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Xiaogong Wang - One of the best experts on this subject based on the ideXlab platform.
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synthesis of side on liquid crystalline diblock copolymers through macromolecular Azo Coupling reaction
European Polymer Journal, 2015Co-Authors: Renbo Wei, Xiaogong WangAbstract:Abstract We report a strategy for the synthesis of side-on liquid crystalline diblock copolymers by a combination of atom transfer radical polymerization (ATRP) method and a macromolecular Azo Coupling reaction. The liquid crystalline block, with a terminus suitable for Azo Coupling reaction, was obtained by ATRP using a synthesized ATRP initiator with the designed functional group and a side-on liquid crystalline monomer. The other block, with a diAzonium salt terminus, was obtained by the diAzotization of aniline-functionalized PEG. The macromolecular Azo Coupling reactions between above two polymer blocks were carried out in DMF. The products and intermediates were characterized by GPC, 1H NMR, FT-IR, POM and DSC.
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synthesis of y shaped amphiphilic copolymers by macromolecular Azo Coupling reaction
RSC Advances, 2015Co-Authors: Jilei Wang, Yuqi Zhou, Xiaogong WangAbstract:The synthesis of AB2 Y-shaped amphiphilic block copolymers by macromolecular Azo Coupling reaction is reported. The hydrophobic block with the functional group at the end of the polymeric chain was prepared by controlled radical polymerization methods such as RAFT and ATRP. The hydrophilic block with diAzonium salt group was obtained by the diAzotization of V-shaped aniline-functionalized PEG. Then Y-shaped block copolymers were easily prepared through macromolecular Azo Coupling reactions between the abovementioned two polymeric blocks. The results of experiments showed that the position of the functional group suitable for Azo Coupling reaction in the polymeric chain has considerable effect on the efficiency of macromolecular Azo Coupling reaction. It was easier for the macromolecular diAzonium salts to attack the functional groups when they were at the end of the macromolecular chains instead of in the middle. The self-assembly properties of the obtained Y-shaped amphiphilic block copolymers were also studied. Colloidal spheres were prepared by gradual hydrophobic aggregation of the polymeric chains in a THF–H2O dispersion medium.
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synthesis of block copolymers via the combination of raft and a macromolecular Azo Coupling reaction
Polymer Chemistry, 2013Co-Authors: Dan Liu, Renbo Wei, Xiaogong WangAbstract:We report a novel modular strategy for the synthesis of block copolymers via the combination of a macromolecular Azo Coupling reaction and a reversible addition fragmentation chain transfer (RAFT) polymerization method. One block, with a terminus suitable for an Azo Coupling reaction, was obtained by RAFT polymerization using a synthesized chain transfer agent (CTA) with the designed functional group. The other block, with a diAzonium salt terminus, was obtained by the diAzotization of aniline-functionalized PEG, which was prepared by a nucleophilic substitution reaction between the synthesized tosylate ended mPEG and p-aminobenzoic acid. The macromolecular Azo Coupling reaction between the above two polymer blocks was carried out in a polar organic solvent such as DMF under extremely mild conditions. Block copolymers with well-defined structures can be efficiently prepared through this approach.
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synthesizing amphiphilic block copolymers through macromolecular Azo Coupling reaction
Chemical Communications, 2012Co-Authors: Renbo Wei, Zhen Chen, Xiaogong WangAbstract:This communication reports a new approach to synthesize amphiphilic block copolymers. The copolymers with well-defined structures were synthesized by macromolecular Azo-Coupling reaction between the diAzonium salt of aniline-functionalized PEG and the polymeric blocks with a terminal suitable for the Azo-Coupling reaction.
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hyperbranched Azo polymers synthesized by Azo Coupling reaction of an ab2 monomer and postpolymerization modification
Macromolecules, 2005Co-Authors: Pengchao Che, Xiaogong WangAbstract:A series of hyperbranched Azo-polymers have been synthesized by two-stage Azo-Coupling reactions, in which a hyperbranched precursor Azo-polymer (HPAP) was prepared by step-growth polymerization of an AB2 monomer through Azo-Coupling reaction and then was further modified by postpolymerization Azo-Coupling reaction at the peripheral groups. The AB2 monomer, di[2-(N-ethylanilino)ethyl]-5-aminoisophthalate, was synthesized from the nucleophilic substitution reaction between N-ethyl-N-(2-chloroethyl)aniline and 3,5-bis(carboxyl)aniline. On the basis of the monomer, HPAP was prepared by step-growth polycondensation of the diAzonium salt of the AB2 monomer. The hyperbranched precursor polymer was then reacted with diAzonium salts of 4-nitroaniline, 4-aminobenzoic acid, and 4-aminobenzonitrile to introduce different types of donor−acceptor Azo-chromophores at the peripheral positions. The structure and properties of the Azo-polymers were characterized by the spectroscopic methods and thermal analysis. The hyper...
Vladimír Macháček - One of the best experts on this subject based on the ideXlab platform.
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diAzonium exchange and migration of pivaloyl group upon Azo Coupling of β enaminones
European Journal of Organic Chemistry, 2013Co-Authors: Petr Simůnek, Valerio Bertolasi, Vladimír MacháčekAbstract:4,4-Dimethyl-1-methylamino-1-phenyl-2-(substituted phenyldiazenyl)pent-1-en-3-ones (prepared upon Azo Coupling of 4,4-dimethyl-1-methylamino-1-phenylpent-1-en-3-one 6a with the corresponding benzenediAzonium tetrafluoroborates) react with another molecule of substituted benzenediAzonium tetrafluoroborate (in dichloromethane in the presence of anhydrous sodium acetate) to form substituted 4,4-bis(substituted phenyldiazenyl) derivatives 8. The second Azo Coupling is reversible. Derivatives 8 undergo either reverse cleavage of a diAzonium ion or [1,3] sigmatropic rearrangement forming substituted formazane 9. In the case of the sequential use of two different diAzonium tetrafluoroborates, the less electrophilic group splits off more easily. The structures of the products 9 were studied by means of X-ray, 1H, 13C, 19F and 15N NMR and MALDI HRMS analyses. The formazans 9 exhibit a reduced mobility of the phenyl group adjacent to the pivaloyl group, giving rise to anisochronism of proton and carbon atoms, to eventually form conformers. The reduced mobility was observed by means of NMR spectroscopy. A temperature dependence of the spectral behaviour was also studied.
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stable triazenes derived from 2 alkylaminonaphthalenes and 5 nitrobenzo c 1 2 thiAzole 3 diAzonium hydrogensulfate
European Journal of Organic Chemistry, 2008Co-Authors: Josef Přikryl, Vladimír Macháček, Marketa Svobodova, Petr Jansa, Ales Růžicka, Petr Nachtigall, Michal CernýAbstract:A calculation using the DFT method confirmed that the extraordinary stability of the triazenes formed by an Azo Coupling reaction of 5-nitrobenzo[c]-1,2-thiAzole-3-diAzonium with primary or secondary aromatic amines is caused by the fact that these substances are protonated at the heterocyclic nitrogen atom and not at the nitrogen atom of the triazene grouping –N=N–N(R)Ar. Stable triazenes are also formed by reaction of 5-nitrobenzo[c]-1,2-thiAzole-3-diAzonium with 2-alkylaminonaphthalenes. In the cases of the Azo Coupling reaction with 2-methylamino- and 2-ethylaminonaphthalene, the content of triazenes is almost 50 % in the product mixture with the isomeric Azo compounds. The structures of the triazenes were confirmed by X-ray analysis.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)
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structure and tautomerism of Azo Coupling products from n alkylenaminones derived from acetylacetone and benzoylacetone in solid phase and in solution
New Journal of Chemistry, 2007Co-Authors: Petr Simůnek, Valerio Bertolasi, Marketa Svobodova, Loretta Pretto, Antonin Lycka, Vladimír MacháčekAbstract:A series of Azo Coupling products have been prepared by reaction of substituted benzenediAzonium tetrafluoroborates with N-alkyl 4-aminopent-3-en-2-ones or 3-amino-1-phenylbut-2-en-1-ones. The structure and tautomerism of the reaction products were studied by means of single-crystal X-ray study and by NMR spectroscopy in deuteriochloroform solution. The Azo Coupling products obtained from 4-methylaminopent-3-en-2-ones (3a–i) exist in CDCl3 solution as E/Z isomer mixtures with the Z isomer strongly predominating. The major isomer is a mixture of enamino–Azo and imino–hydrAzo tautomers with the former predominating. The proportion of the Azo form depends on substitution of the benzene ring of the diAzonium salt and decreases in the order of MeO > Me > Br > NO2. The position of tautomeric equilibrium is practically unaffected by switching from 4-methylaminopent-3-en-2-ones to 3-methylamino-1-phenylbut-2-en-1-ones. In the solid phase, the Azo form always predominates; substitution of diAzonium salt and at N3 nitrogen does not significantly affect the position of the tautomeric equilibrium. The Azo Coupling products always exist in the form of a single Z isomer. All determined structures, in the solid state, consist of a mixture of the two tautomeric forms, amino–diazenyl and imino–hydrAzone, in ratios ranging from 82/18 to 91/9%. The weighed superimposition of both the hydrogen-bonded N1N2–C1C2–N3H/ HN1–N2C1–C2N3 heterodienic fragments, however, do not allow to clarify the effects of the para-substituents at the N1-phenyl ring both on the N1⋯N3 hydrogen-bond distances and on the bond lengths in the heterodienic systems within the series 3a–c,f and 4a–c,e,f.
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structure of Azo Coupling products of 5 nitro 2 1 benzisothiAzole 3 diAzonium hydrogensulphate with aromatic amines
Dyes and Pigments, 2007Co-Authors: Josef Přikryl, Vladimír Macháček, Michal Cerný, Hana Bělohlavova, Antonin LyckaAbstract:Abstract The reaction of 5-nitro-2,1-benzisothiAzole-3-diAzonium hydrogensulphate with anilines, N-alkylanilines and diphenylamine gives N-substituted 3-(4-aminophenyldiazenyl)-5-nitro-2,1-benzisothiAzoles 2 and isomeric 1-(5-nitro-2,1-benzisothiAzol-3-yl)-3-substituted-3-phenyltriazenes 1. The predominant reaction products are triazenes 1, being present up to 95% in reaction products. A larger amount of Azo compounds 2 are formed in the reaction of 5-nitro-2,1-benzisothiAzole-3-diAzonium with diphenylamine (about 45%), with N-alkyl-3-methylanilines and 3-methylaniline (as much as 50%). The triazenes formed are extraordinarily stable in acid medium (the decomposition half-lives in 0.5 mol l−1 H2SO4 in aqueous acetic acid (1:1 v/v) are in the order of hours), which is explained by a different site of their protonation: while 1,3-diaryltriazenes are protonated at the –NH–N N– group, triazenes 1 are protonated at the heterocyclic nitrogen. The triazenes 1 formed by Azo Coupling reaction with anilines containing primary amino group undergo an acid–base reaction in methanolic solutions, connected with distinct change in colour, which indicates a considerable acidity of the proton in –NH–N N– grouping.
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formation of pyridazinium salts by Azo Coupling of n substituted 3 amino 1 phenylbut 2 en 1 ones and diAzonium salts
European Journal of Organic Chemistry, 2004Co-Authors: Petr Simůnek, Valerio Bertolasi, Antonin Lycka, Marketa Peskova, Vladimír MacháčekAbstract:Treatment of 3-(2,4-dimethoxyphenylamino)- and 3-methylamino-1-phenylbut-2-en-1-ones with some benzenediAzonium tetrafluoroborates gives, besides the usual Azo Coupling products [i.e., 3-(substituted imino)-1-phenylbutane-1,2-diones 2-(4-substituted phenylhydrAzones) and 2-(4-methoxyphenyldiazenyl)-3-methylamino-1-phenylbut-2-en-1-one, respectively], the previously unreported 1,4,5,6-tetrasubstituted pyridazinium tetrafluoroborates. The pyridazinium salts have been identified by X-ray analysis and by their 1H, 13C, 15N, 11B and 19F NMR spectra. Their formation is most probably the result of nucleophilic attack on the carbonyl carbon by the nitrogen of the hydrAzone group and subsequent dehydration. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Julia R. Shakirova - One of the best experts on this subject based on the ideXlab platform.
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synthesis and intramolecular Azo Coupling of 4 diAzopyrrole 2 carboxylates selective approach to benzo and hetero c fused 6h pyrrolo 3 4 c pyridazine 5 carboxylates
Journal of Organic Chemistry, 2016Co-Authors: Ekaterina E. Galenko, Alexey V. Galenko, Alexander F. Khlebnikov, Mikhail S. Novikov, Julia R. ShakirovaAbstract:A high yield synthesis of fluorescent benzo, thieno, and furo [c]-fused methyl 7-aryl-6H-pyrrolo[3,4-c]pyridazine-5-carboxylates, including unprecedented heterocyclic skeletons, was performed by the transformation of methyl 4-aminopyrrole-2-carboxylate into the corresponding diAzo compound, followed by intramolecular Azo Coupling under acid conditions onto a nucleophilic aryl or hetaryl group in the 3-position. Azo Coupling is completely regioselective and, according to DFT calculations, a kinetically controlled reaction. N-Methylation of 1,3-disubstituted 2H-pyrrolo[3,4-c]cinnolines occurs selectively at N5 under kinetic control, leading exclusively to 5-methyl-5H-pyrrolo[3,4-c]cinnoline derivatives.
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Synthesis and Intramolecular Azo Coupling of 4‑DiAzopyrrole-2-carboxylates: Selective Approach to Benzo and Hetero [c]‑Fused 6H‑Pyrrolo[3,4‑c]pyridazine-5-carboxylates
2016Co-Authors: Ekaterina E. Galenko, Alexey V. Galenko, Alexander F. Khlebnikov, Mikhail S. Novikov, Julia R. ShakirovaAbstract:A high yield synthesis of fluorescent benzo, thieno, and furo [c]-fused methyl 7-aryl-6H-pyrrolo[3,4-c]pyridazine-5-carboxylates, including unprecedented heterocyclic skeletons, was performed by the transformation of methyl 4-aminopyrrole-2-carboxylate into the corresponding diAzo compound, followed by intramolecular Azo Coupling under acid conditions onto a nucleophilic aryl or hetaryl group in the 3-position. Azo Coupling is completely regioselective and, according to DFT calculations, a kinetically controlled reaction. N-Methylation of 1,3-disubstituted 2H-pyrrolo[3,4-c]cinnolines occurs selectively at N5 under kinetic control, leading exclusively to 5-methyl-5H-pyrrolo[3,4-c]cinnoline derivatives
Wim Dehaen - One of the best experts on this subject based on the ideXlab platform.
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ring degenerate rearrangement resulting from the Azo Coupling reaction of a 3 aryl 1 3a 6a triazapentalene
Journal of Organic Chemistry, 2020Co-Authors: Yingchun Wang, Tomas Opsomer, Luc Van Meervelt, Wim DehaenAbstract:The 3-(4-(methoxycarbonyl)phenyl)triazapentalene is a highly fluorescent small molecule which is readily accessible via a two-step synthesis. In the search for postfunctionalization methods, a radical CH-arylation with diAzonium salts was attempted. However, Azo Coupling resulted in a ring-degenerate rearrangement toward a 2-aryl-4-Azotriazapentalene, which was confirmed via crystallographic analysis. A mechanism involving the generation of a nitrilimine is proposed. In addition, reduction of the Azo group led to cleavage of the triazapentalene core. The present results further demonstrate the sensitivity of the triazapentalene fluorophore.
Elisabetta Bertol - One of the best experts on this subject based on the ideXlab platform.
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hair testing of propofol by liquid chromatography tandem mass spectrometry and Azo Coupling derivatization
Drug Testing and Analysis, 2017Co-Authors: Fabio Vaiano, Francesco Mari, Francesco Paolo Busardo, Jennifer P Pascali, Alessia Fioravanti, Claudia Mortali, Elisabetta BertolAbstract:Propofol is a short-acting intravenous hypnotic-amnesiac agent used in the general anesthesia. In recent years propofol has gained importance for recreational use (being able to give euphoria, relaxation, sexual hallucinations and disinhibition) and for suicidal purposes. For these reasons, forensic toxicology interest in this substance has increased as well, taking into account the chance of its detection in hair. In this study, a new method in liquid chromatography-tandem mass spectrometry for hair detection of propofol was applied in two real cases for clinical and forensic purposes. This method consists in propofol derivatization with a diAzonium salt from aniline and a liquid-liquid extraction with dichloromethane and ethyl acetate. Lower limit of quantification in negative ionization mode is 0.1 pg/mg. In Case 1, a segmental analysis was carried out on a sample collected from a female declaring self-administration. Propofol was found in the second and third segment at concentration of 0.21 and 0.11 ng/mg. In case 2, propofol was detected at 0.50 ng/mg in pubic hair from a male underwent a gastroscopy. In this study we validated and successfully applied a new versatile, sensitive and efficient method for hair detection of propofol even after a single administration.
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enhancing the sensitivity of the lc ms ms detection of propofol in urine and blood by Azo Coupling derivatization
Analytical and Bioanalytical Chemistry, 2014Co-Authors: Fabio Vaiano, Francesco Mari, Francesco Paolo Busardo, Elisabetta BertolAbstract:Propofol is a low-polarity, volatile molecule that is difficult for an electrospray ion source (ESI) to ionize in either negative ion mode (NIM) or positive ion mode (PIM), which hampers its detection via liquid chromatography–mass spectrometry. The aim of the present study was to use a new derivatization agent to improve ionization efficiency and to develop an efficient liquid chromatography–multiple mass spectrometry (LC-MS/MS) determination of propofol in urine and blood, taking advantage of an electrophilic aromatic substitution. An Azo-Coupling reaction with a diAzonium salt from aniline was performed to introduce a protonation site into the molecule. The diAzonium salt was generated by aniline in water solution by HCl and sodium nitrite; derivatization was achieved by stirring a mixture of the diAzonium salt and propofol in sodium hydroxide solution for 30 min below 5 °C. A liquid-liquid extraction with dichloromethane and ethyl acetate was performed to obtain the Azo derivative (molecular composition: C18H22ON2; molecular weight: 282 Da) in high yield. The compound provided very high ionization yields in both PIM and NIM ESI, and the protonated or deprotonated molecule gave intense signals. The transitions m/z 283 → 77, 241 and m/z 281 → 176, 161 were chosen for the PIM and NIM, respectively, in order to develop quantitative methods of detecting propofol in urine and blood via triple-quadrupole LC-MS/MS. These methods proved to be highly sensitive, with limits of quantification of 0.4 pg/mL and 0.1 ng/mL obtained in the NIM when analyzing 1 mL of urine and 100 μL of blood, respectively.
