The reaction of the bis(ethylene) complex [Tp(Me(2) )Ir(C(2)H(4))(2)] (1) (Tp(Me(2) ): hydrotris(3,5-dimethylpyrazolyl)borate) with two equivalents of dimethyl acetylenedicarboxylate (DMAD) in CH(2)Cl(2) at 25 degrees C gives the hydride-alkenyl species [Tp(Me(2) )IrH{C(R)=C(R)C(R)=C(R)CH=CH(2)}] (2, R: CO(2)Me) in high yield. A careful study of this system has established the active role of a number of intermediates en route to producing 2. The first of these is the iridium(I) complex [Tp(Me(2) )Ir(C(2)H(4))(DMAD)] (4) formed by substitution of one of the ethylene ligands in 1 by a molecule of DMAD. Complex 4 reacts further with another equivalent of the alkyne to give the unsaturated metallacyclopentadiene [Tp(Me(2) )Ir{C(R)=C(R)C(R)=C(R)}], which can be trapped by added water to give adduct 7, or can react with the C(2)H(4) present in solution generating complex 2. This last step has been shown to proceed by insertion of ethylene into one of the Ir--C bonds of the metallacyclopentadiene and subsequent beta-H elimination. Complex 1 reacts sequentially with one equivalent of DMAD and one equivalent of methyl propiolate (MP) in the presence of water, with regioselective formation of the nonsymmetric iridacyclopentadiene [Tp(Me(2) )Ir{C(R)=C(R)C(H)=C(R)}(H(2)O)] (9). Complex 9 reacts with ethylene giving a hydride-alkenyl complex 10, related to 2, in which the C(2)H(4) has inserted regiospecifically into the Ir--C(R) bond that bears the CH functionality. Heating solutions of either 2 or 10 in CH(2)Cl(2) allows the formation of the allyl species 3 or 11, respectively, by simple stereoselective migration of the hydride ligand to the Calpha alkenyl carbon atom and concomitant bond reorganization of the resulting organic chain. All the compounds described herein have been characterized by microanalysis, IR and NMR spectroscopy, and for the case of 3, 7, 7CO, 8NCMe, 9, 9NCMe, and 10, also by single-crystal X-ray diffraction studies. 相似文献
Sulfasalazine is an antibiotic used in the treatment of inflammatory bowel diseases. For the assessment of sulfasalazine in several biological matrices, an Enzyme-Linked Immunosorbent Assay (ELISA) method based on polyclonal antibodies was developed and characterized.The immunoassay showed a high sensitivity (IC50 = 0.51 ng mL−1) and specificity, a detection limit of 0.02 ng mL−1 and a dynamic range of 0.06-3.75 ng mL−1 (80-20% inhibition). The immunoassay performed well when it was applied to spiked plasma samples (from 0.5 to 2.0 ng mL−1) previously cleaned up by protein precipitation with methanol. Recoveries ranged from 83 to 119%, with a mean value of 99% (CV = 13%).Since sulfasalazine remaining of a treatment reaches the systemic circulation in unchanged form, the immunoassay can be applied to the determination of this pharmaceutical in human plasma in order to facilitate the control of the patients through the application of personal doses. 相似文献
This study presents a simple method for measuring long-range heteronuclear coupling constants between protons and proton-bearing carbons. The approach involves recording two conventional 1D-TOCSY experiments in which the offset of the selective proton pulse is set on the low- and high-frequency 13C satellites of an isolated proton signal, Hi. Long-range heteronuclear coupling values between the 13Ci bonded to Hi and the protons Hj,k...n that belong to the same spin system were easily determined from the relative displacement of the relayed Hj,k...n signals in the satellite-selective TOCSY spectra. The sense of the displacement indicated the sign of the coupling constants. 相似文献
Conjugate addition reactions of various types of nucleophiles to the γ-lactam unit of dihydroindolizinone systems have been studied. The addition of cuprates, amines or stabilized carbanions requires the activation of the unsaturated bicyclic lactam with a EWG at C-2, while sulfur-stabilized carbanions are reactive enough to add to the unsubstituted lactam. The stereochemical outcome of the conjugate addition reaction depends on the nature of the substituent at the angular position, and the incoming nucleophile. Thus 1,10b-cis or 1,10b-trans diastereomers could be obtained selectively with dr>95:5. The tandem conjugate addition–alkylation also takes place in good yields. These reactions have been applied to the synthesis of enantiopure tetrahydropyrrolo[2,1-a]isoquinolines. 相似文献
The state of the art of immunoanalysis for the determination of tetracycline and sulfonamide residues in food products is
reviewed. Special attention is paid to the design and synthesis of haptens, providing an overview of the efforts spent on
developing antibiotic screening methods to determine residue levels in agreement with the legislation. The results and observations
published, focused on tetracycline and sulfonamide enzyme-linked immunosorbent assays, are discussed. 相似文献
A new mixed-ligand nickel(II) coordination compound [Ni(bz)2(phen)2] (1) (bz = benzilate and phen = 1,10-phenanthroline) has been synthesized by refluxing nickel(II) acetate with benzilic acid
and 1,10-phenantholine. Compound 1 has been characterized by elemental analysis, IR and electronic absorption spectroscopy, magnetic measurements, thermogravimetric
analysis and single-crystal X-ray diffraction The crystal of 1 belongs to monoclinic crystal system, space group C2/c and its unit cell parameters are a = 25.881(3), b = 11.1728(15), c = 17.609(2) ? and β = 124.104(3)°. The effect of non-covalent interactions, such as π···π and C–H···π, on the 3D supramolecular
organization of this molecular complex is analyzed. 相似文献
The crystal structure together with unambiguous assignation of 1H and 13C NMR signals of 3-epismilagenin acetate 4 and 23-oxo-3-epismilagenin acetate 5 are described. Compound 4, crystallized as orthorhombic system a = 10.535(1) ?, b = 13.775 (1) ?, c = 18.347 (1) ?, α = β = γ = 90°; with space group P212121; while compound 5 crystallized as a monoclinic system a = 10.380(1) ?, b = 7.327(1) ?, c = 17.881(1) ?, α = γ = 90°, β = 99.56(1)°, with a space group P21. The presence a carbonyl group at C(23) in compound 5 produces a significant deviation from the chair conformation observed in compound 4. The effects of the side chain modifications on the puckering parameters derived from are discussed. 相似文献
Conjugate addition reactions of sulfur-stabilized nucleophiles to the delta-lactam unit of tetrahydrobenzo[a]benzoquinolizines have been studied. The stereochemical outcome of the conjugate addition reaction depends on the nature of the substituent at the angular position, thus 2,11b-cis or 2,11b-trans diastereomers could be obtained selectively. The tandem conjugate addition-alkylation also takes place in good yields and with high diastereoselectivity. The polyfunctionalized hexahydrobenzo[a]quinolizinone systems obtained could be further elaborated toward emetine-like structures. 相似文献
A new class of compounds, mono- and bis-haloethylphosphonates (HAPs and bisHAPs, respectively), listed in Schedule 2.B.04 of the Chemical Weapons Convention (CWC), has been synthesized and studied by GC-MS with two aims. First, to improve the identification of this type of chemicals by the Organization for the Prohibition of Chemical Weapons, (OPCW). Second, to study the synergistic effect of halogen and silicon atoms in molecules undergoing mass spectrometry. Fragmentation patterns of trimethylsilyl derivatives of HAPs were found to depend on the nature of the halogen atom; this was in agreement with DFT-calculations. The data suggest that a novel intramolecular halogen transfer takes place during the fragmentation process.
