杂多酸引发四氢呋喃开环聚合反应Ⅵ.以环氧氯丙烷为促进剂

在以低浓度杂多酸(ＨＰＡ)催化四氢呋喃(ＴＨＦ)聚合反应中,我们曾采用环氧乙烷(ＥＯ)和环氧丙烷(ＰＯ)为促进剂,发现它们都具有很好的促进效果[1,2],并且活性相近.在以三氟化硼(ＢＦ3)为催化剂的四氢呋喃正离子开环聚合反应中,促进剂的活性次序为:ＥＣＨ(环氧氯丙烷)>ＰＯＥＯ[3].在ＨＰＡ催化ＴＨＦ聚合反应中,ＥＣＨ是否仍具有高的促进活性是本文研究的目的.1　原料及聚合操作ＴＨＦ的纯化见文献[4],ＥＣＨ的纯化见文献[5],十二磷钨杂多酸(ＰＷ12)的处理见文献[1],三氟醋酸酐的合成方法和聚合反应的操作均见前文[2].2　分析测试核磁共振…     

杂多酸引发四氢呋喃开环聚合反应 Ⅳ.以环氧丙烷为促进剂

对杂多酸引发四氢呋喃开环聚合的研究从八十年代中期开始已有不少报道［１～４］,其引发聚合的活性低,当杂多酸浓度低时,聚合反应时间长,产物分子量高;而为制得工业通常使用的中等分子量四氢呋喃聚醚二醇,需要加大量的引发剂,且聚合收率低（最高仅为３５％）．针对以上问题,本实验室曾对以环氧乙烷（ＥＯ）促进低浓度十二磷钨杂多酸Ｈ３ＰＷ１２Ｏ４（ＰＷ１２）引发四氢呋喃开环聚合反应进行了系统的研究［５,６］,发现ＥＯ对ＴＨＦ聚合具有良好的促进效果,制得中等分子量聚醚二醇,转化率达到６０％以上．本文进一步研究了环氧…     

EO／THF无规共聚醚结构研究（Ⅰ）—端羟基液体共聚醚的NMR分析

用核磁共振技术研究了环氧乙烷（ＥＯ）与四氢呋喃（ＴＨＦ）端羟基液体共聚醚（ＴＥＯ）的链结构，定量测定了ＴＥＯ的结构组成参数以及二元组与三元组序列分布。实验结果表明，端羟基液体ＴＥＯ易形成以Ｅ－ＯＨ为端基的线型无规交替结构，且序列分布随ＥＯ／ＴＨＦ组成比而变化。     

杂多酸引发四氢呋喃开环聚合反应Ⅶ.以氧杂环丁烷为促进剂

在以低浓度杂多酸(HPA)催化四氢呋喃(THF)聚合反应中,我们曾采用环氧乙烷(EO)、环氧丙烷(PO)和环氧氯丙烷(ECH)等三元环醚为促进剂,发现它们对聚合反应都具有很好的促进效果[1～3]. 本文进一步研究了具有四元环醚结构的氧杂环丁烷(OX)对THF聚合的促进效果.     

CH3COSbCl6催化四氢呋喃聚合的研究

ＣＨ_３ＣＯＳｂＣｌ_６催化四氢呋喃聚合的研究栗方星，王红军，马克勤（南开大学化学系，天津，３０００７１）关键词聚四氢呋喃，乙酰基六氯锑酸盐，表观聚合反应速率常数，五氯化锑ＴＨＦ聚合为平衡聚合反应应［１，２］，文献报道［３，４］Ｅｔ３ＯＢＦ４、Ｅｔ３Ｏ...     

单茂钛催化剂用于苯乙烯-乙烯嵌段共聚物的合成与表征

乙烯（Ｅ）与苯乙烯（Ｓ）的嵌段共聚合用自制的两种催化剂———茂基三呋喃甲氧基钛［ＣｐＴｉ（ＯＣＨ２Ｏ）３］和茂基三苄氧基钛［ＣｐＴｉ（ＯＣＨ２Ｐｈ）３］进行了研究．考察了促进剂三甲基铝（ＴＭＡ）及乙烯的预聚合时间对聚合结果的影响，发现不同的催化体系有不同的［ＴＭＡ］最佳值以及随着乙烯预聚合时间的延长总的催化效率降低．对嵌段共聚合产物用丁酮、四氢呋喃和氯仿连续萃取分离，得到四氢呋喃中的可溶级分即嵌段共聚物ＰＥ ｂ ｓＰＳ，它占总嵌段共聚合产物的４０ｗｔ％～６０ｗｔ％．对嵌段共聚物用ＤＳＣ、ＷＡＸＤ、ＦＴＩＲ和１３Ｃ ＮＭＲ等方法进行了表征．     

杂多酸引发四氢呋喃聚合反应 Ⅲ.环氧乙烷对聚合反应的影响

最近我们研究发现环氧乙烷（ＥＯ）可有效地促进低腐蚀性磷钨杂多酸（ＰＷ１２）引发的四氢呋喃（ＴＨＦ）聚合反应,产物分子量可通过体系中水或低分子二醇的含量进行控制［１,２］．而在没有ＥＯ存在时,相似条件下ＰＷ１２引发ＴＨＦ聚合反应２４ｈ,没有检出聚合物［...     

四氢呋喃开环均聚以及四氢呋喃和环硫氯丙烷共聚新催化体系

研究发现无水稀土氯化物 ５０％发烟硫酸体系是四氢呋喃（ＴＨＦ）均聚和四氢呋喃与环硫氯丙烷（ＣＭＴ）共聚合的优良新催化体系．考察了ＴＨＦ均聚反应特征，在合适条件下，ＴＨＦ聚合以６５％转化率制得粘均分子量达１０，０００～１５，０００的白色聚四氢呋喃（ＰＴＨＦ）固体．端羟基分析法测得聚合物的分子链两端均为羟基．考察了影响ＴＨＦ ＣＭＴ共聚合反应诸因素，如聚合温度和时间、两单体的比例等，制得数均分子量为１，０００左右的淡黄色粘性固体共聚物．     

四氢呋喃与环氧氯丙烷共聚合的研究

<正> 晃玉等曾以BF_3-二元醇(DO)引发四氢呋喃(THF)与环氧氯丙烷(ECH)共聚合,用所得共聚醚制成嵌段聚醚聚氨酯,与用THF均聚醚或THF-环氧丙烷(PO)共聚醚为软段的聚氨酯相比,分别在低温性能及强度上有明显改进.且由于引入氯甲基侧基可作进一步接枝共聚改性。但用BF_3-DO为引发剂很难制得不含环聚体的共聚醚,     

杂多酸引发四氢呋喃聚合反应 Ⅱ.水的反应行为

前报我们对低腐蚀性非均相的磷钨杂多酸Ｈ３ＰＷ１２Ｏ４０（ＰＷ１２）引发体系进行了研究［１］,发现环氧乙烷（ＥＯ）可有效地促进ＰＷ１２引发的四氢呋喃（ＴＨＦ）聚合反应,大幅度地降低了引发剂用量,聚合物收率显著提高,并发现聚合过程中不存在链终止反应．产物...     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Catalyst free,visible-light promoted photoaddition reactions between C60 and N-trimethylsilylmethyl-substituted tertiary amines for synthesis of aminomethyl-1,2-dihydrofullerenes

An efficient and benign method for the preparation of aminomethyl-substituted fullerenes has been developed. The process, involving catalyst free, visible-light irradiation of 10% EtOH-toluene solutions containing fullerene C₆₀ and N-trimethylsilylmethyl-substituted amines by using a 20 W compact fluorescent lamp, leads to formation of aminomethyl-substituted fullerene adducts in a highly efficient manner. The photoaddition reaction takes place via a pathway initiated by visible light absorption by C₆₀, followed by SET from the amine to the triplet excited state of C₆₀. Ethanol-promoted desilylation of the resulting a minimum radical then generates the corresponding α-amino radical which couples with the C₆₀ radical anion to form the anion precursor of the fullerene adducts. The new approach using visible-light takes place under mild conditions and it does not require the use of photocatalysts. Thus, the method developed in this effort could broadens the range of functionalized fullerene derivatives that can be readily prepared.     

Highly efficient and stereoselective cycloaddition of nitrones to indolyl- and pyrrolylacrylates

The reactions of various nitrones with indolyl- and pyrrolylacrylates proceeds regioselectively with high diastereoselectivity in the case of aldonitrones, and represents an effective method for obtaining new indolyl- and pyrrolyl-substituted isoxazolidine carboxylates stabilized by weak (CH?O) and moderate (NH?N) strength intramolecular hydrogen bonding. The resulting cycloadducts exhibit promising in vitro anti-influenza activities.     

Transition metal-free direct amination of benzoxazoles using formamides as nitrogen sources

A transition metal-free method for the direct amination of benzoxazoles using formamides as nitrogen sources is reported, which was mediated by an inexpensive and environmentally friendly tetrabutylammonium iodide/tert-butyl hydroperoxide system and gave the 2-aminobenzoxazole derivatives with moderate to good yields.     

l-Proline-catalyzed five-component domino reaction leading to multifunctionalized 1,2,3,4-tetrahydropyridines

Multifunctionalized 1,2,3,4-tetrahydropyridines are concisely synthesized in good yields via l-proline-catalyzed or l-proline/FeCl₃-cocatalyzed one-pot multicomponent reactions (MCRs). The MCRs involve a domino hydroamination/prins reaction/Mannich-type reaction/intramolecular dehydration-cyclization process. The molecular structure of 5baa, one of multifunctionalized 1,2,3,4-tetrahydropyridines, was confirmed by single-crystal X-ray diffraction.     

Exploring the scope of the Gewald reaction: Expansion to a four-component process

An efficient four-component reaction was developed to take advantage of the reactivity of the 2-aminothiophene-3-carbonitrile functionality, which is obtained during the classical three-component Gewald reaction. Various α-methylene bearing ketones were reacted with malononitrile, elemental sulfur, and aryl/heteroarylnitrile derivatives in t-BuOH/NaOH to afford 2-arylthieno[2,3-d]pyrimidin-4-amines in high yields. Preliminary studies revealed the photophysical properties of the products and their potential for use as metal sensors.