高碘酸钠催化微晶纤维素的氧化

主要讨论了使用高碘酸钠(NaIO4)溶液氧化微晶纤维素的过程及性能,用红外光谱(IR)验证了氧化纤维素的生成;通过扫描电镜(SEM)、热重分析(TG-DSC)以及X射线衍射(XRD)对比了反应前后纤维素的变化;考察了氧化时间、氧化温度、氧化剂的浓度以及溶液的pH值对氧化纤维素的产率及醛基含量的影响;结果表明,反应前后纤维素的晶型和形貌基本没有变化,随着氧化程度的加深,氧化纤维素的热稳定性越来越差;并且随着氧化温度的提高和氧化剂浓度的增大,醛基含量相应提高,而氧化时间和pH值对醛基含量存在相对最高值。     

纳米纤维素的制备

在纳米尺寸范围操控纤维素分子及其超分子聚集体,结构设计并组装出稳定的多重花样,由此创制出具有优异功能的新纳米精细化工品、新纳米材料,是纤维素科学的前沿领域和热点。为了研究当前制备纳米纤维素的现状和发展方向,简述了纳米纤维素化学基础,介绍了三类纳米纤维素：纳米纤维素晶体（晶须）、纳米纤维素复合物和纳米纤维素纤维,重点综述了纳米纤维素的五种制备方法：化学法制备纳米纤维素晶体和晶须、生物法制备细菌纤维素、物理法制备微纤化纳米纤维素、人工合成纳米纤维素和静电纺丝制备纤维素纤维,讨论了各种制备方法的优点和缺点,指出开展纳米纤维素超分子的可控结构设计、立体与位向选择性控制与制备、分子识别与位点识别等自组装过程机理、多尺度结构效应的形成机理等基础理论性研究是主要研究基础,新型的、绿色、低能耗、快速、高效的制备方法是纳米纤维素制备方法的发展方向。     

可持续高分子-纤维素新材料研究进展

21世纪"绿色"化学已成为世界各国社会经济发展中的研究与开发战略方向.纤维素是自然界中储量最丰富的天然高分子,是重要的可再生资源以及未来的主要工业原料.然而由于纤维素存在着大量的分子内以及分子间氢键,其结构致密,难以溶解或熔融进一步加工.本文简要介绍了近几年来关于直接使用物理溶剂方法(非衍生化)对纤维素材料开发利用的新进展,主要包括以下4个方面:(1)纤维素在"绿色"溶剂-碱/尿素以及离子液体体系中的溶解和再生;(2)纳米纤维素的制备以及组装;(3)木材纳米技术的开发及利用;(4)细菌纤维素基材料等,旨在推进"绿色"技术实现纤维素资源的研究开发及利用.     

基于纤维素的气凝胶材料

纤维素是自然界中储量最为丰富的一种天然高分子。作为继无机气凝胶和合成聚合物气凝胶之后的第三代气凝胶,纤维素基气凝胶材料兼具绿色可再生的纤维素材料和多孔气凝胶材料两者的优点,成为纤维素材料研究与应用中的一个热点。本文梳理了纤维素基气凝胶材料的发展脉络,综述了纤维素基气凝胶材料的研究进展。重点对纤维素基气凝胶的制备方法进行了总结,包括基于含水溶剂和无水溶剂的纤维素直接溶解法及源自植物纤维素和细菌纤维素的纤维素纳米纤维的水相分散法。介绍了纤维素基气凝胶力学性能的提高和功能性开发的最新研究结果。最后对纤维素基气凝胶材料的发展前景和研究方向进行了展望。     

EC/CA共混物的相容性和热稳定性

EC/CA共混物的相容性和热稳定性;乙基纤维素;醋酸纤维素;溶液共混;相容性     

纳米纤维素的制备及产业化

纳米纤维素因其独特的结构及优越的性能引起了学术和企业界的广泛关注与重视,日渐成为新材料和纤维素科学领域的研究热点。以木质纤维资源为原料,可分离出两种主要类型的纳米纤维素：纤维素纳米晶体（CNC）和纤维素纳米纤丝（CNF）。本文详细综述了CNC和CNF的制备方法,着重介绍了近几年新兴的制备方法,包括可回收的有机酸水解法综合制备CNC和CNF,美国高附加值制浆（AVAP）法制备木质素包覆的CNC和CNF,低共熔溶剂预处理结合机械剪切高效制备CNC和CNF,以及微极性环境下可调控机械剥离制备亲疏水性CNF等。同时,讨论了各种制备方法的优缺点,并介绍了国内外纳米纤维素的产业化研究进展。最后,我们提出纳米纤维素的制备方法未来将朝着绿色、高效和可持续的方向发展。     

纤维素在超临界水中的反应

纤维素是一种非常有价值的可再生资源,通过其反应可以获得多种有用的物质。对纤维素在超临界水中的反应进行了综述。在没有催化剂的情况下,纤维素在超临界水中水解生成葡萄糖、果糖、低聚物等;对纤维素水解的设备、产物分布以及纤维素水解反应机理进行了阐述。采用Ni,Pt,Ru,KOH等作催化剂,纤维素在超临界水中发生气化反应,生成的气体产物主要为H2,CO2和CH4;介绍了纤维素及其主要水解产物葡萄糖的制氢反应过程。对纤维素超临界水反应技术的发展前景进行了展望.     

纤维素在新型绿色溶剂离子液体中的溶解及其应用*

近年来,离子液体作为一种极具应用前景的绿色溶剂受到越来越多的关注。纤维素是自然界中含量最丰富的可再生资源,必将成为未来最重要的工业原料之一。离子液体在纤维素化学领域的应用遵循了绿色化学中开发环境友好溶剂和利用生物可再生资源为原料这两个基本原则,大大拓展了纤维素的工业应用前景,为纤维素资源的绿色应用提供了一个崭新的平台。本文对纤维素在离子液体中溶解的研究进展及其在制备再生纤维素材料、纤维素衍生物及生物乙醇等方面的应用进行了综述。纤维素大分子的降解机理及其控制途径、纤维素晶态结构变化规律及其调控途径、纤维素与固体反应试剂的均相衍生化体系的建立及提高衍生化效率的途径等基础问题仍需要进一步深入研究。     

纤维素苯基氨基甲酸酯的均相合成及其手性拆分性能评价

认识多糖类手性拆分材料的结构性能关系对于构建新型高效手性固定相具有重要指导意义。该文中,以1-烯丙基-3-甲基咪唑氯离子液体为介质,合成了系列不同结构的纤维素苯基氨基甲酸酯,进而考察了取代度、取代基团种类和位置对产物手性拆分性能的影响。结果表明,随着取代度的增加,纤维素苯基氨基甲酸酯对于绝大部分手性分子的拆分效果提高;苯环上取代基团的种类和位置对纤维素苯基氨基甲酸酯手性拆分性能影响显著,弱吸电子基团氯基和给电子基团甲基在合适的位置能显著增强纤维素苯基氨基甲酸酯的手性拆分性能;纤维素3-甲基-4-氯苯基氨基甲酸酯、3,5-二氯苯基氨基甲酸酯和2-甲基-5-氯苯基氨基甲酸酯对一些手性分子的拆分效果优于纤维素3,5-二甲基苯基氨基甲酸酯。     

过渡金属基催化剂降解纤维素应用研究进展

使用廉价过渡金属替代强酸和贵金属催化剂实现纤维素的高效转化是绿色化工的发展方向,一直是众多研究者关注的焦点。本文分别从纤维素热解(包括热解液化和热解气化)、纤维素水解、纤维素氢解和纤维素降解转化为5-羟甲基糠醛(5-HMF)等方面综述了过渡金属基催化剂在纤维素转化过程中的应用,从催化剂类型、反应条件和反应机理等方面介绍了过渡金属基催化剂催化的纤维素转化应用研究进展;最后,指出了催化过程中存在的问题,并对未来的研究方向进行展望。     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.