NdCl_3·3P350-AlR_3二元催化体系对双烯烃的定向聚合

由氯化稀土的不同种类磷酸酯配合物与三烷基铝组成的Ziegler-Natta催化剂对双烯烃聚合的研究已有报道,其中聚合活性最高的NdCl_3·3P350—AlR_3二元催化体系对丁二烯溶液聚合及异戊二烯本体聚合的详细研究尚未见报道,本文考察了该体系对双烯烃的定向聚合能力,通过二元体系与相应的催化剂活性体聚合规律的对比,提高对稀土催化聚合反应过程的认识。     

一苯氧基二氯化钕四氢呋喃络合物和三氯化钕酚合物对丁二烯聚合的催化活性

<正> 脂肪族三烷氧基稀土化合物作为双烯烃定向聚合的主催化剂只有少数专利。最近,单成基等以Nd(OR)_(3-n)Cl_n-AlEt_3催化体系对双烯烃聚合进行了研究。三氯化钕醇合物与烷基铝组成的双烯烃聚合催化体系已有报导。本文着重研究一苯氧基二氯化钕四氢呋喃络合物和三氯化稀土酚合物与烷基铝组成的催化体系对丁二烯聚合的催化活性。     

有关氯化钕磷酸三丁酯体系的活性及其与烷基铝反应的研究

稀土羧酸盐,如辛酸盐,硬酯酸盐和环烷酸盐等组成的催化体系对共轭双烯烃聚合具有良好的活性和定向效应。但体系中要有第三组分的存在,通常采用的是烷基氯化铝,其作用是与羧酸盐羧基进行交换反应,是形成活性中心的必要条件。氯化稀土组成的体系由于自身组成含有氯离子而排除了第三组分的使用,从而简化了聚合工艺流程,有利于研究体系组分之间的反应。但是并非所有氯化稀土都适宜于这种研究,原因在于大多数氯化稀土络合物不溶于惰性有机溶剂。如氯化稀土醇合物对共轭双烯烃聚合有着相当高的活性,但是研究氯化稀土醇合物与烷基铝的反应却有着一定的困难。     

离子液体中氯化稀土催化ε-己内酯开环聚合

 在离子液体中进行了无水氯化稀土催化ε-己内酯(ε-CL)的开环聚合,并考察了不同氯化稀土、环氧化物、环氧化物/氯化稀土摩尔比、单体浓度、单体/氯化稀土摩尔比、反应温度和时间对聚合的影响. 结果表明,无水氯化稀土/环氧化物能有效地催化ε-己内酯在离子液体中进行开环聚合, GdCl3和ErCl3的催化活性比其他稀土氯化物高.当温度为60 ℃, 环氧丙烷/ErCl3的摩尔比为30时, ε-CL 在离子液体［bmim］BF4中聚合30 min, 单体的转化率可达到96.0%, 粘均分子量(Mv)为2.54×104. 分别采用NMR和示差扫描量热对聚合物的结构和热性能进行了表征. 结果表明, ε-CL 在离子液体中发生了酰氧键断裂,聚合的机理是配位-插入机理.     

Nd(OR)_(3-n)Cl_n-AlEt_3催化体系对丁二烯的聚合 Ⅰ.聚合的一般规律

本文提出了一类新型稀土定向聚合催化体系Nd(OR)_(3-n)Cl_n-AlEt_3。通过一系列基本实验,从多方面考查了以该体系催化的丁二烯聚合的规律。结果表明,当n=2时,该催合体系对聚丁二烯微观结构的影响类似于三元催化体系Nd(OR)_3-Al_2Et_3Cl_3-AlEt_3,但前者的活性较后者高,这使我们有可能应用较简单的二元体系来代替三元催化体系。     

二(三氟乙酸)卤化钕催化体系中卤素对催化共轭双烯烃聚合的影响

众所周知,稀土配位催化剂用于共轭双烯的定向聚合,卤素是形成活性中心的必要条件之一。文献上对卤素在稀土催化剂中的作用曾有研究,但报导的都是非均相催化体系和三元催化体系。均相的二元催化体系中的卤素作用尚未见文献报导。鉴于从可溶性(CF₃COO)₂NdClEtOH-Et₃Al体系中分离出含卤素原子的活性体,研究卤素在该体系中的作用,对于活性催化剂的形成条件和催化聚合反应机制的了解都有意义。     

丁二烯在NdCl_3·2Phen-HAl(i-Bu)_2催化体系下的聚合动力学

氯化稀土的某些配合物与烷基铝组成的双烯烃定向聚合催化剂用于丁二烯聚合时,大多得到分子量较高的产物。最近我们报道了可在较宽范围内改变聚丁二烯分子量的三氯化钕邻菲啰啉配合物(NdCl_3·2Phen)与氢化二异丁基铝[HAl(i-Bu)_2]所组成的新的二元氯化稀土定向聚合催化剂。本文报导该体系下的丁二烯聚合动力学,测定了聚合反应速率对     

稀土膦酸酯盐-烷基铝体系催化正辛基异氰酸酯配位聚合

报道了由稀土膦酸酯盐-烷基铝组成的催化体系在温和条件下催化正辛基异氰酸酯(n-OctNCO)的配位聚合特征. 研究发现, 以Nd(P204)3/Al(i-Bu)3组成的稀土催化体系是正辛基异氰酸酯聚合的良好催化剂. 系统考察了正辛基异氰酸酯在该催化体系下的本体、溶液聚合的聚合规律和溶液聚合反应动力学. 用1H NMR, FTIR, DSC, TGA和GPC等分析测试手段对所得到的聚合物进行了表征.     

Nd(naph)3-Al(i-Bu)3体系催化丙烯酸乙酯及丙烯酸亚丁酯聚合

丙烯酸酯类极性单体的聚合反应通常采用自由基型引发剂。过渡金属化合物与烷酸铝所组成的配位催化剂对这类极性单体的催化聚合迄今仍处于研究阶段。我们在稀土催化环氧烷烃聚合的基础上曾研究了稀土钕的磷酸盐体系催化甲基丙烯酸甲酯、正丁酯的聚合。本文研究了环烷酸钕体系催化丙烯酸乙酯及丙烯酸正丁酯的聚合特征。     

稀土催化剂的性质——添加不同结构的化合物对丁二烯聚合的影响

探讨了一系列不同结构和极性的化合物对以稀土催化的丁二烯聚合的影响。这些添加剂中绝大多数降低了催化活性,并使聚合物的分子量上升,而只有烯丙基衍生物虽然降低了催化活性,却使聚合物的分子量下降。从稀土催化剂的活性中心寿命很长和其对普遍用于Ziegler-Natta催化体系的调聚剂的不敏感性看来,稀土催化体系具有一定的特点,其聚合机理有可能与一般过渡金属催化体系不尽相同。     

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.