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1.
Acid‐catalyzed tandem reactions with auto‐tandem catalysis are effective for simplifying organic synthesis. However, some of the reported reactions were established based on the use of well‐designed substrate with complex structure. In some cases, owing to the existence of a big gap between each catalytic cycle, it is hard to bind all the individual reaction steps to be a peaceful sequence. To enrich the diversity and also to strengthen the practical usefulness of the methodology developed by auto‐tandem catalysis, an additive‐like component was added to induce acid‐acid‐catalyzed tandem reaction. During the reaction, the additive‐like component acted either as an activator to increase the reactivity of the starting material or a hided reagent to enable successful transformation of the intermediate. Many novel tandem reactions were established in a one‐pot manner with the aid of this strategy. Importantly, this strategy not only allows the use of simple and commercially available chemicals as substrates, but also possesses multiple merits, such as simplifying operation, lowering waste generation and enhancing synthetic efficiency and atom‐economy. A summarization of the additive‐like component‐induced auto‐tandem catalysis with an acid catalyst was given in this review, in which many acid‐acid‐catalyzed tandem reactions were discussed. The reported additive‐like components were classified as three types: oxidative type, reductive type and neutral type depending on their mechanisms in assisting the establishment of acid‐acid‐catalyzed tandem reactions. Many examples were collected and analyzed from the viewpoints of simplifying the synthesis and manifesting their superior and distinct functionalities of the additives. A perspective of this concept was also given at the end of this review.  相似文献   

2.
15‐Cyano‐12‐oxopentadecano‐15‐lactone was synthesized in 59% total yield starting from 2‐nitrocyclododecanone by Michael addition to acrylaldehyde, followed by reaction with trimethylsilylcyanide, hydrolysis, ring‐expansion, and Nef reaction. A two‐step, one‐pot synthesis of intermediate 2‐hydroxy‐4‐(1‐nitro‐2‐oxycyclododecyl)butanenitrile from 3‐(1‐nitro‐2‐oxocyclododecyl)propanal was developed and the conditions for the Nef reaction were studied. 15‐Cyano‐12‐oxopentadecano‐15‐lactam was synthesized in 40% total yield starting from 2‐nitrocyclododecanone by Michael addition to acrylaldehyde, followed by Strecker reaction, ring‐expansion, and Nef reaction. The conditions for the Strecker and Nef reactions were studied. The structures of the target compounds, intermediates, and by‐product were characterized by IR, 1H‐ and 13C‐NMR, and elemental analysis or MS.  相似文献   

3.
Fluorinated phenethyl bromides 1,2 , and 3 , prove to be totally inert under Ritter reaction conditions in the presence of either SnCl4 or AgNO3, due to the strong deactivation by the gem‐difluoro unit. Subjecting 2‐bromo‐1‐fluoro‐1‐phenylethane to SnCl4 in MeCN at elevated temperatures led to formation of 2‐methyl‐4‐phenyl‐4,5‐dihydrooxazole.  相似文献   

4.
A novel mesoporous silica‐nanotube‐supported 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilanedichloropalladium(II) complex was prepared and characterized. 3‐4,5‐Dihydroimidazol‐1‐yl‐propyltriethoxysilanedichloropalladium(II) and mesoporous silica‐supported 3‐4,5‐dihydroimidazol‐1‐yl‐propyltriethoxysilanedichloropalladium(II) were tested for catalytic activity for Heck coupling reactions between styrene and several aryl halides and Suzuki coupling reactions between phenylboronic acid and several aryl halides. Copyright © 2003 John Wiley & Sons, Ltd.  相似文献   

5.
Pummerer‐type reaction intermediate 2 of α‐(methylthio)‐N‐methoxy‐N‐methyl acetamide (1) has been found to react with 1‐alkenes to afford ene adducts 3 . N‐Methoxy‐N‐methyl‐(E,E)‐2,4‐dienamides were synthesized from the adducts 3b‐f .  相似文献   

6.
The addition of nucleophiles to C?N bonds offers a highly efficient synthetic strategy for accessing nitrogen‐containing molecules. 1 Among the well‐developed addition reactions, such as the highly efficient Mannich reaction, various C? H bond‐activated compounds including carboxylic acid derivatives, nitroalkanes, and terminal alkynes have been applied as nucleophiles to achieve different classes of amines. 2 However, employing new nucleophiles without activated C? H bonds, such as internal alkynes and allenic esters are limited when using metal catalysts. 3 Herein, we wish to report a new addition of allenic esters to C?N bonds initiated by a silver‐catalyzed 1,3‐migration of propargylic esters.  相似文献   

7.
The one‐pot four‐component reaction of benzohydrazide, acetylenedicarboxylate, aromatic aldehydes and malononitrile in ethanol with triethylamine as base catalyst afforded functionalized 1‐benzamido‐1,4‐dihydropyridines in satisfactory yields. Under similar conditions, picolinohydrazide or nicotinohydrazide can also be successfully utilized in the reactions to give corresponding functionalized 1,4‐dihydropyridines. 1H NMR data indicated that an equilibrium of cis/trans‐conformations exist in 1‐benzamido‐1,4‐dihydropyridines.  相似文献   

8.
A novel methodology is presented for the synthesis of 3‐substituted 2‐thioxo‐2,3‐dihydroquinazolin‐4(1H)‐one derivatives based on an efficient tandem multicomponent reaction using copper bromide as catalyst. This methodology is based on the multicomponent one‐pot reaction of methyl 2‐bromobenzoate, phenylisothiocyanate derivatives and sodium azide in the presence of copper bromide and l ‐proline under basic conditions. To show the generality of the method, various phenylisothiocyanates bearing electron‐donating or electron‐withdrawing functionalities were used and the desired products were obtained in high isolated yields.  相似文献   

9.
The catalytic activity of dimeric [Pd{C6H2(CH2CH2NH2)–(OMe)2,2,3}(μ‐Br)]2 and monomeric [Pd{C6H2(CH2CH2NH2)–(OMe)2,2,3}Br(PPh3)] complexes as efficient, stable and air‐ and moisture‐tolerant catalysts was investigated in the Suzuki, Stille and Hiyama cross‐coupling and homo‐coupling reactions of various aryl halides. Substituted biaryls were produced in excellent yields in short reaction times using catalytic amounts of these complexes. The monomeric complex was demonstrated to be more active than the corresponding dimeric catalyst for the cross‐coupling reaction of unreactive aryl bromides and chlorides. The combination of homogeneous metal catalysts and microwave irradiation gave higher yields of products in shorter reaction times. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

10.
An efficient synthesis of 1,2,3,4-tetrahydro-2-pyrimidinones and -thiones using ferric perchlorate as the catalyst from an aldehyde, ethyl acetoacetate, and urea or thiourea in acetonitrile was described. Compared to the classical Biginelli reaction conditions, this new method consistently has the advantage of full catalysis, good yields and short reaction time.  相似文献   

11.
Reversible‐deactivation radical polymerization (RDRP) techniques have received lots of interest for the past 20 years, not only owing to their simple, mild reaction conditions and broad applicability, but also their accessibility to produce polymeric materials with well‐defined structures. Modeling is widely applied to optimize the polymerization conditions and processes. In addition, there are numerous literatures on the kinetic and reactor models for RDRP processes, which show the accessibility on polymerization kinetics insight, process optimization, and controlling over chain microstructure with predetermined molecular weight and low dispersity, copolymer composition distribution, and sequence distribution. This review highlights the facility of the method of moments in the modeling field and presents a summary of the present state‐of‐the‐art and future perspectives focusing on the model‐based RDRP processes based on the method of moments. Summary on the current status and challenges is discussed briefly.

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12.
The data on temperature, solvent, and high hydrostatic pressure influence on the rate of the ene reactions of 4‐phenyl‐1,2,4‐triazoline‐3,5‐dione ( 1 ) with 2‐carene ( 2 ), and β‐pinene ( 4 ) have been obtained. Ene reactions 1 + 2 and 1 + 4 have high heat effects: ∆Hrn ( 1 + 2 ) −158.4, ∆Hrn( 1 + 4 ) −159.2 kJ mol−1, 25°C, 1,2‐dichloroethane. The comparison of the activation volume (∆V( 1 + 2 ) −29.9 cm3 mol−1, toluene; ∆V( 1 + 4 ) −36.0 cm3 mol−1, ethyl acetate) and reaction volume values (∆Vr‐n( 1 + 2 ) −24.0 cm3 mol−1, toluene; ∆Vr‐n( 1 + 4 ) −30.4 cm3 mol−1, ethyl acetate) reveals more compact cyclic transition states in comparison with the acyclic reaction products 3 and 5 . In the series of nine solvents, the reaction rate of 1+2 increases 260‐fold and 1+4 increases 200‐fold, respectively, but not due to the solvent polarity.  相似文献   

13.
A one‐pot method for the synthesis of 3‐amino‐7‐nitro‐1,2‐dihydroisoquinoline‐4‐carbonitriles from 2‐chloro‐5‐nitrobenzylamines and malononitrile has been developed.  相似文献   

14.
The present study a series of (E)‐5‐methoxy‐2‐styryl‐4H‐pyran‐4‐ones 6a , 6b , 6c , 6d , 6e , 6f , 6g , 6h , 6i , 6j was synthesized and evaluated for growth inhibitory inhibition against carcinoma cells. The growth inhibition study of eight carcinoma cell lines was examined and demonstrated that SKHep cells exhibit significant structure‐activity relationship in response to the tested compounds. Among them, 6f showed the most potent activity against SKHep, A549, AGS, and H460 cell lines with GI50 values of 0.17, 8.3, 3.6, 8.0 μM, respectively.  相似文献   

15.
Rhenium‐based complexes are powerful catalysts for the dehydration of various alcohols to the corresponding olefins. Here, we report on both experimental and theoretical (DFT) studies into the mechanism of the rhenium‐catalyzed dehydration of alcohols to olefins in general, and the methyltrioxorhenium‐catalyzed dehydration of 1‐phenylethanol to styrene in particular. The experimental and theoretical studies are in good agreement, both showing the involvement of several proton transfers, and of a carbenium ion intermediate in the catalytic cycle.  相似文献   

16.
Lijuan Lu  Chaoguo Yan 《中国化学》2015,33(10):1178-1188
The base mediated cycloaddition reactions of 4‐dimethylamino‐1‐phenacylpyridinium bromides with two molecular 3‐phenacylideneoxindoles in methylene dichloride afforded functionalized dispirocyclopentyl‐3,3′‐bisoxindoles in good yields and with high diastereoselectivity. The similar cycloaddition reactions of 1‐(N,N‐dialkylcarbamoylmethyl) and 1‐cyanomethyl 4‐dimethylamino‐pyridinium bromide in refluxing ethanol in the presence of triethylamine also resulted in dispirocyclopentyl‐3,3′‐bisoxindoles with high diastereoselectivity. The stereochemistry of dispirocyclopentyl‐3,3′‐bisoxindoles was elucidated on the basis of 1H NMR data and single crystal structures.  相似文献   

17.
18.
19.
A syn‐selective aza‐aldol reaction of boron aza‐enolates, generated from N‐sulfonyl‐1,2,3‐triazoles and 9‐BBN‐H, is reported. It provides a sequential one‐pot procedure for the stereoselective construction of 1,3‐amino alcohols, having contiguous stereocenters, starting from terminal alkynes.  相似文献   

20.
In this work the reactivity of 1‐metalla‐2,5‐diaza‐cyclopenta‐2,4‐dienes of group 4 metallocenes, especially of the pyridyl‐substituted examples, towards small molecules is investigated. The addition of H2, CO2, Ph?C≡N, 2‐py?C≡N, 1,3‐dicyanobenzene or 2,6‐dicyanopyridine results in exchange reactions, which are accompanied by the elimination of a nitrile. For CO2, a coordination to the five‐membered cycle occurs in case of Cp*2Zr(N=C(2‐py)?C(2‐py)=N). A 1,4‐diaza‐buta‐1,3‐diene complex is formed by H‐transfer in the conversion of the analogous titanocene compound with CH3?C≡N, PhCH2?C≡N or acetone. For CH3?C≡N a coupling product of three acetonitrile molecules is established additionally. In order to split off the metallocene from the coupled nitriles, we examined reactions with HCl, PhPCl2, PhPSCl2 and SOCl2. In the last case, the respective thiadiazole oxides and the metallocene dichlorides were obtained. A subsequent reaction produced thiadiazoles.  相似文献   

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