共查询到20条相似文献,搜索用时 14 毫秒
1.
Dmitriy A. Sibgatulin 《Tetrahedron letters》2007,48(15):2775-2779
The reaction of ‘push-pull’ enamines with trifluoromethyl-containing 1,3-dicarbonyl compounds was investigated. It was found that the reaction is sensitive both to the structure of the enamines and to reaction conditions. As a result, a set of various trifluoromethyldialkylanilines was obtained. 相似文献
2.
The introduction of a 1,3-diacetylpyridine moiety, as an additional binding niche in a macrocyclic receptor ligand containing a conjugated, push-pull malonate functionality, leads to, in addition to the 1:1 binding stoichiometry, the equilibrium formation of multiple complexes, specifically 1:2, 2:1, and 3:1 ligand:metal complexes with lanthanide trications. Various binding modes elicit distinctive responses in the visible region, which enhance the potential recognition of lanthanide ions. This paper also highlights the usefulness of a full factor analysis in the elucidation of complex binding phenomena. 相似文献
3.
Jeroni Morey Maria Orell Miquel Àngel Barceló Pere M. Deyà Antoni Costa Pablo Ballester 《Tetrahedron letters》2004,45(6):1261-1265
We report the synthesis of two new anion receptors of a covalently linked 1,3,5-triarylbenzoamido-crown ether. Our results show that combined with a picrate salt they act by means of an intermolecular charge transfer process (EDA complex), as naked-eye sensors for basic anions, especially for sodium phytate in DMSO/H2O (1:1). 相似文献
4.
The reaction of 2-chloro-3-oxo-3,4-dihydro-2H-1,4-benzothiazines with ‘push-pull’ enamines was investigated. The reaction with the enamines occurs at the β-carbon atom in the presence of a small excess of triethylamine. As a result, a set of 3-oxo-3,4-dihydro-2H-1,4-benzothiazin-2-yl derivatives of 1,3-dicarbonyl compounds and benzothiazinone spiro derivatives was prepared. On acidic hydrolysis of ethyl 2-ethyl-3-(methylimino)-2-(3-oxo-3,4-dihydro-2H-1,4-benzothiazin-2-yl)butanoate, a new rearrangement affording ethyl 11-ethyl-2,3-dimethyl-4-oxo-2,3,4,5-tetrahydro-1H-2,5-methano-6,1,3-benzothiadiazocine-11-carboxylate was discovered. A plausible mechanism and factors influencing the course of the reaction are discussed. 相似文献
5.
Fang Xie 《Tetrahedron》2008,64(13):2906-2914
Fluorogenic reactions have broad applications in biolabeling, combinatorial synthesis of fluorescent dyes, and materials development. It was recently reported that the highly selective and efficient Cu(I)-catalyzed azide-alkyne cycloaddition (CuAAC) reaction can be employed in designing new types of fluorogenic reactions. In this study, we report a fluorogenic reaction using anthracene azides as starting materials. The fluorescence of the anthryl core can be greatly inhibited upon introducing electron-donating azido groups in the proximity. Such weakly fluorescent anthracene azides demonstrate high reactivity with a variety of alkynes under the CuAAC conditions producing a strongly fluorescent triazole product with high quantum yields. This reaction can be used in the synthesis and screening of fluorescent dyes combinatorially. Compared with most existing methods, the fluorogenic CuAAC reaction is a much milder and simpler technique to prepare large libraries of fluorescent dyes without further purification. In order to demonstrate the efficiency of using anthracene azides for biolabeling applications, both small molecules and biomolecules including the multialkyne-derivatized cowpea mosaic virus and tobacco mosaic virus had been studied. 相似文献
6.
Alexey V. Ustinov 《Tetrahedron》2008,64(7):1467-1473
Terminal alkyne-containing phosphoramidite and solid support were prepared and used for the synthesis of 5′- and 3′-alkyne-modified oligonucleotides. The copper-catalyzed Huisgen [3+2] cycloaddition reaction in water-DMSO was used for the efficient preparation of perylene diimide-oligonucleotide conjugates suitable for constructing various types of PDI-modified DNA duplexes. 相似文献
7.
Vimal K. Bhardwaj 《Tetrahedron》2008,64(22):5384-5391
A new set of tripodal receptors based upon an aromatic platform have been synthesized in high yields. The compounds have been characterized by spectroscopic techniques and by single crystal X-ray crystallography. These receptors are found to have good extraction ability and high transport rate for Ag(I). The receptor with imine linkages exhibits weak fluorescence emission bands at λmax=413 and 540 nm, upon excitation at λmax=365 nm. The fluorescence spectrum of the receptor shows enhancement in the intensity of the signal at 413 nm on binding with the Ag+ cation. No such significant changes are observed with other metal ions. An absorption at ∼365 nm is typical of an intraligand (π-π∗) transition involving the imine chromophore, which produces a weak emission band at 413 nm due to quenching caused by PET from a neighboring -OH group. Participation of OH group in coordination to the metal ion reduces PET and an enhancement of fluorescence intensity is observed, signaling recognition of the metal ion. 相似文献
8.
A new, high-yielding methodology for reducing hydrazones to hydrazines is described, which allows the synthesis of different mono-, di- and trisubstituted hydrazines. Moreover, the reduction step can be followed by an in situ reaction with a carboxylic acid making possible a ‘one-pot’ synthesis of trisubstituted hydrazides. The method is relatively general and, in principle, suitable for industrial applications. 相似文献
9.
Eufrânio N. da Silva Júnior Kelly C.G. de Moura Claudia J. Nascimento Antônio V. Pinto 《Tetrahedron letters》2009,50(14):1575-2418
The structure of ‘lapachol peroxide’ was published by Hooker in 1936; however, we recently discovered a mistake in the originally proposed structure; the correct structure, according to X-ray spectroscopy, is given here. 相似文献
10.
Mike M.K BoysenThisbe K Lindhorst 《Tetrahedron》2003,59(22):3895-3898
Two new pathways to introduce carbohydrate derivatives into dendritic carbosilane structures were explored. Pathway one utilised alcoholysis of a chlorosilane with a protected hydroxyethyl glycoside resulting in Si-O linkages. Pathway two proceeds via a hydrosilylation reaction of a protected allyl glycoside with a carbosilane containing Si-H end groups in the presence of a platinum catalyst, thus leading to Si-C linked structures. 相似文献
11.
Delphine Didier 《Tetrahedron》2007,63(4):941-946
The syntheses of oligothiophenes 1 and 2 comprising two different types of peripheral substituents, namely alkyl and perfluoroalkyl, is reported. The key synthetic step is the Pd-catalyzed cross-coupling of perfluoroalkylated bromide 3 with an appropriate boronate. This molecular design is expected to promote unusual two-layer packing, which is of interest for application in electronic devices. Quaterthiophene 1 forms smectic mesophase, though in the narrow temperature range, and is suitable for the fabrication of thin films by solution processing methods. 相似文献
12.
Jalal Lazaar 《Tetrahedron letters》2005,46(22):3811-3813
Cerpegin (1) was synthesized through a ‘one-pot’ reaction in 71% overall yield. Lithiation of commercially available 2-methoxynicotinic acid (2) as its lithium salt using LTMP, followed by addition of acetone at low temperature and a specific acidic treatment of the intermediate 3 thus obtained, gave the 1,1-dimethyl-3,4-dioxo-1,3,4,5-tetrahydrofuro[3,4-c]pyridine (4). The latter was finally selectively alkylated using methyl iodide and caesium carbonate to afford cerpegin (1). 相似文献
13.
Rose Haddoub 《Tetrahedron letters》2009,50(7):741-5582
An efficient approach for the immobilization of a series of analogs of aloisine A, an in vitro inhibitor of protein kinases, to polymeric supports via a [3+2] cycloaddition reaction is reported. 相似文献
14.
Yong-Suk Cho 《Tetrahedron letters》2010,51(29):3852-3854
A fluorescent probe selectively senses inorganic mercury in the turn-on mode through a mercury ion-promoted hydrolysis reaction that leads to a coumarin, among various other metal species except Au(III). 相似文献
15.
A versatile method for the synthesis of carbamates from an ‘in-situ’ generated polymer-supported chloroformate resin is presented. BTC (bis-trichloromethyl carbonate) is used as phosgene equivalent to afford a supported chloroformate, which, by sequential ‘one-pot’ reaction with a variety of alcohols and amines, furnishes the corresponding carbamates in high yields and purities. 相似文献
16.
N-tert-Butylamides are readily converted into the corresponding carboxylic acids by simple nitrosation. The process, which occurs under mild nonaqueous conditions, leaves carboxylic esters untouched and transforms multicomponent reaction products into useful building blocks for further synthetic elaboration. 相似文献
17.
Moloy Sarkar 《Tetrahedron letters》2006,47(43):7575-7578
An ‘off-on’ fluorescence chemosensor for the selective signalling of Cr(III) has been designed exploiting the guest-induced inhibition of the photoinduced electron transfer signalling mechanism. The system shows an approximately 17-fold Cr(III)-selective chelation-enhanced fluorescence response in tetrahydrofuran and the system is highly selective against the background of environmentally and biologically relevant metal ions. 相似文献
18.
Rafik Karaman 《Tetrahedron letters》2008,49(41):5998-6002
Ab initio at HF/6-31G and HF/6-31G(d,p) levels, AM1 and molecular mechanics calculations of thermodynamic and kinetic parameters for Menger’s system 1-3 (an important enzyme model) indicate that the remarkable enhancement in the proton transfer process is largely the result of a strain effect, and this strain is a function of the bond distance between the two reacting centers and the value of the angle of attack. 相似文献
19.
M. Dolores Otero 《Tetrahedron letters》2005,46(50):8681-8683
2,4,6-Trimethylpyridine-3,5-dicarbonitrile has been obtained as the main product after the electrolysis of acetonitrile in the presence of tetrabutylammonium bisulfate as supporting electrolyte using a divided cell with a medium porosity diaphragm. 2,6-Dimethylpyridine-3,5-dicarbonitrile and 2,6-dimethylpyridine-3,4,5-tricarbonitrile have also been obtained in minor quantity. This process, which takes place with participation of both electrodes, is an example of a paired electrosynthesis. 相似文献
20.
Tomáš Tobrman 《Tetrahedron letters》2004,45(2):273-276
Alkenylation of 9-benzyl-6-halopurines with alkenes does not proceed under conventional Heck conditions. However, in the presence of triethylammonium formate a mixture of the corresponding saturated products was obtained. In contrast to the classical Heck reaction, the regioselectivity of this process is low giving a mixture of both α- and β-products regardless of the electronic nature of the substituent on the double bond of the alkene. 相似文献