Impregnated copper on magnetite as catalyst for the O-arylation of phenols with aryl halides简

Nanoparticle Fe304 encapsulated CuO, as a heterogeneous catalyst, is a facile system for the synthesis of diaryl ethers by the cross-coupling reaction of various substituted aryl halides with various substituted phenols, which avoids using any type of expensive ligand and can be recovered from the reaction mixture by using a simple magnet. Moreover, this catalyst can be reused three times with high catalytic activity.     

Two Reaction Mechanisms via Iminium Ion Intermediates: The Different Reactivities of Diphenylprolinol Silyl Ether and Trifluoromethyl‐Substituted Diarylprolinol Silyl Ether

The reactions of α,β‐unsaturated aldehydes with cyclopentadiene in the presence of diarylprolinol silyl ethers as catalyst proceed via iminium cations as intermediates, and can be divided into two types; one involving a Michael‐type reaction (type A) and one involving a cycloaddition (type B). Diphenylprolinol silyl ethers and trifluoromethyl‐substituted diarylprolinol silyl ethers, which are widely used proline‐type organocatalysts, have been investigated in this study. As the LUMO of the iminium ion derived from trifluoromethyl‐substituted diarylprolinol silyl ether is lower in energy than that derived from diphenylprolinol silyl ether, as supported by ab initio calculations, the trifluoromethyl‐substituted catalyst is more reactive in a type B reaction. The iminium ion from an α,β‐unsaturated aldehyde is generated more quickly with diphenylprolinol silyl ether than with the trifluoromethyl‐substituted diarylprolinol silyl ether. When the generation of the iminium ion is the rate‐determining step, the diphenylprolinol silyl ether catalyst is the more reactive. Because acid accelerates the generation of iminium ions and reduces the generation of anionic nucleophiles in the Michael‐type reaction (type A), it is necessary to select the appropriate acid for specific reactions. In general, diphenylprolinol silyl ether is a superior catalyst for type A reactions, whereas the trifluoromethyl‐substituted diarylprolinol silyl ether catalyst is preferred for type B reactions.     

Copper/Guanidine‐Catalyzed Asymmetric Alkynylation of Isatins

The highly enantioselective alkynylation of isatins, catalyzed by a bifunctional guanidine/CuI catalyst under mild reaction conditions, is described. The reaction is broad in scope with respect to alkyl/aryl‐substituted terminal alkynes and substituted isatins, thus affording bioactive propargylic alcohols in excellent yields and enantioselectivities.     

Synthesis of new substituted cylopentenone derivatives via a one-pot three-component reaction between arylglyoxals,acetylacetone, and amines in aqueous media

An efficient one-pot method for the synthesis of new substituted cylopentenone derivatives is described via reaction of arylglyoxals and acetylacetone with aliphatic amines. This reaction was carried out in aqueous media in the absence of any catalyst or promoter to produce substituted cylopentenone in high yield.     

Xanthan Sulfuric Acid: An Efficient and Recyclable Solid Acid Catalyst for Pechmann Condensation

In this report, substituted coumarins are formed via Pechmann condensation using various substituted phenols and ethyl acetoacetates in the presence of xanthan sulfuric acid as a solid acid catalyst under solvent-free conditions. This method is very simple, cost-effective, and has shorter reaction times, and the catalyst could be reused.     

Synthesis of indenes by the palladium-catalyzed carboannulation of internal alkynes

[reaction: see text] A number of highly substituted indenes have been prepared in good yields by treating functionally substituted aryl halides with various internal alkynes in the presence of a palladium catalyst. The reaction is believed to proceed by regioselective arylpalladation of the alkyne and subsequent nucleophilic displacement of the palladium in the resulting vinylpalladium intermediate.     

腐植酸负载Pd/Ni双金属催化剂对Heck反应催化性能的研究

制备了腐植酸负载Pd/Ni双金属催化剂, 该催化剂能够成功催化溴苯与丙烯酸、苯乙烯等乙烯基化合物的Heck反应, 产率均在85%以上; 催化剂能够不同程度地重复使用, 在催化溴苯与丙烯酸反应中, 催化剂重复使用3次后仍可得到42.9%的产率, 而在催化溴苯与苯乙烯反应中, 催化剂重复使用7次后也可得到26.7%的产率; 并且对不同取代基芳基卤与丙烯酸的反应也有很好的催化活性.     

Platinum‐Catalyzed Multi‐Step Reaction of Propargyl Alcohols with N‐Heteroaromatics

N‐Methyl indole reacts with but‐2‐yn‐1‐ol in the presence of PtCl₂ in MeOH giving indole derivatives having a substituted 3‐oxobutyl group at the 3‐position in good yield. Under the reaction conditions, various substituted indoles and substituted propargyl alcohols are successfully involved in the reaction giving the corresponding addition products in good to moderate yields. The catalytic reaction can be further extended to N‐phenyl pyrrole. In the present multi‐step reaction, PtCl₂ likely plays dual roles: as the catalyst for the rearrangement of propargyl alcohols to the corresponding alkenyl ketones and as the catalyst for the addition of indoles to the alkenyl ketones. Experimental evidence is provided to support the proposed mechanism.     

Synthesis of Substituted (±)-3,4-Dihydrocoumarins Using H-Y Zeolite

Synthesis of substituted (±)-3,4 Dihydrocoumarins were prepared with the reaction between substituted cinnamic acid and phenol catalysed by ecofriendly solid-acid catalyst H-Y zeolite involving esterification followed by ring closure.     

Ag Loaded on SiO2 as an Efficient and Recyclable Heterogeneous Catalyst for the Synthesis of Chloro‐8‐substituted‐9H‐purines

Ag support on silica has been used as an effective heterogeneous catalyst for the facile synthesis of chloro‐8‐substituted‐9H‐purine derivatives via the one‐pot reaction of 6‐chloro‐pyrimidines and substituted acids. The title compounds were formed as excellent yields with short reaction time under eco‐friendly conditions. The prepared catalyst (Ag/SiO₂) can be reused for a number of times with insignificant loss in its activity. This route has the advantage of being a cost‐effective, readily available, easy workup procedure.     

Catalytic, asymmetric, "interrupted" Feist-Bénary reactions

Pyrimidine derivatives of the cinchona alkaloids function as excellent asymmetric catalysts for the "Interrupted" Feist-Bénary Reaction. This reaction produces highly substituted hydroxydihydrofurans from simple starting materials under mild conditions. The asymmetric reaction gives high enantioselectivities with unsubstituted bromoketones, and high enantio- and diastereoselectivities with substituted substrates. Mechanistic experiments suggest that the hydrobromide salt of the alkaloid derivative is the active catalyst for the reaction.     

General and regioselective synthesis of substituted pyrroles by metal-catalyzed or spontaneous cycloisomerization of (Z)-(2-en-4-ynyl)amines

A general and regioselective synthesis of substituted pyrroles 2 by cycloisomerization of readily available (Z)-(2-en-4-ynyl)amines 1 is reported. Spontaneous cycloisomerization leading to 2 occurred in the course of preparation of enynamines bearing a terminal triple bond or a triple bond substituted with a phenyl or a CH2OTHP group. When the triple bond was substituted with an alkyl or alkenyl group, enynamines were stable and could be converted into the corresponding pyrroles by metal catalysis. CuCl2 was found to be an excellent catalyst for cycloisomerization of substrates substituted at C-3, while PdX2 in conjunction with KX (X = Cl, I) turned out to be a superior catalyst for the reaction of enynamines unsubstituted at C-3.     

Baylis-Hillman Reaction Involving Substituted Cyclic Enones in Aqueous Media

β-Substituted enones have been considered less reactive in Baylis-Hillman reaction. The reaction of cyclicenones is sluggish or does not occur at all under traditional conditions. [1] Therefore, substituted cyclic enones havebeen less explored in Baylis-Hillman reaction due to the extremely low reactivity. In this communication, we reported Baylis-Hillman reaction of substituted cyclic enones using our previously developed conditions with imidazole as catalyst. The reaction proceeded smoothly in aqueous media affording the desired product with good yields and moderate diastereoselectivity.     

SYNTHESIS OF COUMARINS CATALYZED BY ECO-FRIENDLY W/ZrO2 SOLID ACID CATALYST

Synthesis of substituted coumarins via reactions of resorcinol and substituted resorcinol with ethyl acetoacetate and ethyl α-methylacetoacetate (Pechmann reaction) are reported, in which the production of environmentally harmful waste streams is minimized by the use of a novel solid acid catalyst.     

水相铜/十二烷基取代酰肼-吡啶-N-氧化物催化咪唑的N-芳基化

设计合成了5种新型烷基取代酰肼-吡啶-N-氧化物,并将其作为水相铜催化含氮杂环与芳香碘代物偶联反应的配体.实验结果表明,十二烷基取代酰肼-吡啶-N-氧化物的催化效果最佳.对影响反应的其它条件,如铜源、碱、反应时间和温度等条件进行了优化,建立了最佳反应条件:CuO(10%,摩尔分数),NaOH(1 mmol),TBAB(5%,摩尔分数),L5(20%,摩尔分数),于120℃反应12 h,无需惰性气体保护.在此条件下,芳香碘代物与咪唑偶联反应的产率为60%~92%.该方法的特点是以水作为反应溶剂,长链烷基取代酰肼-吡啶-N-氧化物同时起到了铜催化剂配体和相转移催化剂的作用.     

Impregnated copper or palladium–copper on magnetite as catalysts for the domino and stepwise Sonogashira-cyclization processes: a straightforward synthesis of benzo[b]furans and indoles

An impregnated copper on magnetite catalyst is a versatile system for different domino Sonogashira-cyclization processes between 2-iodophenol and different alkynes to give the corresponding substituted benzo[b]furans. The catalyst could be recovered ten times without losing its activity. The related process using 2-iodoaniline was, however, better catalyzed by mixed palladium–copper on magnetite giving exclusively, in this case, the products arising from the Sonogashira coupling. The cyclization to the corresponding substituted indoles could be easily and quantitatively performed by zinc bromide treatment. This catalyst avoids the use of any type of expensive and difficult to handle organic ligand, showing excellent yields, under mild reaction conditions. The catalyst is very easy to remove from the reaction medium, just by using a simple magnet.     

A Gold(I)‐Catalyzed Domino Coupling of Alcohols with Allenes Enables the Synthesis of Highly Substituted Indenes

The reaction of aryl‐substituted allenes with alcohols under gold catalysis led to highly substituted indenes in good yields, with low catalyst loading and under mild conditions. During this domino transformation, two C?C bonds are formed with water as the only byproduct.     

碳负载钯催化剂对Heck反应的催化性能

研究了钯碳催化剂对芳基卤和取代芳基卤与丙烯酸和苯乙烯的Heck芳基化反应的催化性能.结果表明:在反应温度为80℃、反应时间为8h、四丁基溴化铵(TBABr)作为溶剂和三丁胺作为碱的条件下,钯碳催化剂对不同取代芳基卤与丙烯酸和苯乙烯的Heck芳基化反应具有良好的催化性能,产物收率在80%以上.     

Straightforward synthesis of alpha,beta-unsaturated thioesters via ruthenium-catalyzed olefin cross-metathesis with thioacrylate

The cross-metathesis reaction of S-ethyl thioacrylate with a variety of olefins is effectively catalyzed by using a ruthenium benzylidene olefin metathesis catalyst. This reaction provides a convenient and versatile route to substituted alpha,beta-unsaturated thioesters, key building blocks in organic synthesis.     

N-烷基取代烯胺合成方法研究

本文研究了一种通用的N-烷基取代烯胺合成方法。着重探讨了反应物配比、催化剂用量、反应时间等条件对缩合反应的影响。在优化的工艺条件下,能获得纯度较好,收率较高的N-烷基取代烯胺。