Ce(Ⅳ)盐引发丙烯酰胺在聚乙烯醇微球表面接枝聚合的研究

以硫酸铈铵为引发剂,采用水溶液聚合体系,在酸性介质中实施了丙烯酰胺(AM)在聚乙烯醇交联微球(CPVA)表面的接枝聚合,制备了接枝微粒CPVA-g-PAM,重点研究了各种因素对接枝聚合的影响规律,探讨了铈盐引发接枝聚合的机理.实验结果表明,在Ce(Ⅳ)盐的氧化作用下,在含有大量羟基的CPVA微球表面会产生自由基,顺利地实现丙烯酰胺的自由基接枝聚合反应.PAM的接枝度首先取决于水介质中硫酸的浓度,接枝度随硫酸浓度的增大呈现先增大后减小的变化规律,当H+离子浓度为0.36mol/L时,PAM的接枝度最高,酸浓度对接枝度的影响反映了铈盐引发接枝聚合的微观机理.引发剂Ce4+盐的浓度过大,将会促进氧化终止过程,降低接枝度,适宜的Ce4+盐浓度为5.98×10-3mol/L.在接枝聚合过程中,单体丙烯酰胺浓度和反应温度也会对接枝聚合产生影响.在本研究所确定的适宜条件下,可制得PAM接枝度为27.13g/100g的接枝微粒CPVA-g-PAM.     

接枝微球CPVA-g-PSSS的制备及其对5-氟尿嘧啶载药及体外结肠定位释药特性研究

在具有生物相容性的交联聚乙烯醇(CPVA)微球表面,采用铈盐-羟基氧化还原引发体系,实施了对苯乙烯磺酸钠(SSS)的表面引发接枝聚合,制得了接枝有聚阴离子的接枝微球CPVA-g-PSSS,采用红外光谱(FTIR)、扫描电子显微镜(SEM)及zeta电位测定等法,对接枝微球的化学结构及物理化学特性进行了表征.在此基础上重点考察分析了接枝微球CPVA-g-PSSS对5-氟尿嘧啶(5-FU)的吸附(载药)性能与吸附机理,考察探索了载药微球在不同pH介质中的释放行为.实验结果表明,羟基-铈盐氧化还原引发体系可有效地引发SSS在CPVA微球的表面接枝聚合,在适宜的反应条件下,可制得PSSS接枝度为16.1 g/100g的接枝微球CPVA-g-PSSS.在酸性介质中,受强静电相互作用的驱动,接枝微球CPVA-g-PSSS对5-FU分子表现出很强的吸附能力,吸附容量达105 mg/g,可实现有效载药.载药微球的释药行为具有强烈的pH依赖性,在pH=1的介质中,基本不释药;而在pH=7.4的介质中,则发生突释,表现出良好的结肠定位释放行为.     

铈盐引发丙烯腈在含醇羟基硅胶表面的接枝聚合

将偶联剂γ-(2,3-环氧丙氧基)丙基三甲氧基硅烷(EPPS)键合于硅胶微粒表面,在酸性催化剂作用下,键合EPPS的环氧键开环,产生了醇羟基(HXYG),形成表面带有醇羟基的改性微粒HXYG-SiO2.使用铈盐与硅胶表面的醇羟基构成氧化还原引发体系,在硅胶表面实施了丙烯腈的接枝聚合,制备了接枝微粒PAN-SiO2,考察了接枝聚合的影响因素.实验结果表明:在所形成的氧化还原引发体系中,由于初级自由基即引发物种处于硅胶微粒表面,所制备的接枝微粒PAN-SiO2具有高的接枝度(0.19 g/g),且单体的整体接枝效率高;引发剂铈盐的浓度对接枝度有较大的影响,铈盐浓度过大,将会促进氧化终止过程,降低接枝度,适宜的铈盐浓度为5.93×10-3mol/L;接枝度随硫酸浓度的增大呈现先增大后减小的变化规律,当H+离子浓度为0.38mol/L时,PAN的接枝度最高.     

构建巯基-Ce(Ⅳ)盐氧化还原引发体系实现丙烯腈在硅胶微粒表面的高效接枝聚合

使用偶联剂γ-巯丙基三甲氧基硅烷(MPMS,KH-590),对微米级硅胶微粒进行了表面化学改性,将巯基引入硅胶微粒表面(SiO2-MPMS),构成巯基-Ce(Ⅳ)盐氧化-还原引发体系,探索研究了丙烯腈在硅胶微粒表面的引发接枝聚合,制得了高接枝度(30 g/100g)的接枝微粒SiO2-MPMS-g-PAN.采用红外光谱(FTIR)、扫描电镜(SEM)及热重分析(TGA)等方法对接枝微粒SiO2-MPMS-g-PAN进行了表征.在此基础上,重点研究了主要因素对巯基-Ce(Ⅳ)盐体系引发AN接枝聚合的影响.研究结果表明,类似于羟基-Ce(Ⅳ)盐体系,巯基-Ce(Ⅳ)盐体系也可以有效地引发乙烯基单体在固体微粒表面接枝聚合.与在固体微粒表面引入可聚合双键的"grafting through"接枝聚合法相比,铈盐引发的接枝聚合,由于活性位点居于载体表面,故具有高的接枝度,是一种高效率的表面引发接枝法.为制得高接枝度的接枝微粒SiO2-MPMS-g-PAN,本研究体系适宜的酸浓度为0.25 mol/L;Ce(Ⅳ)盐浓度为5.0×10-3 mol/L;接枝聚合宜在50℃下进行.     

利用接枝微球CPVA-g-PMAA与酮洛芬分子间的氢键相互作用构建结肠定位释药体系

通过表面引发接枝聚合,在交联聚乙烯醇（CPVA）微球表面实施了甲基丙烯酸（MAA）的表面引发接枝聚合,制备了高接枝度的接枝微球CPVA-g-PMAA。利用接枝微球CPVA-g-PMAA与酮洛芬（KPF）主-客体之间的氢键相互作用构建结肠定位释药体系。分析了接枝微球CPVA-g-PMAA对KPF的吸附（载药）性能与吸附机理,深入研究了载药微球在不同pH介质中的释放行为。实验结果表明,在酸性介质中,受主-客体之间强氢键作用的驱动,接枝微球CPVA-g-PMAA对KPF分子表现出强吸附能力,吸附容量接近10mg/g,可实现有效载药。载药微球的释药行为具有强烈的pH依赖性,在pH=1的介质中,释药程度很低;而在pH=7.4的介质中,则发生突释,表现出良好的结肠定位释放行为。     

高性能胰蛋白酶分子表面印迹材料的制备及其大分子识别特性研究

以交联聚乙烯醇(CPVA)微球为基质,以甲基丙烯酸(MAA)为功能单体,在中性水介质中制备了高性能胰蛋白酶(TRY)大分子表面印迹材料。首先通过CPVA微球表面的羟基与甲基丙烯酰氯之间的酯化反应,将大量可聚合双键甲基丙烯酰基(MAO)引入微球表面,获得改性微球MAO-CPVA。在中性水溶液中,单体MAA的羧基几乎发生完全电离,凭借强烈的静电相互作用,MAA自动结合在碱性蛋白TRY大分子周围,形成单体-模板复合体。水溶液中过硫酸铵/亚硫酸氢钠引发体系所产生的自由剂,使包围在TRY周围的单体MAA与交联剂N,N'-亚甲基双丙烯酰胺(MBA)在微球MAO-CPVA表面发生接枝交联聚合,而模板TRY则被包裹在交联网络之中,除去模板后便得到了TRY表面印迹微球MIP-PMAA/CPVA。深入考察了该表面印迹微球的大分子识别性能。研究结果表明,表面印迹微球MIP-PMAA/CPVA对TRY具有优良的结合亲和性,结合容量高达84mg·g~(-1)(3.6μmol·g~(-1));对模板蛋白TRY具有特异的识别选择性,相对于另一种碱性蛋白木瓜蛋白酶,印迹微球对TRY的选择性系数高达21.62。     

5-氟尿嘧啶分子表面印迹微球MIP-PSSS/CPVA的制备及其体外结肠定位释药特性研究

以对苯乙烯磺酸钠(SSS)为功能单体, 以N,N'-亚甲基双丙烯酰胺(MBA)为交联剂, 采用铈盐-羟基氧化还原引发体系, 在交联聚乙烯醇(CPVA)微球表面实施了5-氟尿嘧啶(5-FU)分子的表面印迹, 在微球CPVA表面形成印迹聚合物(MIP)层, 即制备了5-FU分子印迹微球MIP-PSSS/CPVA. 采用红外光谱(FTIR)和扫描电子显微镜(SEM)法, 对印迹微球进行了表征. 重点考察分析了印迹微球对5-氟尿嘧啶(5-FU)的结合(载药)性能与结合机理, 考察探索了载药微球在不同pH介质中的释放行为. 实验结果表明, 基于本体系特殊的羟基-铈盐表面引发体系, 可有效地实现5-FU分子的表面印迹, 在微球CPVA表面形成分布有大量5-FU分子印迹空穴的聚合物层. 在酸性介质中, 受强静电相互作用的驱动, 印迹微球MIP-PSSS/CPVA对5-FU分子表现出很强的结合能力, 结合容量达110 mg/g, 可实现有效载药. 载药微球的释药行为既具有强烈的pH依赖性, 又具有时滞性: 在模拟胃液中(pH＝1), 基本不释药; 在模拟小肠液中(pH＝6.8), 释药量很小; 在模拟结肠液中(pH＝7.4), 则发生突释, 表现出高效的结肠定位释放行为.     

表面引发接枝聚合法制备高接枝度的接枝微粒SiO2-g-PMAA

将偶联剂γ-氨丙基三甲氧基硅烷(AMPS)键合在硅胶微粒表面,得到改性微粒AMPS-SiO2;使改性微粒表面的氨基与溶液中的过硫酸铵构成氧化-还原引发体系,实现了甲基丙烯酸(MAA)在硅胶微粒的表面引发接枝聚合,制得了高接枝度(0.30 g/g)的接枝微粒SiO2-g-PMAA;研究了影响表面引发接枝聚合的主要因素。 结果表明,适宜的温度为40 ℃。 已接枝到硅胶表面的聚合物层对后续的接枝聚合产生阻隔作用。 适宜的引发剂用量为单体质量的1.1%,适宜的单体质量分数为5%左右。     

氨基-铈盐氧化还原体系引发对苯乙烯磺酸钠在硅胶微粒表面的接枝聚合

使用偶联剂γ-氨丙基三甲氧基硅烷(AMPS)对微米级硅胶微粒进行表面化学改性,将氨基引入硅胶微粒表面,构成氨基-Ce(Ⅳ)盐氧化-还原引发体系。研究了在其作用下对苯乙烯磺酸钠(SSS)在硅胶微粒表面的接枝聚合,制得了具有较高接枝度(18g/100g)的接枝微粒PSSS/SiO2。采用FTIR、SEM及TGA等方法对接枝微粒进行表征。考察了对该表面引发接枝聚合体系接枝度影响的主要因素。结果表明,氨基-Ce(Ⅳ)盐体系可以有效地引发乙烯基单体在固体微粒表面的接枝聚合,氨基的质子化对产生自由基的引发步骤具有负影响;为提高PSSS的接枝度,引发剂溶液(铈盐+硫酸)宜采用滴加的方式加入;适宜的单体浓度为14(wt)%;接枝聚合宜在50℃下进行。接枝微粒PSSS/SiO2是一种功能复合微粒,凭借离子交换作用,对重金属离子和稀土离子均可产生强的吸附作用。     

茶碱分子表面印迹微球的制备及其体外释药性能

通过分子表面印迹技术,采用铈盐-羟基氧化还原引发体系,以交联聚乙烯醇(CPVA)微球为基质、对苯乙烯磺酸钠(SSS)为功能单体、茶碱(TP)为模板药物分子、N,N′-亚甲基双丙烯酰胺(MBA)为交联剂,制备了TP分子表面印迹微球MIP-PSSS/CPVA。采用红外光谱测定其结构,扫描电镜观察其表面形貌,静态法考察印迹微球MIP-PSSS/CPVA对TP的结合性能及载药印迹微球的体外释药行为。结果表明:TP分子表面印迹微球MIP-PSSS/CPVA对TP具有较高的识别选择性和结合亲合性,当pH=1时,微球对TP的结合容量达到92mg/g。该印迹微球在模拟胃液中基本不释药;在模拟小肠液中的第2~6h,累积释放率仅为21%;而在模拟结肠液中突释,之后持续缓慢地释放,表现出优良的pH敏感和时滞双重型结肠定位释药特性。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.