氧化钙在催化Aldol反应中的应用

以氧化钙(CaO)为催化剂,研究其在苯甲醛及苯乙酮Aldol羟醛缩合中的应用,研究结果显示:在60℃下,当CaO的用量为20%时,该Aldol反应的产率达到最大值,为80%;此外,研究发现苯甲醛上取代基的种类会对产率有较大影响,当苯甲醛上连接较强的吸电子基团时会使反应速率加快,同时也会产生较多的副产物,而弱的吸电子基团可以使产率大幅度提高;氧化钙作为催化剂,其Ca~(2+)和O~(2—)可以活化羰基,进而加速反应。     

纤维素酶催化Aldol反应的研究

研究了纤维素酶在有机介质中多功能性催化芳香醛和丙酮的Aldol反应。考察了不同酶源对催化Aldol反应的影响,筛选出Cellulase from Trichoderma viride在DMSO中催化芳香醛和丙酮的Aldol反应的活性最高,与无酶空白对照实验和失活的Cellulase from Trichoderma viride的催化实验做了比较,未检测到产物的生成,确定纤维素酶可以催化苯甲醛和丙酮的Aldol反应。优化了反应溶剂、体系含水量、反应温度和酶浓度的工艺参数,在50℃,体系含水量为15%,酶浓度为10 mg·mL-1,在恒温振荡器中反应24 h,苯甲醛和丙酮的Aldol反应收率能达到85%。研究了各类的取代芳香醛与丙酮的Aldol反应情况,发现纤维素酶对于Aldol反应有着较强的底物适应性。同时提出了纤维素酶催化芳香醛和丙酮的Aldol反应的可能机理。     

L-脯氨酰胺在不对称Aldol反应中催化应用研究进展

Aldol反应是构建C-C键最有效的有机合成方法之一,不对称Aldol反应产物是合成多种复杂有机化合物的重要原料或关键中间体。L-脯氨酰胺是催化不对称Aldol反应的重要手性催化剂之一,具有结构多样、合成简洁、立体选择性高等优点,近年来被广泛地研究。对近年来L-脯氨酰胺类手性催化剂在不对称Aldol反应中的催化应用进行综述。     

水相中β-CD固载脯氨酸催化Aldol反应

将L-脯氨酸固载于β-环糊精（β-CD）上,以合成的环糊精包合物为催化剂,来催化一系列的不对称Aldol反应。单纯使用β-环糊精催化Aldol反应作空白实验,没有任何进展,使用15％（mol）的固载催化剂,得到了满意的结果。催化剂通过简单的过滤回收,不需要作任何修饰再生,循环7次实验后催化剂的活性没有明显降低,起到了长效催化的功能。     

离子液体在Aldol反应中的应用

综述了离子液体在羟醛缩合(Aldol)反应中的应用。离子液体不仅可以提高反应收率,而且通过选择离子液体/催化剂体系,可以定向的得到预期的Aldol产物。     

催化精馏技术在酯化反应中的应用

催化精馏技术应用于酯化反应体系,提高了反应的转化率,原材料利用率和产品收率。与传统工艺相比,具有生产流程简单、能耗低,设备投资和操作费用低、无环境污染等优点。催化精馏技术应用于酯化行业生产,对提高酯化行业的技术水平和经济效益具有积极意义。     

疏水改性氧化钙催化制备生物柴油的研究

以溴化苄作为改性剂,采用化学键合方法对市售氧化钙进行表面改性,考察改性氧化钙固体碱催化菜籽油-甲醇酯交换反应制备生物柴油的性能,并在此基础上对该催化体系的耐水性进行考察。通过对反应体系中醇/油摩尔比、催化剂用量和反应时间进行优化,最终得出在醇/油摩尔比为15∶1,催化剂用量为5%以及表面改性剂溴化苄用量为0.2%时,表面改性氧化钙上生物柴油产率在反应3h即可达到99.8%,而未改性氧化钙为催化剂时在相同反应条件下生物柴油产率仅为35.3%。     

氧化钙催化活性在焦油裂解过程中的变化规律

在以循环床锅炉循环灰为热载体、部分气化产生的半焦为锅炉燃料的煤的部分气化技术中,循环灰中的氧化钙对降低焦油产率、提高煤气产率是有利的。以焦油中的苯和甲苯为对象,用固定床反应器实验研究了焦油裂解过程中反应对氧化钙催化活性的影响,测定了失活系数,探讨了失活机理。实验结果表明,随着积碳量的增加,氧化钙颗粒的比表面积和空隙率减小,裂解反应速率下降,裂解产物中碳的总产率增加。     

氧化钙催化菜籽油酯交换制备生物柴油

以菜籽油和甲醇为原料,在固体碱催化剂的作用下,通过酯交换反应制得生物柴油(脂肪酸甲酯)。以氧化钙为催化剂,通过正交试验得到该反应的最佳工艺条件:温度60℃,催化剂用量为菜籽油质量的1%,醇油比为10∶1(物质的量比),反应时间3 h,甘油收率达80.8%。     

双功能磺酰胺的合成及不对称催化羟醛缩合反应研究

合成了一系列单磺酰化手性二胺,并用于催化丙酮与对硝基苯甲醛的不对称羟醛缩合反应。研究了手性二胺以及磺酰基结构对反应的影响,也研究了添加剂对反应的影响。对催化剂进行筛选,发现对硝基苯磺酰基取代的(1 S,2 S)-1,2-二苯基乙二胺为最佳催化剂,采用苯甲酸作为添加剂,反应可取得中等收率与对映选择性。     

Tandem Catalysis by Lipase in a Vinyl Acetate‐Mediated Cross‐Aldol Reaction

The lipase Novozym435 (0.6% w/w) was used in tandem with organocatalysts in a first vinyl/isopropenyl acetate‐mediated aldol reaction. The reaction was facilitated through the lipase‐catalyzed in situ generation of acetaldehyde/acetone. The important features of the present methodology include the mild and facile reaction conditions, regenerability of the lipase, comparatively high yields and minimal side product formation.     

Chymopapain‐Catalyzed Direct Asymmetric Aldol Reaction

Chymopapain, a cysteine proteinase isolated from the latex of the unripe fruits of Carica papaya, displays a promiscuous activity to catalyze the direct asymmetric aldol reactions of aromatic and heteroaromatic aldehydes with cyclic and acyclic ketones in acetonitrile in the presence of a phosphate buffer. The excellent enantioselectivities of up to 96% ee and high diastereoselectivities of up to >99:1 (anti/syn) were achieved. The novel catalytic promiscuity of chymopapain widens the applicability of this biocatalyst in organic synthesis.     

Combination of Enantioselective Metal Catalysis and Organocatalysis: Enantioselective Sequential Hydroformylation/ Aldol Reactions

This work reports the possibility of controlling the sense of enantio‐ and diastereoinductions in the sequential hydroformylation and aldol reactions via the judicious combination of a chiral metal catalyst with a chiral organocatalyst. The diastereoselectivity of the reaction between styrene, syngas and acetone can be increased by using a matched pair of catalysts, [rhodium/(2S,4S)‐Chiraphite]/(S)‐organocatalyst and decreased, but not inverted, by using a mismatched pair of catalysts, [rhodium/(2R,4R)‐Chiraphite]/(S)‐organocatalyst.     

复原镁铝水滑石固体碱在Aldol反应中的应用

以镁铝水滑石为前体焙烧制得镁铝复合氧化物,在含水体系中水合催化取代苯甲醛和丙酮的aldol反应。结果显示,水滑石前体经过复原处理后活性高于普通Mg/Al水滑石;Mg/Al比为4∶1,NaOH/Na2CO3为沉淀剂,镁铝的硝酸盐作为金属盐来源制备的催化剂对对硝基苯甲醛和丙酮之间的aldol反应具有最好的催化效果。     

New Simple Hydrophobic Proline Derivatives as Highly Active and Stereoselective Catalysts for the Direct Asymmetric Aldol Reaction in Aqueous Medium

New 4‐substituted acyloxyproline derivatives with different hydrophobic properties of the acyl group were easily synthesized and used as catalysts in the direct asymmetric aldol reaction between cyclic ketones (cyclohexanone and cyclopentanone) and several substituted benzaldehydes. Reactions were carried out using water, this being the best reaction medium examined. Screening of these catalysts showed that compounds bearing the most hydrophobic acyl chains [4‐phenylbutanoate and 4‐(pyren‐1‐yl)butanoate] provided better results. The latter catalysts were successfully used in only 2 mol% at room temperature without additives to give aldol products in excellent stereoselectivities. These results demonstrate that derivatization of the proline moiety with the proper simple hydrophobic substituent in the 4‐position can furnish highly active and stereoselective catalysts without the need of additional chiral backbones in the molecule. Finally, an explanation of the observed stereoselectivities in the presence of water is provided.     

Proline‐Catalyzed Asymmetric Aldol Reaction in Guanidine‐ Derived Ionic Liquids

A remarkable improvement of both the chemical yield (from 6% to 82%) and the enantiomeric excess (up to >99%), of (S)‐proline catalyzed direct aldol reactions of a wide range of aldehydes with acetone was found when hexasubstituted or pentasubstituted guanidinium salts were added as ionic liquids. Effects of temperature, amount of proline and the type of guandidinium salts on the outcome of the reaction were investigated.     

Asymmetric Aldol Reaction Using Immobilized Proline on Mesoporous Support

The aldol reaction of hydroxyacetone with different aldehydes using immobilized proline on a mesoporous support, assisted by heat and microwaves, has been explored. It was found that heterogenized L ‐proline on MCM‐41 catalyzed aldol reactions in both hydrophilic and hydrophobic solvents, and provided stereoselectivities in some cases complementary to the homogeneous catalyst. The heterogeneous catalysts could be reused without significant lost of stereoselectivity.     

Asymmetric Aldol Reaction of Dichloroacetaldehyde Catalyzed by Diarylprolinol

The asymmetric cross‐aldol reaction of dichloroacetaldehyde with aldehyde pronucleophiles proceeds in the presence of a trifluoromethyl‐substituted diarylprolinol to afford γ,γ‐dichloro‐β‐hydroxy aldehydes in good yield with excellent enantioselectivity. The obtained products are useful synthetic intermediates; they were successfully converted to form chiral alkynes and dichloroalkenes.

     

An Organocatalytic Domino Thia‐Michael/Aldol Condensation Reaction: Highly Enantioselective Synthesis of Functionalized Dihydrothiophenes

An organocatalytic domino thia‐Michael/aldol condensation reaction of α, β‐unsaturated aldehydes with 1, 4‐dithiane‐2,5‐diol catalyzed by chiral diphenylprolinol TMS ether has been developed, which provides a new practical and direct route to chiral dihydrothiophenes with high yields (up to 90%) and excellent enantioselectivities (up to>99% ee). The catalytic mechanism of the domino reaction was further confirmed through the APCI‐MS detection of proposed reaction intermediates.