Imidazoles: Effective Catalysts for Baylis-Hillman Reaction in Aqueous Media

β-Substituted enones have been considered less reactive in Baylis-Hillman reaction. The reaction of cyclic enones is sluggish or does not occur at all under traditional conditions. Various catalysts have been developed to pro mote the reaction of cyclic enones but with limited success. In previous study, we found that imidazole can catalyze the Baylis-Hillman reaction involving cyclic enones in aqueous THF solution.[1] In our continued efforts, we screened a variety of imidazoles to develop superior catalyst, and we found that the reaction could be greatly accelerated by adjusting the pH value of the water solution.     

Azoles: Effective Catalysts for Baylis-Hillman Reaction in Aqueous Media

β-Substituted enones have been considered less reactive in Baylis-Hillman reaction. The reaction of cyclic enones is sluggish or does not occur at all under traditional conditions. Various catalysts have been developed to pro mote the reaction of cyclic enones but with limited success. In previous study, we found that imidazole can catalyze the Baylis-Hillman reaction involving cyclic enones in aqueous THF solution. [1] In our continued efforts, a variety of azole compounds were examined in Baylis-Hillman reaction. We found that the azoles act as effective catalysts in properly adjusted water solution.     

The Aqueous Trimethylamine Mediated Baylis-Hillman Reaction

Aqueous trimethylamine mediated Baylis-Hillman coupling of alkyl acrylates with aldehydes is described.     

Intramolecular Baylis-Hillman Reaction: A Pathway to Substituted Coumarins

The acrylate ester of salicylaldehyde, in the presence of DABCO, affords a crystalline coumarin salt. Formation of this derivative confirms a vital intermediate in the mechanism of the reaction. Salicylaldehyde, suitably protected, reacts with methyl acrylate to afford a novel coumarin not unlike the vasodilator chromonar.     

水相钯催化Suzuki反应

钯催化的Suzuki反应是构建Csp2—Csp2键的主要方法之一,已广泛应用于医药、天然产物及先进功能材料等联芳类化合物的合成.近年来,水相Suzuki反应引起了人们的高度关注.对以纯水及水/有机混溶剂为介质的水相Suzuki反应的研究进展作一综述,特别是围绕如何解决水相Suzuki反应活性的问题,以催化体系为主线,重点介绍了水溶性配体/钯、表面活性剂、微波促进的非水溶性配体/钯及无配体钯等催化体系在水相Suzuki反应中的应用.     

水相Reformatsky反应研究进展

近30年来,在水介质中形成碳-碳键一直是有机合成的研究热点.本文综述了水相中Reformatsky反应的研究进展,并对反应机理和应用作了简要的阐述.     

膦催化的Baylis-Hillman反应

Baylis-Hillman反应是一类非常有应用前景的有机合成反应, 常用的催化剂包括胺类、有机膦等. 与胺类催化剂相比, 有机膦亲核性更强, 从该反应的反应机理来看有机膦是该反应更有效的催化剂. 综述了膦催化的Baylis-Hillman反应最新的研究进展.     

胺催化下的Baylis-Hillman反应

Baylis-Hillman (B-H)反应是在催化剂作用下由活泼烯烃和亲电试剂发生的偶合反应, 其产物是一个具有多官能团的化合物. 胺类催化剂是反应中应用最广泛的一类催化剂. 综述了各种胺催化下的Baylis-Hillman反应的研究进展.     

金属参与的水相烯丙基化反应

近30年来,水介质中碳-碳键的形成一直是研究的热点,其优越性也逐渐被人们所认知。在已发现的水相金属有机反应中,水相烯丙基化反应是研究得较多和较深入的反应之一。水相烯丙基化反应由于其发展速度较快,新的金属及金属体系参与的烯丙基化反应以及水相烯丙基化反应的机理研究不断被报道。本文综述了水相中金属参与烯丙基化反应的最新研究进展,并对新的反应机理作了简要的阐述。     

非传统介质中的Baylis-Hillman反应

Baylis-Hillman反应是一个为数不多的形成碳—碳键的原子经济反应, 因其产物富含官能团而成为非常有潜力的合成有机多功能分子的有力工具. 然而, 反应速度慢、反应产率低是该反应常遇到的问题. 为了克服这些缺点, 近年来, 许多新颖的溶剂被用于这个反应. 本文综述了这些方面的最新研究进展和发展趋势.     

不对称Baylis-Hillman反应研究进展

综述了光学活性的活化烯、亲电试剂、催化剂和溶剂对Baylis_Hillman反应的不对称诱导效果     

Asymmetric Catalytic Aziridination of Cyclic Enones

The first catalytic method for the asymmetric aziridination of cyclic enones is described. The presented organocatalytic strategy is based on the use of an easily available organocatalyst that is able to convert a wide range of cyclic enones into the desired aziridines with very high enantiomeric purity and good chemical yield. Such a method may very well open up new opportunities to stereoselectively prepare complex chiral molecules that possess an indane moiety, a framework that is found in a large number of bioactive and pharmaceutically important molecules     

Microwave Assisted Michael Addition of Cycloalkenones and Substituted Enones on the Surface of Alumina in Dry Media

The Michael addition of ethyl acetoacetate, acetyl acetone and ethyl cyanoacetate to cycloalkenones and β -substituted enones and enal has been accomplished efficiently on the surface of alumina under microwave irradiation in dry media.     

BINOL Phosphoric Acid‐Catalyzed Asymmetric Mannich Reaction of Cyclic N‐Acyl Ketimines with Cyclic Enones

A highly enantio‐ and diastereoselective Mannich reaction of cyclic N‐acyl ketimines generated in situ from 3‐hydroxyisoindolin‐1‐ones with cyclic enones has been accomplished using a chiral phosphoric acid catalyst to afford the chiral isoindalinone derivatives in high yields with excellent enantioselectivities (upto 97 % ee). This is the first report on the synthesis of chiral isoindolin‐1‐ones bearing adjacent quaternary and tertiary stereogenic centers.     

Chitosan-Based Magnetic Polymetallic Pd-Catalysts for Heck Reaction in Aqueous Media

Russian Journal of General Chemistry - A mechanochemical method was developed for the synthesis of ferromagnetic Pd–Fe–Co–Ni composites based on the natural biopolymer chitosan,...     

Henry Reaction in Aqueous Media：Chemoselective Addition of Aldehydes

The chemoselective addition of aldehydes in aquoues medium was obtained under mild condition using improved Henry reaction.     

水相中锌促进的羰基化合物频哪醇偶联反应实验设计

介绍水相中锌促进的羰基化合物频哪醇偶联反应的实验设计。通过苯甲醛频哪醇偶联反应得到相应的1,2-二苯基．1,2-乙二醇,学习水相有机反应和微量反应的基本操作,加强基础研究、绿色化学与有机化学实验之间的紧密联系。     

苯甲酰丙酮存在下含水体系中合成二茂钛取代水杨酸配合物

Four titanocene complexes were prepared in aqueous or two-phase medium by the reaction of benzoylacetone titanocene with substituted salicylic acid, respectively. Based on the UV-Vis spectra, we studied the accelerating effect of the benzoylacetone on the reaction rate quantificationally. The results demonstrated that the presence of it not only stabilizes the “Cp₂Ti” species and accordingly makes pH value of the aqueous solution of substituted salicylic acid increased but also prompts the reaction due to the presence of its conjugation structure and oleophyllic group. Furthermore, the presence of benzoylacetone is in favor of the simplification of the products.     

Reversal of Enantioselectivity in the Conjugate Addition Reaction of Cyclic Enones with the CuOTf/Azolium Catalytic System

Hydroxyamide-functionalized azolium salt (NHC•HI 4) was evaluated for dual enantioselective control in a Cu-catalyzed asymmetric conjugate addition (ACA) reaction. This investigation was based on our previously reported ACA reaction catalyzed using CuOTf combined with NHC•AgI complex 1. It was revealed that the stereocontrol of the catalytic ACA reaction depended on the order of the addition of the substrates. Additionally, the chiral NHC ligand precursors, substrates, the relationship between the catalyst ee (ee_cat) and product ee (ee_pro), and halogen counter anion were completely evaluated. These results suggested that the catalytic performance of the CuOTf/4 system was comparable with that of the CuOTf/1 system. Furthermore, to gain knowledge of the Cu species generated using CuOTf and NHC ligand precursor, the reaction of CuOTf with 1 was investigated. Although obtaining the corresponding NHC•CuX species failed, the corresponding NHC•AuCl complex 11 could be synthesized by allowing 1 to react with AuCl•SMe₂.     

金属锌促进羰基化合物水相嚬呐偶合反应

报道了一种简便、有效的水相噤呐偶合反应。在含有少量季铵盐或季磷盐的氯化铵水溶液中．用金属锌促进羰基化合物进行水相噘呐偶合反应，其中加入的少量季铵盐或季磷盐有助于显著提高反应产率，噘呐醇产率由53％提高到87％。但噘呐偶合反应的产率受羰基周围环境的立体位阻影响较大，在此条件下，金属锌可有效地促进芳香族醛化合物进行水相噘呐偶合反应，得到产率较高的噘呐醇，但非对映异构体选择性差，而脂肪族醛化合物得到的噘呐醇产率较低，在同样条件下，酮类化合物不能顺利进行噘呐偶合反应。