铁系固体酸催化剂的制备及催化合成水杨酸酯

制备了铁系固体酸催化剂(Ⅰ)并将其用于催化合成水杨酸酯，优化了反应条件：当Ⅰ用量为投料质量的6．1％，mol酸：mol醇=1：4，适当提高反应温度，合成水杨酸戊酯的反应时间可缩短至3h，产率达91．3％。合成其它水杨酸酯时也取得很高的产率。通过对比，Ⅰ的催化酯化能力优于Fe2O3／SO4^2-固体超强酸催化剂，套用6次后催化性能基本保持不变。     

固体超强酸SO4^2—／TiO2 催化合成异戊酸异戊酯

异戊酸异戊酯是ＧＢ2 760 - 86规定为允许使用的食用香料 ,也可微量用于化妆品、皂用香精中[1] 。异戊酸异戊酯传统合成方法为硫酸催化下由异戊酸与异戊醇直接酯化反应制得[2 ] ,由于浓硫酸易使有机物炭化、氧化 ,故副反应多、酯产物色泽深、产率受影响的诸多缺点 ,因此 ,有人开发了由异戊醇一步法合成异戊酸异戊酯的方法[3～ 5] ,但异戊酸异戊酯的收率不高 ,仅为 5 8～70 .6%。本文采用更换酯化反应催化剂的方法 ,以ＳＯ2 -4 ＴｉＯ2 固体超强酸作为催化剂 ,对异戊酸异戊酯的合成进行了研究。1　实验1 1　ＳＯ2 -4 ＴｉＯ2 固体超强酸的制…     

固体超强酸SO2-4/TiO2催化合成异戊酸异戊酯

异戊酸异戊酯是GB2760-86规定为允许使用的食用香料,也可微量用于化妆品、皂用香精中[1].异戊酸异戊酯传统合成方法为硫酸催化下由异戊酸与异戊醇直接酯化反应制得[2],由于浓硫酸易使有机物炭化、氧化,故副反应多、酯产物色泽深、产率受影响的诸多缺点,因此,有人开发了由异戊醇一步法合成异戊酸异戊酯的方法[3～5],但异戊酸异戊酯的收率不高,仅为58～70.6%.本文采用更换酯化反应催化剂的方法,以SO2-4/TiO2固体超强酸作为催化剂,对异戊酸异戊酯的合成进行了研究.     

稀土固体超强酸SO24-/TiO2/La3+催化合成水杨酸异丁酯

研究了以稀土固体超强酸SO24-/TiO2/La3+为催化剂,水杨酸和异丁醇为原料合成水杨酸异丁酯,并考察了影响反应的因素.结果表明,醇酸比为3:1,催化剂用量为1.0 g(水杨酸为0.1 mol的情况下),带水剂苯为15 mL,反应时间为3.0 h是最适宜的反应条件,酯化率达96.2%.     

稀土固体超强酸SO_4~(2-)/TiO_2/La~(3 )催化合成水杨酸异丁酯

研究了以稀土固体超强酸SO_4~(2-)/TiO_2/La~(3 )为催化剂,水杨酸和异丁醇为原料合成水杨酸异丁酯,并考察了影响反应的因素。结果表明,醇酸比为3:1,催化剂用量为1.0g(水杨酸为0.1mol的情况下),带水剂苯为15mL,反应时间为3.0h是最适宜的反应条件,酯化率达96.2％。     

树脂D732负载磷钨酸催化合成水杨酸酯

在水杨酸和正丁醇反应中,采用强酸性阳离子树脂D732负载磷钨酸为催化剂,合成了水杨酸酯。考察了醇/酸的摩尔比、反应时间、反应温度、催化剂的用量和催化剂的重复使用性等因素对反应酯化率的影响。结果表明,在反应温度为110℃,反应时间3h,酸/醇摩尔比为1:3,催化剂质量占水杨酸总质量的20%的较优条件下,酯化率达93.2%。催化剂不经处理重复使用4次,酯化率均在83%以上。依据该较佳的工艺条件,进一步催化合成其它水杨酸酯,酯化率均超过82%,表明D732负载磷钨酸具有良好催化效果。     

相转移催化合成乙酸异戊酯

乙酸异戊酯是无色透明液体,具有香蕉和梨的香味,可用作食用香精,也是很好的有机溶剂,广泛用于医药、涂料、印染行业。合成乙酸异戊酯的经典方法是用浓Ｈ２ＳＯ４为催化剂酯化制得,但由于硫酸严重腐蚀设备和易引起副反应,使产品纯度低,后处理过程复杂,因而促使人们研究其它合成方法。自１９８１年黄化民等报道用无机硫酸盐作催化剂以来,不少研究者采用了用不同的无机盐超强酸、固体酸、杂多酸、离子交换树脂作为催化剂进行了广泛研究。但这些催化剂也有其自身的缺点。以季铵盐作为乙酸异戊酯的酯化反应催化剂尚未见文献报道,笔者采…     

稀土固体超强酸SO~4^2^-/TiO~2/La^3^+催化合成水杨酸 异丁酯

研究了以稀土固体超强酸SO~4^2^-/TiO~2/La^3^+为催化剂,水杨酸和异丁醇为原料合成水杨酸异丁酯,并考察了影响反应的因素。结果表明,醇酸比为3:1,催化剂用量为1.0g(水杨酸为0.1mol的情况下),带水剂苯为15mL,反应时间为3.0h是最适宜的反应条件,酯化率达96.2%。     

两个简单的酯化反应实验

教学中以乙酸异戊酯的合成作为课堂演示实验有如下优点：酯化装置操作简单、需时少、成功率高;反应物之一异戊醇气味奇臭,而产物乙酸异戊酯则具有比乙酸乙酯更加浓郁的水果香味,反应前后这2种气味形成强烈的对比,使实验现象更加鲜明、生动有趣,从而更有利于激发学生的学习兴趣和活跃课堂气氛,可以避兔现行课本中酯化演示实验和学生实验简单的重复。使学生做乙酸乙醋的实验时有一种新鲜感,自然地产生一种“看看我做的这种醋是否也那么香”的求知欲。     

“乙酰水杨酸的制备和分析表征”教学实验的优化和改进

以水杨酸和乙酸酐为原料,硅胶为催化剂,利用微波技术优化改进“乙酰水杨酸的制备和分析表征”大学有机化学教学实验,通过实验探究,分析了微波功率、反应时间、原料配比等因素对最终产率的影响,得到了最佳实验条件：硅胶目数为100–200目,用量为0.25 g,反应时间60 s,反应温度70°C,微波功率500 W,乙酸酐与水杨酸的物质的量之比为2:1,平均产率约为68.0%。与常规加热情况下乙酰水杨酸的制备相比,微波辅助合成法具有操作简便、反应时间短、产品的产率高、杂质少、对环境友好等优势。将该微波实验引入大学本科生有机化学实验教学,能开阔学生视野、丰富实验教学内容,进一步提高教学水平。     

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.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

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.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

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.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

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.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.