4), AgBF(4) gave excellent yields of new thermally stable and relatively low melting quaternary salts. The structure of 1,4,5-trimethyl-3-perfluorooctyl-1,2,4-triazolium tetrafluoroborate (11c) was confirmed by single-crystal X-ray analysis. Although the molecular weight of 11c (cation) is 3-fold greater than that of the 3-trifluoromethyl derivative 9d, its melting point is 32 degrees C lower.     

Fire retardant synergism between melamine and triphenyl phosphate in poly(butylene terephthalate)

The fire retardant efficiency of melamine (MA) and triphenyl phosphate (TPP) in poly(butylene terephthalate) (PBT) was studied by the limiting oxygen index (LOI) and the UL94 test. On adding 10 wt. % MA and 20 wt. % TPP, LOI increased from 20.9 to 26.6 and the UL94 V-0 rating was achieved. SEM and DSC analyses show that the fire retardants are compatible with PBT and facilitate crystallization of PBT. The occurrence of an interaction between MA + TPP and PBT was elucidated by TGA, dynamic FTIR, and pyrolysis/GC/MS. MA + TPP changes the degradation path of PBT and modifies the compositions of the gas and condensed-phase products.     

(Z)‐1‐Ferrocenyl‐3‐(3‐hydroxy­anilino)­but‐2‐en‐1‐one and (Z)‐1‐ferrocenyl‐3‐(4‐hydroxy­anilino)­but‐2‐en‐1‐one

The title compounds, both [Fe(C₅H₅)(C₁₅H₁₄NO₂)], crystallize with Z′ = 2 in the centrosymmetric space group P. In each compound, there is an intra­molecular N—H⋯O=C hydrogen bond, and pairs of inter­molecular O—H⋯O=C hydrogen bonds link the mol­ecules into chains, parallel to [10] in the 3‐hydr­oxy compound and parallel to [10] in the 4‐hydr­oxy compound.     

Preparation and Characterization of Ultrafine Rare Earth Molybdenum Complex Oxide Particles

Ultrafine rare earth molybdenum (La–Mo and Ce–Mo) complex oxide particles have been synthesized by the sol–gel process using citric acid as complexing agent. The influence of preparation conditions such as thermal treatment temperature (T), molar ratio of citric acid to metallic ions (L/M), and pH value of the starting solution on the oxide particle size has been studied. The formation of La₂Mo₂O₉and Ce₂Mo₃O₁₂has been investigated using XRD, DTA–TG, FT-IR, TEM, and BET surface area measurements. It is shown that the morphology and structure of the oxide particles are significantly dependent on the preparation conditions. The influence of different preparation methods on the particle size of La–Mo and Ce–Mo oxides is also discussed.     

Determination of capsaicinoids in salsa by liquid chromatography and enzyme immunoassay

Two simple and rapid methods were developed to monitor pungency of salsa in production. Capsaicin (C) and dihydrocapsaicin (DHC) were quantitated in 17 commercially available tomato-based salsas by enzyme immunoassay (EIA) and liquid chromatography (LC) with fluorescent detection. Samples were extracted with methanol and the extracts were subjected to solid-phase extraction (SPE) using polystyrene-divinylbenzene columns. Analysis of SPE eluates showed good correlation (r2 = 0.953) between LC and EIA, with a slightly high bias for EIA. Salsa fortified with C and DHC from 0.118 to 103.2 microg/g resulted in recoveries of 90-112% (C) and 76-97% (DHC). Limits of detection by LC were 0.1 microg/g for each capsaicinoid and 0.1 microg/g by EIA for total capsaicinoids. The LC on-column response was linear from 0.2 to 100 ng for both C and DHC, whereas the working range for EIA was 0.1-2.0 ppm. Pungency varied between different salsa brands labeled mild, medium, and hot.     

Immobilization of antibody fragment for immunosensor application based on surface plasmon resonance

Biosurface fabrication using the Fab′ fragment of immunoglobulin (IgG) was carried out by self-assembly (SA) technique. The pepsin-digested monoclonal antibody (Mab) against bovine insulin containing the F(ab′)₂ fragment and residual proteins was separated using affinity chromatography and dialysis. To prevent the nonspecific binding of F(ab′)₂ onto gold (Au) substrate, the native disulfide bridge was reduced using dithiothreitol (DTT) to convert F(ab′)₂ into Fab′, which made the immobilization to be carried out via the native thiol (–SH) group. The fabricated biosurface using SA technique showed the formation of stable thin film through AFM topography. Through the concentration change of DTT and Fab′, the absorption characteristics against the Au surface were investigated using surface plasmon resonance (SPR) with the flow cell. The amount of immobilized antibody fragment and the antigen binding capacity were regulated with respect to the reduction state and concentration of F(ab′)₂. Based on the biosurface of the fabricated Fab′, the insulin-detection was carried out by the measurement of SPR. The proposed antibody surface could successfully detect the bovine insulin at the concentration from 100 ng/mL to 10 μg/mL.     

Self－assembly of Novel Hetero[3]rotaxane, [2]Rotaxanes and [2]Catenane

One linear template 13 and one cyclophane template 15, both incorporating two electron rich 1,4‐dialkoxybenzene units and one diamide unit, have been synthesized. By utilizing donor‐acceptor interaction and/or intermolecular hydrogen bonding assembling principles, one novel hetero[3]rotazane 22·4Cl, possessing one neutral and one tetracationic ring components, has been synthesized from 13, through neutral [2]rotaxane 21 as intermediate. With 15 as template, tetracationic [2]catenane 23·4PF₆ was assembled by using donor‐acceptor interaction, but no neutral [2]rotaxane could be obtained under the typical conditions of hydrogen bonding assembling principle. The interlocked supramolecular compounds have been characterized and their spectral properties are investigated.     

Dispersed fluorescence spectroscopy of jet-cooled HCF and DCF: Vibrational structure of the X 1A' state

We recorded dispersed fluorescence (DF) spectra following excitation of the pure bending levels 2(0) (n) and the combination states 1(0) (1)2(0) (n) and 2(0) (n)3(0) (1) in the A 1A"<--X 1A' system of HCF and DCF. Spectra were measured with a 0.3 m spectrograph equipped with a gated intensified charge coupled device (CCD) detector and obtained under jet-cooled conditions using a pulsed discharge source. The DF spectra reveal rich detail concerning the vibrational structure of the X state up to 10 000 cm(-1). For HCF, resonances among the nearly degenerate levels 1(1)2n, 2n+13(1), and 2n+2 produce a polyadlike structure in the spectrum, and the usual effective spectroscopic Hamiltonian (Dunham expansion) poorly reproduces the experimental term energies. In contrast, this Hamiltonian works well for the term energies of DCF. Density functional calculations of the ground state vibrational frequencies were performed; the results are in excellent agreement with the experimentally derived vibrational parameters. The search for perturbations involving the low-lying a 3A" state is described.