负载型杂多酸催化下N2O5对甲苯的选择性硝化

用负载型杂多酸为催化剂,N2O5为硝化剂的新型硝化体系,对甲苯的硝化反应进行研究. 分别考察了杂多酸类型、载体种类、杂多酸负载量及催化剂循环使用次数等因素对硝化反应的影响. 结果证明,负载型杂多酸能显著提高N2O5的硝化能力;催化剂回收后可直接重复使用,甲苯硝化反应得率为34%,对位选择性达到58.9%,表明N2O5是一种具有应用前景的硝化试剂.     

单取代芳烃的硝化

以甲苯、乙苯、异丙苯、叔丁基苯、氟苯等为硝化底物,通过混酸硝化得到这些单取代芳烃转化率最大时的混酸硝化强度φ。 运用密度泛涵理论,在B3LYP/6-311G**水平上优化了9种单元芳烃的几何构型,计算苯环上C原子电荷分布。 讨论了9种取代基的定位效应,以苯环取代基以外环上C原子总净电荷QRΣC(2~6)表示单取代苯的硝化反应活性与硝化强度φ之间的关系。 实验结果表明,烷基苯、卤苯、硝基苯的硝化反应活性与其混酸硝化转化率达最大时的混酸硝化强度φ呈良好的线性关系。     

谷胱甘肽和Ebselen对胰岛素硝化的抑制及其相互作用机理的研究

生物体内NO和超氧阴离子快速反应生成的过氧亚硝酸根离子(ONOO^-，peroxynitrite)是一种强细胞毒性物质，它诱导蛋白质酪氨酸残基硝化是其损伤生物系统的重要途径之一。为了探讨谷胱甘肽和ebselen对胰岛素硝化的抑制及其相互作用机理，采用UV-Vis、HPLC和ESI-MS等方法，研究了ONOO^-对胰岛素的硝化作用、小分子抗氧化剂谷胱甘肽(GSH)和ebselen对ONOO^-硝化胰岛素的影响以及它们之间的相互作用。结果表明单独的GSH和ebselen对ONOO^--引发的胰岛素硝化均有明显的抑制，而作为谷胱甘肽过氧化物酶(GPx)的底物GSH 与GPx的模型化合物ebselen之间存在相互拮抗作用，经过对其产物分析，确定其机理是GSH和ebselen能够直接反应生成一种加合物，从而抑制了GSH和ebselen各自的抗硝化能力。     

Zeolite-assisted regioselective synthesis of dinitronaphthalene

The nitration selectivity of naphthalene was studied in different organic solvents with 95 % fuming nitric acid as nitration reagent. The yield of dinitronaphthalene can achieve 78 % in hexane. With nitrogen dioxide as nitration reagent in oxygen, the selectivity of dinitronaphthalene in different types of molecular sieve catalyst was studied. When HBEA zeolite catalyst was used, the yield of dinitronaphthalene was up to 61 %. This method is easy to carry out, environmentally benign, and economical.     

硝基苯的制备及废硫酸回收利用的研究

苯在四氯化碳溶剂中以硝酸和疏酸的混合酸为硝化剂在温和条件下进行硝化，硝基苯的产率高，硫酸可以回收再利用。例如，在带有搅拌器、滴液漏斗、温度计和冷凝器的四颈烧瓶中，加入４４．４毫升苯和４０毫升四氯化碳，将３９．５毫升浓硝酸和４１．５毫升浓硫酸混合后从滴液漏斗中滴加，维持温度在１５～５５℃之间，约４０分钟滴完后，在５５～６２℃继续反应３０分钟。有机层分别用水、１０％氢氧化钠溶液、水洗涤，干燥、蒸馏，先蒸出溶剂可再用。然后收集２０４～２１０．８℃的馏份，得硝基苯６０．６克，产率９８．５３％。废硫酸通过蒸馏浓缩后，可重新用于硝化反应。     

负载型杂多酸催化下N2O5对氯苯的选择性硝化研究

使用负载型杂多酸为催化剂,N2O5为硝化剂的新型硝化体系,对氯苯的硝化反应进行研究。文章分别考察了杂多酸类型、载体种类、杂多酸负载量及催化剂循环使用次数等因素对硝化反应的影响。结果证明,N2O5硝化反应属于酸催化反应,负载型杂多酸能显著提高N2O5的硝化能力;催化剂回收后可直接重复使用,催化活性没有明显的降低。在优化条件下,氯苯硝化反应得率为26%,对位选择性达到68.8%,表明N2O5是一种具有应用前景的硝化试剂,可取代传统的硝硫混酸硝化法,减少废酸处理,符合绿色环保要求。     

Mass spectrometry analysis of in vitro nitration of a recombinant human IgG1 monoclonal antibody

Nitration of a recombinant human monoclonal antibody was carried out in vitro by incubating the antibody with the nitrating reagent tetranitromethane (TNM). The susceptible sites of nitration were identified using high-performance liquid chromatography/mass spectrometry (HPLC/MS). In general, tyrosine residues in the variable domains of the antibody are more susceptible to nitration, while tyrosine residues in the constant domains are relatively resistant to nitration. However, one tyrosine residue in the CH1 domain and one tyrosine residue in the CH2 domain are highly susceptible to nitration. Interestingly, the susceptible tyrosine residue in the CH2 domain is followed by the conserved asparagine residue that is glycosylated.     

NO(2)(+) nitration mechanism of aromatic compounds: electrophilic vs charge-transfer process

The nitration of methylnaphthalenes with NO(2)BF(4) and NOBF(4) was examined in order to shed light on the controversial aromatic nitration mechanism, electrophilic vs charge-transfer process. The NO(2)(+) nitration of 1,8-dimethylnaphthalene showed a drastic regioselectivity change depending on the reaction temperature, where ortho-regioselectivity at -78 degrees C and para-regioselectivity at 0 degrees C were considered to reflect the electrophilic and the direct or alternative charge-transfer process, respectively, because the NO(+) nitration through the same reaction intermediates as in the NO(2)(+) nitration via a charge-transfer process resulted in para-regioselectivity regardless of the reaction temperature. The NO(2)(+) nitration of redox potential methylnaphthalenes higher than 1,8-dimethylnaphthalene gave a similar ortho-regioselectivity enhancement to 1,8-dimethylnaphthalene at lower temperature, thus reflecting the electrophilic process. On the other hand, the NO(2)(+) nitration of redox potential methylnaphthalenes lower than 1,8-dimethylnaphthalene showed para-regioselectivity similar to the NO(+) nitration, indicating the direct or alternative charge-transfer process. In the presence of strong acids where the direct charge-transfer process will be suppressed by protonation, the ortho-regioselectivity enhancement was observed in the NO(2)(+) nitration of 1,8-dimethylnaphthalene, suggesting that the direct charge-transfer process could be the main process to show para-regioselectivity. These experimental results imply that the NO(2)(+) nitration proceeds via not only electrophilic but also direct charge-transfer processes, which has been considered to be unlikely because of the high energy demanding process of a bond coordination change between NO(2)(+) and NO(2). Theoretical studies at the MP2/6-31G(d) level predicted ortho- and para-regioselectivity for the NO(2)(+) nitration via electrophilic and charge-transfer processes, respectively, and the preference of the direct charge-transfer process over the alternative one, which support the experimental conclusion     

Practical neutral aromatic nitration with nitrogen dioxide in the presence of heterogeneous catalysts under moderate oxygen pressure

A practical neutral aromatic nitration process using nitrogen dioxide in the presence of FeCl₃ · 6H₂O under 40–100 psig of oxygen was developed, and nitration of several aromatic compounds, including the deactivated nitrobenzene, was performed in a successful manner. The correlation of reaction rate with equivalents nitrogen dioxide, oxygen pressure, amount of catalyst and temperature was investigated through the nitration of benzene. Following the optimization of reaction conditions, the nitration of benzene was scaled up to 476 mol. Furthermore, inorganic solid catalysts with pore size over 5 Å and surface area over 100 m²/g were applied to newly developed neutral nitration.     

Kinetics and Mechanism of p-Nitrochlorobenzene Nitration with Nitric Acid

Kinetics of homogeneous nitration of p-nitrochlorobenzene with 85-95% nitric acid was investigated. An introduction of a nitro group into a chlorobenzene molecule results in 1600 times deceleration of nitration. It was presumed from comparison of kinetic parameters and correlations of log keff for the mono- and dinitration with the acidity functions of nitric acid that the limiting stage in p-nitrochlorobenzene nitration was the transformation of diffusion pairs into reaction products, whereas in chlorobenzene nitration the limiting stage consisted in diffusion pairs formation.     

Nitration of acetyl derivatives of 1-methylpyrazole

The nitration of acetyl-substituted 1-methylpyrazoles with nitric acid in 20% oleum and in acetic anhydride was studied. Dipyrazoloylfuroxans are formed in the case of nitration in oleum. 4-Nitro-3-acetyl-1-methylpyrazole was obtained by nitration of 3-acetyl-1-methylpyrazole in acetic anhydride.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 833–835, June, 1991.     

Dual selective nitration in Arabidopsis: Almost exclusive nitration of PsbO and PsbP,and highly susceptible nitration of four non‐PSII proteins,including peroxiredoxin II E

Protein tyrosine nitration is a selective process, as revealed in studies of animals. However, evidence for selective protein nitration in plants is scarce. In this study, Arabidopsis plants were exposed to air with or without nitrogen dioxide at 40 ppm for 8 h in light. Proteins extracted from whole leaves or isolated chloroplasts were subjected to 2D PAGE followed by SYPRO Ruby staining and immunoblotting using an anti‐3‐nitrotyrosine antibody. We determined the relative intensity of a spot on an immunoblot (designated RISI), and relative intensity of the corresponding spot on SYPRO Ruby gel (designated RISS). Proteins that exhibited a high RISI value and/or a high RISI/RISS ratio were considered selectively nitrated. In whole leaf proteins from exposed plants, all immunopositive spots were identified as PsbO1, PsbO2 or PsbP1 by PMF. Thus, nitration was exclusive to PsbO and PsbP, extrinsic proteins of photosystem II (PSII). Their RISI/RISS ratio was ≤1.5. Non‐exposed plants showed very faint nitration. In purified chloroplast proteins, PsbO and PsbP accounted for >80% of the total RISI values, while four non‐PSII proteins, including peroxiredoxin II E, exhibited high RISI/RISS ratios (2.5～6.6). Tyr⁹ of PsbO1 was identified as a nitration site. Thus, nitration is selective for two PSII and four non‐PSII proteins in Arabidopsis.     

蒽醌混酸硝化与O3-NO2硝化产物分布的理论研究

运用密度泛函理论方法，研究了混酸和O3－NO2体系两种硝化剂硝化蒽醌的机理和热力学。由于反应机理不同，采用混酸硝化剂时反应的选择性很差，而采用O3－NO2体系硝化剂，反应具有良好的1位选择性和单硝化选择性。     

Radiation-induced nitration of organic compounds in aqueous solutions

Radiation-induced nitration of organic compounds in aqueous solutions was studied. It was found that γ-irradiation of solutions containing acetic and nitric acid and/or their salts gives nitromethane. Dependences of the product yield on the absorbed dose and the contents of components were established. The mechanism of radiation nitration involving radicals is discussed.     

6-氯-2(1 H)-喹喔酮合成方法的改进

设计了以对氯苯胺和氯乙酰氯为原料,经缩合、硝化、还原、环合、氧化五步制得6-氯-2(1H)-喹喔酮的位置选择性合成方法,并对以氯乙酰氯作为苯胺的氨基保护试剂进行硝化的反应和对含活泼氯的硝基化合物进行还原的反应进行了研究.研究结果表明以氯乙酰氯作为苯胺的氨基保护试剂进行硝化的反应符合一般的硝化定位规则,而含活泼氯的硝基化合物的还原在优化条件下以铁粉为还原剂可以高选择性获得目标产物.     

Urea Nitrate : A Reagent for Regioselective Nitration of Aromatic Amines

Nitration o f the aromatic amines with urea nitrate in sulphuric acid gave exclusively the p-isomer and when the p-position is blocked, the nitration occurred to give a m-nitroaniline derivative in excellent yields. However, nitration was not effected at o-position. Mechanistic aspect of this reaction is also discussed.     

Selective scavenging property of the indole moiety for the nitrating species of peroxynitrite

The inhibitory effect on tyrosine nitration and oxidation of peroxynitrite was evaluated for more than 40 reagents including natural and synthetic compounds, and the inhibiting efficiency of each compound for nitration was compared with that for oxidation, to characterize its property as a peroxynitrite scavenger. In the presence of various concentrations of testing compounds, the nitrating and oxidizing activities were measured by monitoring the formation of 3-nitrotyrosine and dityrosine with an HPLC-UV-fluorescence detector. The IC(50) values for nitration and oxidation were determined, and the ratio of these two IC(50) values was calculated for each compound. Although the IC(50) values varied from compound to compound, it was revealed that the ratio of two IC(50) values (IC(50) for oxidation/IC(50) for nitration) was 1 in almost all the compounds tested, except five indole derivatives (L-tryptophan, melatonin, 5-methoxytryptamine, tryptamine, and tetrahydro-beta-carboline) and one synthetic selenium-containing compound ((2R,3R,4S)-2-amino-3,4-dihydroxy-5-phenylselenopentan-1-ol, ADPP). The indole derivatives showed a specific inhibitory effect on tyrosine nitration without affecting the oxidation. ADPP was confirmed to have a preferable inhibitory activity for tyrosine oxidation. It was suggested that compounds showing an IC(50) value ratio of 1 scavenged the common species for nitration and oxidation, while the indole derivatives and ADPP preferably scavenged the nitrating and oxidizing species, respectively. From a stopped flow study, it was also revealed that the nitrotyrosine formation was relatively slow, unlike an OH radical reaction. These results imply that the peroxynirite reaction at least partly proceeds through specific species for nitration.     

Product analyses of ozone mediated nitration of benzimidazole derivatives with nitrogen dioxide: formation of 1-nitrobenzimidazoles and conversion to benzotriazoles

Several benzimidazole derivatives having electron-withdrawing or -donating substituent(s) at the benzene moiety were used as models of the imidazole moiety of purine bases and their nitration with nitrogen dioxide and ozone (so-called Kyodai nitration) were examined. Products were extracted from the reaction mixture with AcOEt and their structures were analyzed. 1-Nitrobenzimidazole derivatives and unexpected 1-nitrobenzotriazole derivatives were identified. Although the yields of 1-nitrobenzimidazole derivatives were quite low, these were all new compounds that could be obtained only by Kyodai nitration. It was speculated that benzotriazoles were formed via 1-nitrobenzimidazoles and subsequent nitration toward benzotriazoles resulted in the formation of 1-nitrobenzotriazoles.     

水相中取代苯酚的硫酸氢钠/硝酸钠硝化反应

以硫酸氢钠和硝酸钠为硝化剂,在水溶液中完成了取代苯酚的硝化反应.硝化产物具有良好的选择性和较高的产率.     

Equilibrium constants of cellulose nitration by nitric acid under quasi-homogeneous conditions

The equilibrium of nitration of cellulose was studied at 13.1 and 20 °C in aqueous solutions of HNO₃ (77.3–80.5 wt.%) forming quasi-homogeneous solutions with cellulose. At 20 °C under quasi-homogeneous conditions, the rates of cellulose nitration are comparable to those of homogeneous nitration of alcohols. The effective nitration constants differ substantially for heterogeneous and homogeneous reactions. Using IR spectra, the partial conversions in the nitration to the 2, 3 and 6 positions of the glucopyranose cycle and the effective equilibrium constants of formation of different isomeric nitrates were estimated. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 1, pp. 66–70, January, 1999.