细胞色素P-450模拟体系的活性中间体—亚碘酰苯铬(Ⅳ)四苯基卟啉配合物的分离、表征和氧化反应

铬(Ⅲ)四苯基卟啉-亚碘酰苯体系在温和条件下能催化氧化碳氢化合物,是细胞色素P-450很好的模拟体系。分离和表征细胞色素P-450模拟体系的活性中间体,不仅能解释细胞色素P-450模拟体系催化氧化碳氢化合物的反应机理,而且也有助于深入了解细胞色素P-450催化氧化碳氢化合物的反应机理及其活性中间体的结构。我们首先分离和表征的细胞色素P-450模拟体系的一种活性中间体-氧配位铬(V)四苯基卟啉配合物,具有氧化碳氢化合物的活性。这篇论文报道细胞色素P-450模拟体系的另一种活性中间体-亚碘酰苯铬(Ⅳ)四苯基卟啉配合物的分离,表征和对环已烯的氧化性质。     

细胞色素P-450模拟体系的活性中间体—亚碘酰苯铬(Ⅳ)四苯基卟啉配合物的分离、表征和氧化反应

铬(Ⅲ)四苯基卟啉-亚碘酰苯体系在温和条件下能催化氧化碳氢化合物,是细胞色素P-450很好的模拟体系。分离和表征细胞色素P-450模拟体系的活性中间体,不仅能解释细胞色素P-450模拟体系催化氧化碳氢化合物的反应机理,而且也有助于深入了解细胞色素P-450催化氧化碳氢化合物的反应机理及其活性中间体的结构。我们首先分离和表征的细胞色素P-450模拟体系的一种活性中间体-氧配位铬(V)四苯基卟啉配合物^[1],具有氧化碳氢化合物的活性。这篇论文报道细胞色素P-450模拟体系的另一种活性中间体-亚碘酰苯铬(Ⅳ)四苯基卟啉配合物的分离,表征和对环已烯的氧化性质。     

氧化碘苯对甲苯酚锰(Ⅳ)四苯基卟啉络合物的合成

锰卟啉络合物在温和条件下活化分子氧,选择性地催化氧化碳氢化合物,是单加氧酶细胞色素p-450的很好的模型体系。由于已合成的高价锰卟啉络合物很少,所以严重地阻碍其反应机理和活性中间体的研究。Hill等人合成了二种类型的双核的锰(IV)四     

氧化碘苯间氨基苯甲酸锰(Ⅳ)四苯基卟啉配合物的合成

近年来,化学家们对高价锰卟啉配合物的合成非常感兴趣。高价锰卟啉配合物在温和条件下分解水,释放氧,是植物光体系Ⅱ的可能的模型化合物。锰卟啉配合物在比较温和条件下活化分子氧,选择性地催化氧化碳氢化合物,是单加氧酶细胞色素P-450的很好的模型体系。由于缺少已合成的高价锰卟啉配合物,所以植物光体系Ⅱ和细胞色素P-450模型体系的活性中间体的研究遇到了障碍。Hill等在氯苯中用氧化碘苯氧化XMn(Ⅲ)TPP(TPP=四苯基卟啉基),合成了两类双核的四价锰四苯基卟啉配合物,[XMnⅣ)TPP]_2O(X=N_3~-或OCN~-)和[XMn(Ⅳ)TPP(OIPh)]_2O(X=Cl~-或Br~-,OIPh=氧化碘苯)。但还未能合成出单核的氧化碘苯锰(Ⅳ)四苯基卟啉配合物。我们选择位阻大于Cl~-、Br~-、N_3~-和OCN~-,键合能力介于Cl~-、Br~-与N_3~-、OCN~-之间的间氨基苯甲酸作为轴向配体,成功地合成了单核的m-H_2NC_6H_4CO_2Mn(Ⅳ)TPP(OIPh)(1),并讨论了它的光谱性质。     

迭氮基吡啶四苯基卟啉合铬（Ⅲ）的合成及晶体和分子结构

细胞色素P-450在生物体内温和条件下活化分子氧,选择地催化氧化很不活泼的碳氢化合物。铬(Ⅲ)卟啉配合物在温和条件下以亚碘酰苯或过氧羧酸等为氧化剂可选择性地催化氧化碳氢化合物,是细胞色素P-450的很好的模型化合物,但目前得到的铬(Ⅲ)卟啉配合物为数尚少。本文在三氯甲烷中用氧化-还原法从一氯四苯基卟啉合铬(Ⅲ)(配合物Ⅰ)合成了迭氮基吡啶四苯基卟啉合铬(Ⅱ)(配合物Ⅱ),培养了配合物Ⅱ的单晶,x-射线四圆衍射法测定了其晶体和分子结构。这是第一个得到的三价铬四苯基卟啉的分子结构。     

基于清洁氧源的金属卟啉配合物仿生催化氧化研究进展

细胞色素P-450是光面内质网上的一类含铁的膜整合蛋白, 其核心结构是铁卟啉配合物, 它是生命体中P-450酶系的末端氧化酶[1]. 金属卟啉配合物作为细胞色素P-450酶活性中心的类似物, 因其能够在温和条件下, 高活性、高选择性地催化烃类、醇类等有机底物的氧化, 而受到人们的广泛关注[2].     

新型中位不对称卟啉及其金属配合物的合成

在酶的参与下,许多生物氧化过程能在常温常压下进行,并具有高度的选择性。某些金属酶的活性中心是含有类似卟啉的金属配合物,它能在温和条件下活化分子氧和催化各种有机物的氧化反应。目前,各类金属卟啉及其衍生物已被广泛用作天然氧载体(例如血红蛋白)和加氧酶(如细胞色素 P-450单加氧酶)的模型化合物,因此,对其性质的研究具有十分重要的理论和实际意义。     

水溶性锰卟啉模拟酶体系快速混合停流谱研究

采用快速混合停流技术,考察了不同pH值条件下水溶性锰卟啉MnⅢ(TMPyP)与四种单氧给体m CPBA、KHSO5、NaOCl及H2O2构建的细胞色素P 450模拟酶体系催化氧化活性物种的生成及催化烯烃环氧化过程.低pH值时,主要生成四价锰氧中间体2;而在高pH值时,首先生成五价锰氧中间体1,该中间体再向四价中间体2转化.     

细胞色素P-450的化学模拟——酞菁铁(Ⅱ)光催化吖啶氮氧化物氧转移反应

在光的作用下,酞菁铁(Ⅱ)可催化吖啶氮氧化物的氧转移反应,将环己烯氧化成环氧化产物,成功地模拟了细胞色素P-450的选择性氧化烯烃的反应。观察到酞菁铁(Ⅱ)与吖啶氮氧化物形成配合物的紫外可见吸收。这是具有氧化性能的活泼中间体。比较了取代基性质对吖啶氮氧化物氧转移所生成的产物分布的影响,讨论了光催化氧转移反应机制。     

金属卟啉催化下环己烷羟基化反应中的Hammett关系

合成了40个卟啉环上具有不同取代基的单铁、锰卟啉和u-氧桥连双铁、锰卟啉,研究了这些金属卟啉模拟细胞色素P－450单充氧酶在温和条件下催化环己烷羟基化的反应.首次用线性自由能关系对金属卟啉仿生催化反应和金属卟啉自氧化反应进行相关分析,获得一些新的结果和规律.在此基础上,对金属卟啉仿生催化反应的可能机理进行了探讨.     

环己烷催化氧化制取顺酐和醋酸的催化剂研究

为研究气态环己烷催化氧化制取顺酐及醋酸的新反应，采取不同的方法制备了系列固体VPO催化剂.借助XRD、FT-IR对催化剂进行了主体晶相确定，用氧化还原滴定方法测定了不同晶相催化剂中钒的平均氧化数.结合催化反应的活性评价，发现催化剂主体晶相、结晶度、活化气氛和催化剂的V4＋/V5＋比均对目标反应的催化活性产生影响，5种催化剂中以(VO)2P2O7晶相催化剂的活性为最高.     

Kinetics and mechanistic study of the reaction of cyclic anhydrides with substituted phenols. Structure-reactivity relationships

[reaction: see text] The kinetic of the reactions of phthalic and maleic anhydrides with different substituted phenols (Z-PhOH with Z = H, m-CH(3), p-CH(3), m-Cl, p-Cl, and m-CN) were studied in aqueous solution. Two kinetic processes well separated in time were observed. The fast one is attributed to the formation of the aryl ester in equilibrium with the anhydride and allows the determination of the rate of nucleophilic attack of the phenol on the anhydride (k(-)(A)). From the slow kinetic process, the equilibrium constant for this reaction was determined. The Bronsted-type plots for the nucleophilic attack of substituted phenols on the anhydrides were linear with slopes beta(Nuc) of 0.45 and 0.56 for phthalic and maleic anhydride, respectively. The results are consistent with a mechanism involving rate-determining nucleophilic attack and also with a concerted mechanism. The calculated effective charge on the atoms involved in the reactions and the Bronsted beta values are consistent with a mechanism involving a concerted or enforced concerted mechanism where a tetrahedral intermediate with significant lifetime is not formed along the reaction coordinate. The latter mechanism is preferred over the stepwise process.     

2-(3,5-Diaryl-Δ4-1,3,4-thiadiazolin-2-yliden)-1,3-dithiole eine neue klasse elektronenreicher olefine

The dithiolium perchlorates 3a and b were smoothly converted into the phosphonium perchlorates 4a and b by reaction with tributylphosphin. Their deprotonation with butyllithium generates the methylen-phosphoranes 7 (not isolates), from which the electron-rich olefines 9a-d are obtained by successive treatment with the Δ⁴-1,3,4-thiadiazolium perchlorates 5d and e such as triethylamine. The olefine synthesis can be performed too by the reverse way, that is by the reaction of the phosphonium salts 6a-c with the dithiolium salts 3a and b under authentic conditions. In this way the electron-rich olefines 9e-h are obtained.     

金催化顺丁烯二酸酐的选择加氢反应

采用溶胶-凝胶法制备了一系列担载纳米金催化剂,用以催化顺丁烯二酸酐(简称顺酐,MA)的选择加氢反应．模板剂的引入改变了催化剂载体的结构,从而提高了其催化活性和对加氢产物丁二酸酐(SA)以及丁二酸二乙酯(DFAS)的选择性．同时考察了反应温度、溶剂、催化剂制备方法对顺酐选择加氢反应的影响以及催化剂的重复使用性能．实验结果表明,以焙烧处理除去模板剂十八胺的Au／SiO2-O(C)为催化剂时,顺酐选择加氢制取丁二酸酐和一步加氢酯化制取丁二酸二乙酯的效果最佳,其转化率以及产物选择性均大于99．5％．     

Kinetic study of the hydrolysis of phthalic anhydride and aryl hydrogen phthalates.

The kinetics of the hydrolysis of phthalic anhydride and X-phenyl hydrogen phthalate (X = H, p-Me, m-Cl, and p-Cl) were studied. Several bases accelerate the reaction of phthalic anhydride: acetate, phosphate, N-methyl imidazole, 1,4-diazabicyclo[2,2,2]octane (DABCO), and carbonate. Phosphate, DABCO, and N-methyl imidazole react as nucleophiles, whereas the data do not allow the determination of whether the other bases react in the same way or as general bases catalyzing the water reaction. The rate constants for all of them including water and HO- define a Br?nsted plot with beta = 0.46. The kinetics of the hydrolysis of the esters were studied below pH 6.20, and the mechanism involves the formation of phthalic anhydride, which then is hydrolyzed to the phthalic acid. Phenoxide ion has a very high rate constant for the reaction with phthalic anhydride, so above pH 6.20 it competes significantly with the hydrolysis of the anhydride. The reactions of the esters as a function of pH allow the determination of the kinetic pK(a) which are 3.06, 3.02, 2.95, and 2.93 for X = H, p-Me, m-Cl, and p-Cl, respectively. The data also show that the catalysis by the neighboring carboxy group takes place only when it is ionized (i.e., as carboxylate).     

Synthesis, characterization and analytical application of a hydroxamic acid resin

A chelating ion-exchange resin with hydroxamic acid functional groups was synthesized from styrene-maleic acid co-polymer cross-linked with divinylbenzene. A resin prepared from equimolar amounts of styrene and maleic anhydride with 0.75 mole% divinylbenzene gives the best sorption characteristics. The selectivity of the resin for metal ions is copper(II) > cobalt(II) > zinc(II) > nickel(II) > manganese(II) > chromium(III) > iron(III) > vanadium(V). Copper(II), chromium(III) and iron(III) in chromium plating baths can be separated by use of the resin and determined spectrophotometrically.     

A parametric study of the terminal maleation of polypropylene through an Alder Ene reaction

A study of the parameters that affect the Alder Ene reaction with respect to the synthesis of a terminally anhydride-functionalized polypropylene was carried out over a temperature range of 220–250°C using maleic anhydride concentrations of 2–12 mol equivalence with respect to the vinylidene group. As previously observed, a Lewis acid (i.e., SnCl₂ · 2H₂O) had a catalytic effect on the reaction at these temperatures, thereby improving anhydride content in the polymer for short reaction times. Increased temperature and maleic anhydride concentration had a positive effect on improving the incorporation of the succinyl anhydride moiety at the terminal site in polypropylene. Lower SnCl₂ · 2H₂O concentrations, likewise, improve the functionality of the product. The application of a second-order kinetic model to the measured succinyl anhydride results was not valid over the entire temperature range studied due to side reactions, particularly vinylidene isomerization, and homopolymerization of maleic anhydride. Ruthenium chloride has been examined as another possible catalyst candidate in the reaction and has been found to improve the level of anhydride incorporation in polypropylene compared to stannous chloride. © 1998 John Wiley & Sons, Inc. J. Polym. Sci. A Polym. Chem. 36: 2371–2380, 1998     

Über die reaktion von pyridin mit maleinsäureanhydrid-I

The reaction between pyridine and maleic anhydride was studied thermoanalytically. With reagents of high purity, the reaction proceeds very slowly with formation of oligomeric and polymeric products. Protic reagents (such as water, maleic acid, acetic acid or pyridinium hydrochloride) catalyse the reaction during which polymerization occurs at a later stage.Radical inhibitors (such as sulphur, 2,2-diphenyl-1-picryl hydrazyl or anthracene) have no influence on the reaction rate.Ultra-violet spectroscopic studies on solutions of maleic anhydride and some derivatives in pyridine and dimethyl sulphoxide show a charge-transfer absorption for the maleic anhydride/pyridine system at 303 nm.     

Solid-state synthesis of amphiphilic chitosan-polyethylene systems by the maleinization of both components

N-acylated chitosan modified by maleic anhydride was prepared by the method of the solid-state synthesis (Bridgman anvils, semipilot extruder). In contrast to the synthesis under homogeneous conditions, solid-state acylation is accompanied by the reaction of imidization of the formed amic acid as well as by reaction through double bonds, thus leading to the formation of derivatives of succinic anhydride. By simultaneous or subsequent interaction of chitosan modified with maleic anhydride with a PE matrix, either modified or not modified with maleic anhydride, new chitosan-polyethylene composite materials are prepared, and these composites are characterized by the combined valuable medicinal and biochemical properties of chitosan and high mechanical characteristics of the polyolefin component. The above composites are of obvious interest as amphiphilic sorbents, which are highly resistant to the action of aggressive media, as well as antimicrobial and biodegradable PE-based materials.     

Contribution to the study of the mechanism of curing of unsaturated polyester resins

The mechanism of copolymerization of monomethyl and dimethyl maleates and fumarates with styrene was studied by analysis of the conformation of the acid units of the resulting copolymers. The absorption bands for C?O stretching and OH stretching in the spectra of the copolymers are fully identical. They are quite different from the spectra of the copolymers obtained from maleic anhydride and styrene that are subsequently treated with absolute methanol to give the monoester which is then esterified with diazomethane to give the diester. The acid units of the copolymers derived from maleic anhydride exist in a gauche configuration; copolymers derived from fumaric units exist in a trans conformation. The identity of copolymers derived from maleic units with those derived from fumaric units but not with those derived from maleic anhydride indicates that the first step in the copolymerization of the maleic units is an isomerization to fumaric units, which are actually the genuine comonomers.