羟基喹啉偶氮类化合物的互变异构与顺反异构的研究

本工作合成了数种带不同取代苯基的羟基喹啉偶氮类化合物。对它们在不同溶剂。不同酸碱度溶液中的偶氮式及腙式间互变异构平衡进行了研究。苯环上不同取代基的引入可引起平衡发生变化。拉电子基的引入有利于腙式结构的形成,而推电子基的引入则对偶氮的生成影响不大。此外,工作中还发现:羟基喹啉偶氮化合物在光照下存在着以偶氮顺-反异构化反应为主的变化过程。     

芳族硝基化合物的电还原反应性能及其机理研究

采用循环伏安、线性扫描以及恒电位电解等测试方法,对o,m,p-氯硝基苯,o,m,p-硝基甲苯、o,m-硝基苯甲酸等八种芳族硝基化合物在硫酸-乙醇水溶液中的电还原性能及其机理进行了研究.结果表明,芳族硝基化合物在苯环上的取代基位置不同以及在相同位置上取代基的种类不同均可使各芳族硝基化合物的电还原性能发生较大差异;吸电子取代基在电还原过程中电位较正,推电子取代基的电还原电位较负;邻位取代基在反应过程中由于空间位阻效应,苯环上的硝基在电还原时电位往负方向移动.在电还原过程中,还原峰电流和表观活化能的大小均与取代基的电子效应和空间位阻相关,同时取代硝基氯苯得3个电子将还原生成氧化偶氮苯类化合物:邻、间硝基甲苯、硝基苯甲酸得4个电子将还原生成酚类化合物;对硝基甲苯得6个电子将还原生成胺类化合物,在此基础上,探讨了各芳族硝基化合物的电还原机理.     

硝酮化合物对9—氰蒽荧光猝灭作用的研究

本工作对硝酮化合物猝灭－氰蒽荧光的机制进行了研究。发现不同的９－氰蒽／硝酮体系可能经历包括电子转移，能量转移及竞争吸收等不同的猝灭过程，其中α，Ｎ－二苯基硝酮对荧光猝灭遵循电子转移机制，分别形成猝灭剂和敏化剂的离子自由基，但硝酮正离子自由不能导致环化反应发生。结果还表明：硝酮化合物的四π电子１，３偶极结构在猝灭过程中起主要作用，因此当光环化反应破环１，３偶极结构生成氧氮丙啶时，即失去其原有的猝灭能     

取代螺吡喃类化合物的合成及其光致变色性能

选取了具有代表性的取代基合成了带有不同取代基的系列螺吡喃类化合物,并对这些化合物进行了光响应研究以及动力学实验,考察其对光致变色性能的影响,以期发现取代基对该光致变色化合物的影响规律。结果表明:苯并吡喃环侧引入吸电子基且在二氢吲哚侧引入供电子基,所制化合物表现出优异的光致变色性能。     

硝酮化合物对9－氰蒽荧光猝灭作用的研究

本工作对硝酮化合物猝灭９－氰蒽荧光的机制进行了研究，发现不同的９－氰蒽／硝酮体系可能经历包括电子转移、能量转移及竞争吸收等不同的猝灭过程。其中α，Ｎ－二苯基硝酮对荧光猝灭遵循电子转移机制，分别形成猝灭剂和敏化剂的离子自由基，但硝酮正离子自由基不能导致环化反应发生，结果还表明：硝酮化合物的四π电子１，３偶极结构在猝灭过程中起主要作用，因此当光环化反应破环１，３偶极结构生成氧氮丙啶时，即失去其原有的猝灭能力，导致已被猝灭的荧光重新回复。     

苯并咪唑衍生物的合成研究

以邻苯二胺与醛为原料,采用盐酸作催化剂,空气为氧化剂,乙醇作溶剂,合成苯并咪唑衍生物,发现芳醛上带有吸电子基时则能够较好地得到目标产物,而芳醛上带有供电子取代基时,反应产物大多为双Schiff碱副产物。其中5个化合物为新化合物,产物结构经1H NMR确证。     

Friedlnder缩合反应合成C-2-β-D-葡萄糖基喹啉

采用葡萄糖和2,4-戊二酮经Knoevenagel缩合反应制备得到β-丙酮基葡萄糖,β-丙酮基葡萄糖与苯环取代的邻氨基苯甲醛经Friedlnder缩合反应,以高达90%的产率合成了4个结构新颖的葡萄糖基喹啉类化合物.目标化合物的结构均经1HNMR,13CNMR和元素分析确证。     

2-(取代乙炔基)苯甲醛衍生物在有机合成中的应用

作为一类具有特殊结构的重要有机合成中间体，2-(取代乙炔基)苯甲醛衍生物的化学结构是由苯环、取代乙炔基和醛基三部分活性基团构成的共轭体系. 因其具有较高的反应活性，而被广泛的用于构建各种具有新颖结构的苯并碳环或苯并杂环类化合物，如苯并碳环化合物、苯并氮杂环化合物、苯并氧杂环化合物、多元苯并杂环化合物等. 本文综述了2-(取代乙炔基)苯甲醛衍生物在有机合成领域的应用，并对其发展前景进行了展望，为今后2-(取代乙炔基)苯甲醛衍生物在有机合成中的应用提供参考.     

多供电子基苯胺类化合物的合成及其芳基五唑衍生物稳定性

合成了6个含多供电子基的苯胺类化合物,为合成更稳定的芳基五唑提供了原料。合成过程中,以CMC稳定的纳米铁颗粒为还原剂,以[DMFH]H2PO4为催化剂,还原芳香族硝基化合物,改进了铁粉还原产生大量废水、铁泥的缺点,使反应更加绿色环保;此外,还原以对氨基苯磺酸制得的偶氮化合物,合成得到所需的苯胺类化合物。并通过量子化学方法计算了芳基五唑衍生物分解所需的能量壁垒,以此为依据,比较了苯环上供电子基的数量及不同位置对芳基五唑化合物稳定性的影响。苯环上间、对位的供电子基有利于芳基五唑的稳定,供电子基在对位时对稳定性的影响要强于间位,邻位的供电子基增大了空间位阻,不利于芳基五唑的稳定。     

多供电子基苯胺类化合物的合成及其芳基五唑衍生物稳定性

合成了6个含多供电子基的苯胺类化合物,为合成更稳定的芳基五唑提供了原料。合成过程中,以CMC稳定的纳米铁颗粒为还原剂,以[DMFH]H2PO4为催化剂,还原芳香族硝基化合物,改进了铁粉还原产生大量废水、铁泥的缺点,使反应更加绿色环保;此外,还原以对氨基苯磺酸制得的偶氮化合物,合成得到所需的苯胺类化合物。并通过量子化学方法计算了芳基五唑衍生物分解所需的能量壁垒,以此为依据,比较了苯环上供电子基的数量及不同位置对芳基五唑化合物稳定性的影响。苯环上间、对位的供电子基有利于芳基五唑的稳定,供电子基在对位时对稳定性的影响要强于间位,邻位的供电子基增大了空间位阻,不利于芳基五唑的稳定。     

Nucleobase-Derived Nitrones: Synthesis and Antioxidant and Neuroprotective Activities in an In Vitro Model of Ischemia–Reperfusion

Herein, we report the synthesis, antioxidant, and neuroprotective properties of some nucleobase-derived nitrones named 9a–i. The neuroprotective properties of nitrones, 9a–i, were measured against an oxygen-glucose-deprivation in vitro ischemia model using human neuroblastoma SH-SY5Y cells. Our results indicate that nitrones, 9a–i, have better neuroprotective and antioxidant properties than α-phenyl-N-tert-butylnitrone (PBN) and are similar to N-acetyl-L-cysteine (NAC), a well-known antioxidant and neuroprotective agent. The nitrones with the highest neuroprotective capacity were those containing purine nucleobases (nitrones 9f, g, B = adenine, theophylline), followed by nitrones with pyrimidine nucleobases with H or F substituents at the C5 position (nitrones 9a, c). All of these possess EC₅₀ values in the range of 1–6 μM and maximal activities higher than 100%. However, the introduction of a methyl substituent (nitrone 9b, B = thymine) or hard halogen substituents such as Br and Cl (nitrones 9d, e, B = 5-Br and 5-Cl uracil, respectively) worsens the neuroprotective activity of the nitrone with uracil as the nucleobase (9a). The effects on overall metabolic cell capacity were confirmed by results on the high anti-necrotic (EC_50′s ≈ 2–4 μM) and antioxidant (EC_50′s ≈ 0.4–3.5 μM) activities of these compounds on superoxide radical production. In general, all tested nitrones were excellent inhibitors of superoxide radical production in cultured neuroblastoma cells, as well as potent hydroxyl radical scavengers that inhibit in vitro lipid peroxidation, particularly, 9c, f, g, presenting the highest lipoxygenase inhibitory activity among the tested nitrones. Finally, the introduction of two nitrone groups at 9a and 9d (bis-nitronas 9g, i) did not show better neuroprotective effects than their precursor mono-nitrones. These results led us to propose nitrones containing purine (9f, g) and pyrimidine (9a, c) nucleobases as potential therapeutic agents for the treatment of cerebral ischemia and/or neurodegenerative diseases, leading us to further investigate their effects using in vivo models of these pathologies.     

Ability of nitrones of various structures to control the radical polymerization of styrene mediated by in situ formed nitroxides

The ability of several nitrones to control the radical polymerization of styrene at 110 °C has been investigated by high-throughput experimentation. The nitrone/free radical initiator pair dictates the structure of the nitroxide and the alkoxyamine formed in situ, which determines the position of the equilibrium between the active and the dormant species operating in the nitroxide-mediated polymerization. For the styrene polymerization to be controlled, the nitrone must be reacted with 2,2′-azo-bis-isobutyronitrile (AIBN) at 85 °C, prior to addition of styrene and polymerization at 110 °C. The effect of the nitrone structure on the kinetics of the styrene polymerization has been emphasized. Amongst all the nitrones tested, those of the C-phenyl-N-tert-butylnitrone (PBN) type are the most efficient in terms of polymerization rate, control of molecular weight and polydispersity. Electrophilic substitution of the phenyl group of PBN by either an electrodonor or an electroacceptor group has only a minor effect on the polymerization kinetics. Importantly, the polymerization rate is not governed by the thermal polymerization of styrene but by the alkoxyamine formed in situ during the pre-reaction step. The initiation efficiency is, however, very low, consistent with a limited conversion of the nitrone into nitroxide and alkoxyamine.     

Synthese,Struktur und photophysikalische Eigenschaften von polyarylierten Imidazolen und Oxazolen

Synthesis, Structure, and Photophysical Properties of Polyarylated Imidazoles and Oxazoles 23 tetraphenylimidazoles 1,2 and 11 triphenyloxazoles 4,5 with amino, nitro, methoxy, hydroxy, or halogeno substituents chiefly in the para position were prepared. The absorption and fluorescence emission properties were investigated in ethanolic solution. The effects of the substituents in 1,2 on the spectral shifts show that the arrangement of the phenyl rings in 1 position is not coplanar in relation to the heterocycle whereas the phenyl rings in 2 position are more coplanar. The spectral changes of compound 2a in solvents of various polarity (dielectric constants 2,02–47,24) are almost negligible. The Stokes shift is moderately increased. A remarkable increase in the fluorescence quantum yield is observed by chlorine substitution in phenyl ring 2.     

Computational modelling of the influence of substituent effects on phthalimidylazo disperse dye hydrolysis and interaction energy

Six azo dyes have been synthesised using N‐substituted phthalimides as diazo components. Substitution effects on dye hydrolysis and intermolecular interactions were investigated with density functional theory (DFT) at B3LYP/6‐311G level. The results showed that the phthalimide moieties adopted a coplanar conformation in respect of the azo‐coupled phenyl rings in all six dyes. N‐Alkyl substitution had little influence on the absorption maxima. Bromo and cyano substitution on the phthalimide ring resulted in hypsochromic and bathochromic shifts of the absorption maxima respectively. Hydrolysis of the phthalimide ring was found to be largely influenced by steric effects rather than inductive effects of substituents. It was also found that π‐stacking interactions of phthalimide/phenyl and phthalimide/phthalimide dimers were promoted by substituents. The results indicated that interactions are dominated by electrostatic and even more importantly dispersion forces. The computational results were also confirmed experimentally.     

Cycloadditions of Trans-Cyclooctenes and Nitrones as Tools for Bioorthogonal Labelling

Trans-cyclooctenes (TCOs) represent interesting and highly reactive dipolarophiles for organic transformations including bioorthogonal chemistry. Herein we show that TCOs react rapidly with nitrones and that these reactions are bioorthogonal. Kinetic analysis of acyclic and cyclic nitrones with strained-trans-cyclooctene (s-TCO) shows fast reactivity and demonstrates the utility of this cycloaddition reaction for bioorthogonal labelling. Labelling of the bacterial peptidoglycan layer with unnatural d -amino acids tagged with nitrones and s-TCO-Alexa488 is demonstrated. These new findings expand the bioorthogonal toolbox, and allow TCO reagents to be used in bioorthogonal applications beyond tetrazine ligations for the first time and open up new avenues for bioorthogonal ligations with diverse nitrone reactants.     

13C-kernmagnetische Resonanzspektren der Phenylfulgide

Carbon-13 Nuclear Magnetic Resonance Spectra of Phenylfulgides The carbon-13 chemical shifts are determined in a series of phenylfulgides in order to investigate steric and electronic influences of substituents. By means of the shift differences between suitably substituted compounds results can be obtained as to the relative variation of the rotation angles of the phenyl rings as well as to te angle alterations between the exocyclic double bonds and the anhydride ring. Introducing 4-CH₃O- and 4-NO₂-groups at the phenyl rings the substituent induced alterations of the carbon-13 chemical shifts and the π-polarization effects related with it are discussed.     

Some properties of poly(carbonates) and poly(thiocarbonates) from diphenols with methyl groups in the 3-position in the phenyl rings

Glass transition temperatures and the corresponding activation energies of poly(carbonates) and poly(thiocarbonates) with different side-chain substituents obtained from diphenols with methyl groups in the 3-position in the phenyl rings have been determined by differential scanning calorimetry at several scanning speeds. Partial specific volume and specific refractive index increments have also been obtained by densimetry and refractometry measurements in benzene at 25°C. The effect of the different substituents on these properties has been analysed. © 1998 SCI.     

Synthesis and Quantitative Structure–Activity Relationships of Selective BCRP Inhibitors

The breast cancer resistance protein (BCRP/ABCG2) is a member of the ABC transporter superfamily. This protein has a number of physiological functions, including protection of the human body from xenobiotics. The overexpression of BCRP in certain tumor cell lines causes cross‐resistance against various drugs used in chemotherapeutic treatment. In a previous work we showed that a new class of compounds derived from XR9576 (tariquidar) selectively inhibits BCRP. In this work we synthesized more members of this class, with modification on the second and third aromatic rings. The inhibitory activities against BCRP and P‐gp were assayed using a Hoechst 33342 assay for BCRP and a calcein AM assay for P‐gp. Finally, quantitative structure–activity relationships for both aromatic rings were established. The results obtained show the importance of the electron density on the third aromatic ring, influenced by substituents, pointing to interactions with aromatic residues of the protein binding site. In the second aromatic ring the activity of compounds is influenced by the steric volume of the substituents.     

Photocontrol of the refractive index of poly(methyl methacrylate) with a nitrone additive

Hydroxy‐substituted aromatic nitrone derivatives were used for the photochemical control of the refractive index of poly(methyl methacrylate) (PMMA) films. Upon irradiation with 366‐nm light in solution, these derivatives underwent rearrangement reactions, which eventually produced N,N‐diarylformamide derivatives in quantitative yields. Similar photoreactions of the aromatic nitrones in the PMMA films lowered the refractive index of the films by as much as 0.014. The magnitude of the observed refractive‐index change was enough for hydroxy‐substituted nitrones to be used as additives for the fabrication of graded‐index‐type polymer optical fibers. In addition, the refractive index of the PMMA films remained almost constant at any conversion of the starting nitrone derivatives for at least 70 days at room temperature. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2517–2520, 2004     

Exploring Chemical Substructures Essential for hERG K+ Channel Blockade by Synthesis and Biological Evaluation of Dofetilide Analogues

In this study we followed a new approach to analyze molecular substructures required for hERG channel blockade. We designed and synthesized 40 analogues of dofetilide ( 1 ), a potent hERG potassium channel blocker, and established structure–activity relationships (SAR) for their interaction with this important cardiotoxicity‐related off‐target. Structural modifications to dofetilide were made by diversifying the substituents on the phenyl rings and the protonated nitrogen and by varying the carbon chain length. The analogues were evaluated in a radioligand binding assay and SAR data were derived with the aim to specify structural features that give rise to hERG toxicity.