钨硅酸的制备及其在催化合成缩酮(醛)中的应用

本文探讨了钨硅酸的制备方法，以合成环己酮1，2-内二醇缩酮为例验证钨硅酸的催化活性，并探讨了合成其它缩酮（醛）的适宜条件，得到的收率分别为：环己酮1，2-丙二醇缩酮85．5％、环己酮乙二醇缩酮89．6％、丁酮乙二醇缩酮79．5％、丁醛乙二醇缩醛89．1％、丁醛1，2丙二醇缩醛81．5％。     

以高分子为载体的Lewis酸催化剂——苯乙烯、甲基丙烯酸甲酯共聚物-四氯化钛复合物的制备及其在有机合成中的应用

均相催化剂的固载化和以高分子材料作为催化剂载体的研究及开发,近年来受到人们的的重视。Neckers和Sket等曾将极易水解的AlCl_3和BF_3分别与聚苯乙烯反应制成高分子载体催化剂,应用于缩醛、缩酮、酯化等反应,具有良好的催化效能。本文将在空气中极易水解的Lewis酸四氯化钛与苯乙烯和甲基丙烯酸甲酯的共聚物小球反应,制成了一种十分稳定的高分子载体Lewis酸催化剂,证明它对酯化、缩醛、缩酮等反应有较高的催化活性,并可重复使用、回收再生。由于它制备简单、操作方便、易于从反应体系中分离、无污染,因此具有良好的应用前景。     

硅胶固载化—（Lewis）酸催化剂的研究：Ⅰ.硅胶固载化—四氯化钛复合物催…

以硅胶球为基质键合ｒ－ＧＯＰＳ并各接枝上具有络合功能的三种配件，邻位氨基吡啶、间酰氨基吡啶及对酰氨基吡啶，再和ＴｉＣｌ４络合成固载化的Ｌｅｗｉｓ酸催化剂，将这些催化剂进行缩醛、缩酮及酯化反应，有很好的催化活性，重复使用多次不失效。本文在合成此类催化剂的过程中利用热失重（ＴＧ）法及等离子光谱法（ＩＣＰ）等检测方法对合成此类催化剂的第一步进行跟踪检测，得到键合反应，开环反应及络合反应过程中的键合量，开     

脱铝超稳Y沸催化合成缩醛(酮)

缩醛 (酮 )类化合物是近十几年来发展起来的新型香料化合物 ,具有优于母体醛 (酮 )的花香 ,留香持久 ,香气类型多 ,化学性质稳定等特点 .缩醛(酮 )也常用于有机合成的羰基保护或反应中间体 ,有时也用作反应溶剂 .缩醛 (酮 )合成反应的常用催化剂为无机酸 (如 H2 SO4 、HCl、H3PO4等 ) ,但副反应多 ,腐蚀性强和易污染环境等缺点 ,使其使用受到限制 .近年来的研究表明 ,一些固体酸、Sn Cl4 [1] 、Fe Cl3[2 ] 、铌酸[3] 、Ce4 离子交换的蒙脱土 [4 ]等对缩醛 (酮 )反应有良好的催化作用 ,而且使后处理工艺简化 .分子筛作为催化剂由于其…     

高分子固载化Lewis酸催化剂——聚苯乙烯-三氯化铝/四氯化钛复合物

<正> 均相催化剂的固载化是目前催化剂研究方向之一。Skct等首次将BF_5和AlCl_3分别与苯乙烯反应制成高分子催化剂,对酯化、缩醛、缩酮等有机反应具有良好的催化作用。我们曾将四氯化钛与聚苯乙烯反应制成一种稳定复合物,有良好的催化效能。为了改进其重复使用性能,本文将等摩尔的AlCl_3,和TiCl_4的Lewis酸同时与聚苯乙烯交     

硅胶固载化─（Lewis）酸催化剂的研究Ⅰ．硅胶固载化─四氯化钛复合物催化体系

以硅胶球为基质键合γ－ＧＯＰＳ并各接枝上具有络合功能的三种配体，邻位氨基吡啶、间酰氨基吡啶及对酰氨基吡啶，再和ＴｉＣｌ＿４络合成固载化的Ｌｅｗｉｓ酸催化剂，将这些催化剂进行缩醛、缩酮及酯化反应，有很好的催化活性，重复使用多次不失效．本文在合成此类催化剂的过程中利用热失重（ＴＧ）法及等离子光谱法（ＩＣＰ）等检测方法对合成此类催化剂的每一步进行跟踪检测，得到键合反应，开环反应及络合反应过程中的键合量，开环相量和ＴｉＣｌ＿４络合量的定量数据．对固载化催化剂表面的接枝量有所了解，从而可进一步检测此类催化剂的催化效应并得到一些启示．     

固体酸催化合成邻苯二甲酸二戊酯的研究

以苯酐和正戊醇为原料,采用自制的固体酸SO4^2-／SiO2、SO4^2-／Fe2O3、SO4^2-／SnO2及SO4^2-／TiO2作为催化剂合成邻苯二甲酸二戊酯（DAP）,分别考察固体酸催化剂的种类、固体酸催化剂的用量、醇酐比、反应时间等因素对合成DAP产率的影响。实验结果表明,其优化的工艺操作条件为：苯酐0．1mol,固体酸催化剂SO4^2-／SiO2 1．7g,醇酐比2．4：1,带水剂二甲苯20mL,反应时间3．5h,其产品收率达91．3％以上。SO4^2-／SnO2作为该反应的催化剂具有催化活性高、寿命长、可多次重复使用、产物易纯化分离且产品色泽浅等优点,可望代替传统的浓硫酸作催化剂应用于DAP的合成。     

高岭土负载SO42-/ZrO2-TiO2催化剂的制备及其在缩酮合成中的应用

以经H2SO4处理焙烧的高岭土为载体,制备了以其负载的SO2-4/ZrO2-TiO2固体酸催化剂。 用FT-IR、XRD和NH3-TPD等测试技术表征了催化剂的微观结构及酸强度,考察了对环己酮乙二醇缩酮反应的催化活性及稳定性。 结果表明,酸化处理使高岭土表面酸量增加,但酸强度变化不大,而其负载SO2-4/ZrO2-TiO2后,经500 ℃焙烧3 h其酸量及酸强度显著升高。 环己酮用量为0.2 mol、乙二醇0.24 mol、催化剂1.2 g、带水剂环己烷15 mL,回流反应70 min后,缩酮收率可达96.8%,催化剂重复使用5次收率保持在90%以上。     

高岭土负载SO2-4/ZrO2-TiO2催化剂的制备及其在缩酮合成中的应用

以经H2SO4处理焙烧的高岭土为载体,制备了以其负载的SO4(2-)/ZrO2-TiO2固体酸催化剂.用FT-IR、XRD和NH3-TPD等测试技术表征了催化剂的微观结构及酸强度,考察了对环己酮乙二醇缩酮反应的催化活性及稳定性.结果表明,酸化处理使高岭土表面酸量增加,但酸强度变化不大,而其负载SO4(2-)/ZrO2-TiO2后,经500℃焙烧3 h其酸量及酸强度显著升高.环己酮用量为0.2 mol、乙二醇0.24 mol、催化剂1.2 g、带水剂环己烷15 mL,回流反应70 min后,缩酮收率可达96.8%,催化剂重复使用5次收率保持在90%以上.     

碘掺杂聚苯胺催化合成环己酮1,2-丙二醇缩酮

合成了聚苯胺-碘(PAn-I2)催化剂,并对其结构进行了表征。并通过环己酮与1,2-丙二醇合成环己酮1,2-丙二醇缩酮,探讨了PAn-I2对缩酮反应的催化活性。实验结果表明,PAn-I2是缩酮反应的良好催化剂,在环己酮100 mmol,n(环己酮)∶n(1,2-丙二醇)=1∶1.5,催化剂用量为反应物总质量的3%,环己烷12 mL,反应时间2 h的优化条件下,环己酮1,2-丙二醇缩酮的收率可达92.1%。     

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.