Synthesis and properties of 1-(6-methoxy)-2-benzothiazolyl)-2-pyridones

Substituted ]-(6-methoxy-2-benzothiazolyt)-2-pyridones were prepared from 2-amino-6-methoxybenzathiazate through N-(6-methoxy-2-benzothiazotyl) cyanvorearmileaznd-3-aryl-N-(6-methoxy-2-benzothiazolyt)-2-cyano-2-propenamides. The cyclization of the latter with malonodinitrile in the presence of piperidine gave the corresponding pyridones. The structures of the synthesized compounds were confirmed by¹H NMR and mass spectral data.Department of Organic Chemistry, Mass Spectrometry Laboratory, Slovak Technical University, 812 37 Bratislava, Slovakia. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1402–1404, October, 1995. Original article submitted August 24, 1995.     

A theoretical study of the formation of the parent phosphinine C5H5P from the flash vacuum thermolysis of diallylvinylphosphine

The gas-phase decomposition of diallylvinylphosphine 1 into C5H5P 12 is studied by DFT/6-311+G(d,p) calculations with the B3LYP functional, followed by single-point energy-only calculations at the CCSD(T)/6-311+G(d,p) level. According to these calculations, the first step involves a retro-ene elimination that yields 3-phosphahexatrienes 2Z and 2E. Both compounds equilibrate through the formation of 1,2- and 3,4-dihydrophosphetes 3 and 4, and it is shown that the formation of 2Z is favored by the exothermic formation of the 3,4-dihydrophosphinine 5 through a 6pi-electrocyclization. Though 5 can easily isomerize into 2,3- (6) and 1,2-diyhydrophosphinines (7) by successive 1,5-hydrogen shifts, the formation of 12 from 5, 6, or 7 through an elimination of H2 is found to be a high energy process. It is also shown that the elimination of H2 from lambda5-phosphinine 8 following a C2v pathway is a symmetry-forbidden process. Finally, 1,4-dihydrophosphinine 9, which can be formed through a 1,4-hydrogen shift from lambda5-phosphinine 8, is found to be a convenient precursor of 12 through a 1,4-elimination of H2. The formation of 9 from 5 involves the intermediary formation of 3-phosphabicyclo[3.1.0]hex-2-ene 10. The mechanism eventually proposed for the formation of 12 from 2Z is given in Scheme 16 at the CCSD(T) level.     

Carbon-carbon coupling constants - a new guide in the stereochemistry of oximes

A positive contribution of more than 7 Hz to the direct ¹³C-¹³C spin-spin coupling constants induced by the proximity of the nitrogen lone pair in syn-orientation to the coupled nuclei allows an unambiguous configuration assignment of diverse oximes.     

Amperometric flow-injection method for the assay of l-ascorbic acid based on the photochemical reduction of Methylene Blue

Ascorbic acid (AA) is determined by amperometric detection based on the photochemical reduction of Methylene Blue (MB(+)) in 0.1 M phthalate buffer at pH 3.8. In this medium, MB(+) using flow-injection analysis. The carrier stream is 1 mM MB(+) is reduced quasi-reversibly at a glassy carbon electrode at -0.34 V vs. Ag/AgCl, while AA is oxidized irreversibly at about 0.3 V. The reactor is irradiated with a 500 W halogen lamp to facilitate the development of the photochemical reaction. A laboratory-built wall-jet electrode system was used. The Leucomethylene Blue formed in the reaction is detected at +0.050 V. At 2.2 ml min(-1) and using a sample loop of 43 mul, the method allows the determination of AA in the range 5.0-90.0 mug ml(-1), with a relative standard deviation of 1.3-4.8%, a detection limit of 1.9 mug ml(-1) and a sampling frequency of 45-50 h(-1).     

Immobilization of protein on ferromagnetic Dacron

Ferromagnetic Dacron (polyethyleneterephthalate) is proposed as a matrix to immobilize proteins covalently. Dacron in powder was magnetized by reacting ferrous (Fe+2) and ferric (Fe+3) ions with its hydrazide form at pH 8.3. Ferromagnetic hydrazide Dacron was converted to ferromagnetic azide Dacron and amyloglucosidase (E.C. 3.2.1.3) was covalently bound through the latter group. The catalytic property of the enzyme was preserved (8% of the specific activity estimated for the soluble enzyme) and all the magnetic amyloglucosidase Dacron derivative was recovered by using a magnetic field. No activity was detected in the supernatant.     

Relating Total π-Electron Energy and Resonance Energy of Benzenoid Molecules with Kekulé- and Clar-Structure-Based Parameters

Within classes of isomeric benzenoid hydrocarbons various Kekulé- and Clar-structure-based parameters (Kekulé structure count, Clar cover count, Herndon number, Zhang–Zhang polynomial) are all mutually correlated. This explains why both the total π-electron energy (E), the Dewar resonance energy (DRE), and the topological resonance energy (TRE) are well correlated with all these parameters. Nevertheless, there exists an optimal value of the variable of the Zhang–Zhang polynomial for which it yields the best results. This optimal value is negative-valued for E, around zero for TRE, and positive-valued for DRE. A somewhat surprising result is that TRE and DRE considerably differ in their dependence on Kekulé- and Clar-structure-based parameters.     

New mono- and bis-carbene samarium complexes: synthesis, X-ray crystal structures and reactivity

New samarium carbene complexes have been synthesized and characterized by X-ray diffraction analysis; the carbenic nature was assessed by reactivity studies.     

Quaternarisation de l'atome d'azote de systemes tautomeres de la serie des oxo-4 thiazoles. Cycloadditions dipolaires 1,3 des thiazoles mesoioniques formes in situ

4-Hydroxythiazoles and N-acylimino 4-thiazolidinones show similar tautomeric behaviour to azlactones. However, the mechanism of their reaction with dimethylacetylenedicarboxylate or with ethyl vinyl ether differs fundamentally. In the thiazole series, the first step is the quaternization of the nitrogen atom. The mesoionic thiazole intermediate is then trapped by a second molecule of the dipolarophile.     

19F NMR chemical shifts of n-F-alkyl compounds

The examination of ¹⁹F chemical shifts for ca. 650 F-alkylated compounds of general formula CF₃(CF₂)_nCF₂X led to the following conclusions: the CF₂ groups α to X are very sensitive to the nature of X, and are spread over a range of 85 ppm. The effect of the length of the F-alkyl chain decreases rapidly, so that δCF₂(α) can already be considered as characteristic of X for n = 1 or 2 for most practical purposes. Solvent effects (in 9 different solvents having ε = 1.8 to 52.1) were found to be rather small except for the F-alkyl iodides. A chart which indicates the domain in which the CF₂(α) resonance signal is to be expected is given for 42 different series of F-alkylated compounds; it is expected to provide the synthetic chemist with a useful tool for the identification and characterization of such compounds.     

Selective Determination of Nanogram γ-Globulin in Human Blood Serum by Resonance Light Scattering of Functionalized Nano-PbS

Functionalized nano-PbS has been prepared and characterized. The functionalized nanoparticles have good dispersibility in water. Reaction of functionalized nano-PbS with γ-globulin (γ-IgG) results an enhanced resonance light scattering (RLS) around 385nm.However, when the content of HSA is lower than 0.5μg/ml^-1 the RLS enhancement is very weak and is nonlinear to concentration of HSA. Based on these results, a new direct quantitative determination method for γ-globulin in blood serum samples without separation is established.Under optimal conditions, the enhanced RLS intensity is in proportion to the γ-IgG concentration in the range 10-500ng/mL. The limit of detection is 2.75ng/mL. This method is proved to be very sensitive, rapid, simple and selective for detection of γ-IgG in blood serum.