Preparation and C NMR study on 1-aryl-3,3-difluoro-2-(phenylethynyl)cyclopropenes: long distance Hammett substituent effect

Coupling of 1-aryl-3,3-difluoro-2-chlorocyclopropenes and phenylacetylene using Sonogashira reaction with Pd(OAc)₂ and CuI as the catalyst with K₂CO₃ as a base yields phenylethynylcyclopropenes in high selectivity and good yields. The ¹³C chemical shifts of C? of ∼105 ppm on acetylene group significantly different from phenylacetylene (84 ppm) suggest that the acetylene group possesses less sp hybrid character due to an unusual long distance Hammett substituent effect. It is also confirmed by the substituent parameter analysis, while the Cβ and C? display the strong resonance effect (their values are 6.89 and 3.37, respectively).     

Characterization of degradation products of poly[(3,3,3-trifluoropropyl)methylsiloxane] by nuclear magnetic resonance spectroscopy, mass spectrometry and gas chromatography

Poly[(3,3,3-trifluoropropyl)methylsiloxane] (PTFPMS) was treated with the solvents acetone, ethyl acetate and methanol and its degradation products were analyzed with multiple techniques. ¹H, ²⁹Si and ¹⁹F nuclear magnetic resonance (NMR) spectroscopy were useful for the characterization of the intact polymers and for the determination of cyclosiloxanes. Cyclosiloxanes with a ring size of up to 23 were quantified by gas chromatography. The only degradation products found were TFPmethyl-cyclosiloxanes. 1,3,5,7-Tetrakis(TFPmethyl)-cyclotetrasiloxane was predominant, and (TFPmethyl)cyclotri-, penta- and hexasiloxane could be detected at lower concentrations. The identity of cyclic degradation products with a ring size of up to 6 was unambiguously confirmed by direct infusion mass spectrometry. The TFPmethyl-cyclosiloxanes were successfully ionized by electrospray ionization in the negative mode. None of the techniques applied gave hints to other degradation products such as short linear oligomers. Almost complete degradation of PTFPMS occurred in acetone and methanol, while degradation is distinctly reduced in ethyl acetate.     

1-Acyl-and 1,2-dihydro-1<Emphasis Type="Italic">H</Emphasis>(acyl)deoxyvasicinones. Synthesis and chemical transformations

1-Acyl-and 1,2-dihydro-1H(methyl, acyl)deoxyvasicinones were synthesized. Their PMR and ¹³C NMR spectra were investigated. The chemical shifts and SSCC were determined. 1-Acyl derivatives were produced by acylation of 1,2-dihydrodeoxyvascinone with caprylyl-and chloroacetylchlorides. It was shown that the Cl atom of 1-chloroacetyldeoxyvasicinone was labile and underwent nucleophilic substitution by amines. In contrast with this, it reacted with cyanide, hydroselenide, methoxide, phenoxide, and anions of compounds with an activated methylene group in a completely different direction to cleave the chloroacetyl group and form 1,2-dihydrodeoxyvasicinone. It was found that addition of 1,2-dihydrodeoxyvasicinone to phenylacetylene occurred regio-and stereoselectively to form the cis-isomer of 1-(2-phenylvinyl)-1,2-dihydrodeoxyvasicinone. __________ Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 353–359, July–August, 2007.     

The Synthesis of Novel Crown Ethers, Part VII [1]. Coumarin Derivatives of Benzocrowns and Cation Binding from Fluorescence Spectra

4-[3-(1-benzopyran-2-one)] derivativesof benzo[12]crown-4, benzo[15]crown-5 andbenzo-[18]crown-6 were synthesized from4-[3-(1-benzopyran-2-one)]-1,2-dihydroxy-benzenereacting with bis-ethyleneglycol dihalides orpentaethylene glycol ditosylate in alkali carbonate/DMF/water. The original products were identified byhigh resolution EI-mass spectra as well as IR,¹H-NMR and ¹³C-NMR spectroscopy. The 1 : 1binding constants of Mg²⁺, Li⁺, Na⁺ andK⁺ with the coumarin-benzocrowns were estimated usingfluorescence emission spectroscopy in acetonitrile.The complexing enhanced quenching fluorescence spectra(CEQFS) and complexing enhanced fluorescence spectra(CEFS) exhibited the ion binding powers due tocationic recognition rules of the macrocycles.     

Novel Synthesis,Characterization of N1,N1,N4,N4-tetrakis (2-hydroxyethyl) terephthalamide (THETA) and Terephthalic Acid (TPA) by Depolymerization of PET Bottle Waste Using Diethanolamine

Chemical depolymerization of poly(ethylene terephthalate) (PET) waste is a possible remedy to huge amount of solid waste generation as it results in degradation products that possess a potential of recyclability. PET bottle waste was depolymerized by aminolysis using diethanolamine. Novel synthesis of N¹, N¹,N⁴,N⁴-tetrakis (2-hydroxyethyl) terephthalamide (THETA) with 73-76% yield and terephthalic acid (TPA) with 78-82% yield was achieved. The purified products were analyzed by FTIR, melting point, DSC, DTG and ¹H-NMR. THETA has various applications in the synthesis of rigid polyurethane foam, unsaturated polyester resins and also as a cross linking agent/ hardener for epoxy resins.     

Cyclotrimerization and linear oligomerization of phenylacetylene on the nickel(I) monocyclopentadienyl complex CpNi(PPh<Subscript>3</Subscript>)<Subscript>2</Subscript>

The reactions of the CpNi(PPh₃)₂ monocyclopentadienyl complex with phenylacetylene and diphenylacetylene in toluene have been studied by ESR. When an alkyne is in twofold molar excess over nickel, it substitutes rapidly for PPh₃ ligands to form the bisalkyne π complex CpNi(η²-C₂PhR)₂, where R = H or Ph. In the case of phenylacetylene, two structural isomers of the Ni(I) π complex have been identified. Irreversible clustering occurs in the system as time passes. When phenylacetylene is in excess, it oligomerizes actively at ambient temperature. The composition of the oligomerization products depends substantially on the reaction temperature: at T = 20°C, the main product is 1,2,4-triphenylbenzene (97% of the conversion products); at T = 40°C, the main products are linear oligomers with an average molecular weight of 1050. The formation and stabilization of active complexes in the system take place when the substrate is in excess. Phenylacetylene trimerization and linear oligomerization schemes in which the Ni(I) monocyclopentadienyl complex stabilized by substrate molecules is the active species are suggested.     

Baseline isotopic data of polyhalogenated compounds

The δ²H- and δ¹³C-values of polyhalogenated compounds were determined by EA-IRMS. Most of the compounds were related to the chloropesticides DDT and its metabolites, hexachlorocyclohexanes, and toxaphene, as well as several polybrominated compounds such as bromophenols and -anisoles. δ²H-values ranged between −235‰ and +75‰ whereas δ¹³C-values were found in the range −22‰ to −38‰. No correlation between δ²H- and δ¹³C-values could be identified. Comparative analysis clarified that bromophenols and the corresponding bromoanisoles may vary in their isotopic distribution. ²H NMR was used to quantify abundances of ²H isotopomers. Quantification of isotopomers of 2,4-dibromophenol and 2,4-dibromoanisole proved that both compounds from different suppliers do not originate from the same source. Differences in the δ²H-values of two toxaphene products were further investigated by the synthesis of products of different degree of chlorination from camphene. It was shown that the δ¹³C-values remained mostly unaltered as was expected since no carbon is lost in this procedure. However, the reaction products became enriched in ²H with increasing degree of chlorination. Different δ²H-values of the starting material will also impact the δ²H-values of the chlorination products.     

Rapid and novel discrimination and quantification of oleanolic and ursolic acids in complex plant extracts using two-dimensional nuclear magnetic resonance spectroscopy—Comparison with HPLC methods

A novel strategy for NMR analysis of mixtures of oleanolic and ursolic acids that occur in natural products is described. These important phytochemicals have similar structure and their discrimination and quantification is rather difficult. We report herein the combined use of proton-carbon heteronuclear single-quantum coherence (¹H-¹³C HSQC) and proton-carbon heteronuclear multiple-bond correlation (¹H-¹³C HMBC) NMR spectroscopy, in the identification and quantitation of oleanolic acid (OA) and ursolic acid (UA)in plant extracts of the Lamiaceae and Oleaceae family. The combination of ¹H-¹³C HSQC and ¹H-¹³C HMBC techniques allows the connection of the proton and carbon-13 spins across the molecular backbone resulting in the identification and, thus, discrimination of oleanolic and ursolic acid without resorting to physicochemical separation of the components. The quantitative results provided by 2D ¹H-¹³C HSQC NMR data were obtained within a short period of time (∼14 min) and are in excellent agreement with those obtained by HPLC, which support the efficiency of the suggested methodology.     

新型吸附剂的合成、表征及其对Ni(II)的吸附研究

利用滴加法合成了球形含Ni^2＋交联壳聚糖, 并通过胺化引入大量活性氨基, 再经除镍制成对重金属镍离子具有较好吸附能力的新型吸附剂[P-C-CTS(Ni)]. 通过Ni^2＋吸附容量的测定, IR及XPS分析, 验证了合成技术路线的正确性. 通过研究pH值对吸附量的影响, 初步讨论了无柠檬酸根(Cit)配位体存在时, 吸附剂对Ni(II)的吸附为螯合作用. 通过Cit存在条件下(c_Ni＝c_Cit＝0.852 mmol•L^－1), 吸附剂对Ni(II)离子和Cit的吸附量随pH值的变化, 结合相应pH值下金属镍的形态分布, 探讨了其对Ni(II)的吸附机理, 研究认为不仅仅是简单的螯合作用, 其吸附机理和吸附量与溶液中金属离子的存在形式有关, 引入静电吸附原理解释了吸附剂对Ni(II)的吸附现象.     

复合催化剂上CO2加氢合成C2烃类

介绍了由CO₂+H₂合成C2⁺烃的几种复合催化剂体系的研究进展，比较和评价了复合催化剂体系的活性和选择性及对C2⁺烃类生成的影响。着重于复合催化剂体系对C4⁺烃的生成及产物分布的影响并简述反应机理。     

Switching the mechanism of polymerisation from vinyl addition to metathesis using single‐site catalysts

Titanium/methylaluminoxane‐based catalyst systems polymerising norbornene by vinyl addition were modified to initiate ring‐opening metathesis polymerisation by interrupting the course of polymerisation with phenylacetylene. The products showed nearly 30% ring‐opened structures according to their ¹H NMR spectra. The change in mechanism of polymerisation after the addition of the reactivity transfer reagent is seen from the kinetic data.     

Diels-Alder reaction of 2-phosphaindolizines catalysed by organoaluminium reagent: theoretical and experimental results

Theoretical calculations at the DFT (B3LYP/6-31+G^**) level of the model Diels-Alder (DA) reactions of 1-methyl-3-(methoxycarbonyl)-2-phosphaindolizine with 1,3-butadiene in the presence of methylaluminium dichloride reveal that the co-ordination of organoaluminium reagent to the carbonyl oxygen increases the activation barrier compared to that for the uncomplexed 2-phosphaindolizine. On the other hand, co-ordination of the organoaluminium reagent to the σ², λ³ P atom lowers the activation barrier by ∼6 kcal mol⁻¹. 1-Methyl-2-phosphaindolizines having an electron-withdrawing group at the 3-position only undergo DA reaction with 2,3-dimethylbutadiene in the presence of the ethylaluminium dichloride catalyst in methylene chloride at a low temperature to afford [2+4] cycloadducts. The formation of an intermediate having the ethylaluminium reagent co-ordinated to σ², λ³ P atom has been detected by ³¹P NMR. The products have been characterized by ³¹P and ¹H NMR studies.     

Tandem regio- and stereospecific cyclization of ethyl isonicotinate with cyanoacetylenic alcohols to provide novel polycondensed heterocyclic systems

Ethyl isonicotinate reacts with tertiary cyanoacetylenic alcohols under exceptionally mild conditions (room temperature, without catalyst or solvent) to afford novel polycondensed heterocyclic systems, 4,15-dioxa-7,12-diazapentacyclo[9.5.2.0^2,10.0^3,7.0^12,16]octadeca-8,17-dienes, in 30-68% yields. This tandem cyclization is regio- and stereospecific. Despite several asymmetric carbons (up to six) being present in the molecules, only one diastereomer is formed and both cyanomethylidene fragments possess exclusively Z-configuration. The tandem sequence includes the formation of 1,3-oxazolidino-1,2-dihydropyridines which undergo Diels-Alder cyclodimerization to give the final products.     

Applications of P NMR spectroscopy in development of M(Duphos)-catalyzed asymmetric synthesis of P-stereogenic phosphines (M = Pt or Pd)

This perspective describes the use of ³¹P NMR spectroscopy in an ongoing research project on enantioselective P−C bond formation catalyzed by platinum and palladium Duphos complexes. This technique was used to characterize catalyst precursors, intermediates and products, to determine equilibrium and rate constants, and to measure the enantiomeric excess (ee) of the P-stereogenic phosphine products. Applications of ³¹P NMR spectroscopy in problem-solving and identifying unexpected products, as well as the analysis of an unusual and esthetically pleasing spectrum, are also discussed.     

Deconvolution of liquid scintillation alpha spectra of mixtures of uranium and radium isotopes

A method for the determination of uranium and radium isotopes in water samples is proposed. Liquid scintillation techniques were used for collecting alpha spectra, which were then analyzed by fitting the alpha peaks with overlapping Gaussians. The analysis can quantify the observed isotopes with accuracy depending on the activity of each isotope.In order to simulate the peaks with Gaussian normal distribution functions, the centroid of each peak as well as the full width at half maximum (FWHM) are required, as they depend on the quenching of the sample. For this purpose, samples with known activities of ²²⁶Ra and its decay products and also of the uranium isotopes ²³⁸U and ²³⁴U, at various quenching levels, were used to establish the correlation of the peaks’ shift with the quench effect. In addition, the correlation of the FWHM with the centroid of a peak was determined, using the same procedure.Following the above analysis technique, an average of 97 ± 2% of detection efficiency and a lower limit of detection of 8.2 mBq kg⁻¹ for alpha isotopes were achieved.     

Dicyanmethylenpyrazolinone und deren Bedeutung als Chromophor. Synthesen mit Nitrilen, 80. Mitt.

1-Phenyl-2-pyrazolin-5-ones1 a–e react with tetracyanoethylene forming the corresponding dicyanomethylenepyrazolin-5-ones2 a–e. The products are deeply coloured with absorption bands between 550 and 650 nm, but low -values and negative solvatochromic effect. By amine-HCN exchange reaction with anilines the red-coloured phenylamino-cyanomethylene-pyrazolinones3–6 are obtained.¹⁵N- and¹³C-NMR-data of2 and quantum-chemical calculations (INDO/S-CI) reveal the extreme polarization and chromophoric properties of the described dicyanomethylene-pyrazolinones.

     

A mass spectrometric method to determine activities of enzymes involved in polyamine catabolism

An analytical method for the determination of three polyamines (putrescine, spermidine, and spermine) and five acetylpolyamines [N¹-acetylspermidine (N¹AcSpd), N⁸-acetylspermidine (N⁸AcSpd), N¹-acetylspermine, N¹,N⁸-diacetylspermidine, and N¹,N¹²-diacetylspermine] involved in the polyamine catabolic pathway has been developed using a hybrid tandem mass spectrometer. Heptafluorobutyryl (HFB) derivatives of these compounds and respective internal standards labeled with stable isotopes were analyzed simultaneously by TOF MS, based on peak areas appearing at appropriate m/z values. The isomers, N¹AcSpd and N⁸AcSpd were determined from their fragment ions, the acetylamidopropyl and acetylamidobutyl groups, respectively, using MS/MS with ¹³C₂-N¹AcSpd and ¹³C₂-N⁸AcSpd which have the ¹³C₂-acetyl group as an internal standard. The TOF MS method was successfully applied to measure the activity of enzymes involved in polyamine catabolic pathways, namely N¹-acetylpolyamine oxidase (APAO), spermine oxidase (SMO), and spermidine/spermine N¹-acetyltransferase (SSAT). The following natural substrates and products labeled with stable isotopes considering the application to biological samples were identified; for APAO, [4,9,12-¹⁵N₃]-N¹-acetylspermine and [1,4,8-¹⁵N₃]spermidine (¹⁵N₃-Spd), respectively; for SMO, [1,4,8,12-¹⁵N₄]spermine and ¹⁵N₃-Spd, respectively; and for SSAT, ¹⁵N₃-Spd and [1,4,8-¹⁵N₃]-N¹-acetylspermidine, respectively.     

Preparation of the novel fluorine-18-labeled VIP analog for PET imaging studies using two different synthesis methods

Vasoactive intestinal peptide (VIP) receptors are expressed on various tumor cells in much higher density than somatostatin receptors, which provides the basis for radiolabeling VIP as tumor diagnostic agent. However, fast proteolytic degradation of VIP in vivo limits its clinical application. With the aim to develop and evaluate new ligands for depicting the VIP receptors with positron emission tomography (PET), the structure modified [R^8,15,21, L¹⁷]-VIP analog was radiolabeled with ¹⁸F using two different methods. With the first method, N-4-[¹⁸F]fluorobenzoyl-[R^8,15,21, L¹⁷]-VIP ([¹⁸F]FB-[R^8,15,21, L¹⁷]-VIP 7) was produced in a decay-corrected radiochemical yield (RCY) of 33.6 ± 3%, a specific radioactivity of 255 GBq/μmol (n = 5) within 100 min in four steps. Similarly, N-4-[¹⁸F](fluoromethyl)-benzoyl-[R^8,15,21, L¹⁷]-VIP ([¹⁸F]FMB-[R^8,15,21, L¹⁷]-VIP 8) was synthesized in a RCY of 34.85 ± 5%, a specific radioactivity of 180 GBq/μmol (n = 5) within 60 min in only one step. The two products 7 and 8 were both shown good stability in HSA. Moreover, the low bone uptakes of 7 and 8 in vivo of mice showed good defluorination stability.     

Reactivity of Aquadiethylenetriamineplatinum(II) Ion with Disulfide Moiety Cystine: A Kinetic and Mechanistic Approach

Abstract

Substitution reactions of the complex [Pt(dien)H₂O]²⁺ (where dien = diethylentriamine or 1,5-diamino-3-azapentane) with sulfur-containing L-cystine have been studied in a 1.0 × 10^?1 mol dm^?3 aqueous perchlorate medium at various temperatures (298–323 K) and 4.45 ≤ pH ≤ 2.15 using UV-vis spectroscopy. The products obtained have been characterized by their infrared and ¹H NMR datasets at various pH levels and temperatures. From infrared and ¹H NMR data, products have indicated that [Pt(dien)H₂O]²⁺ reacted with L-cystine forming a Pt–S bond at low pH. At high pH, a product complex through the Pt–N bond has been formed. All rate constants have been evaluated from nonlinear double exponential plots. The activation parameters ΔH^# and ΔS^# have been determined using the Eyring equation. The products, S_Ni, and reversible rate constants have been evaluated.

Supplemental materials are available for this article. Go to the publisher's online edition of Phosphorus, Sulfur, and Silicon and the Related Elements to view the free supplemental file.

GRAPHICAL ABSTRACT      

Identification Des Produits De La Reduction Electrochimique d'Un Nouvel Antiinflammatoire: Le Piroxicam

Abstract

The electrochemical reduction of piroxicam has been investigated on a mercury pool in acidic and alcaline media.

After exhaustive electrolysis, the extraction followed by chromatographic separation of the reaction products gives the reduced compounds which have been identified by spectroscopic techniques. From the analysis of the NMR ¹H, ¹³C and IR spectra and the results of our preceding electrochemical investigation, the polarographic behaviour of piroxicam has been elucidated. The process occurs by the irreversible reduction of the double bond of the enol function over the total pH range investigated. However, in alkaline and highly acidic solutions, a preceding two-electron step occurs, giving rise to the opening of the thiazine ring.