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Nitrogen Nucleophiles (nitrogen + nucleophile)

Distribution by Scientific Domains
Chemistry100%

Selected Abstracts

Thermodynamic Study of ,H Complexes in Nucleophilic Aromatic Substitution Reactions: Relative Stabilities of Electrochemically Generated Radicals

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 14 2008
Iluminada Gallardo
Abstract The mechanism for the electrochemical oxidation of ,H complexes, such as 1-hydro-1-alkoxy/sulfoxy or -fluoro-2,4-dinitro/2,4,6-trinitrocyclohexadienyl anions, has been widely studied by means of cyclic voltammetry and controlled-potential electrolysis. Previous studies have shown that the electrochemical oxidation of ,H complexes, formed by the addition of carbon or nitrogen nucleophiles followed by a two electron mechanism, corresponding to the formal elimination of the hydride anion (nucleophilic aromatic substitution of hydrogen mechanism, the NASH mechanism). For these ,H complexes (Nu, = OH,, ,OR, ,SR, ,F), the electrochemical reaction takes place by a one-electron mechanism and is followed by the radical elimination of the leaving group with the consequent recovery of the starting material. This mechanism is similar to that proposed for the electrochemical oxidation of ,X complexes (nucleophilic aromatic substitution of a heteroatom, the NASX mechanism). The operating mechanism in each case, the NASH or NASX, can be rationalized in terms of thermodynamics. The standard potentials of the , complex and/or the leaving group as well as the bond dissociation energies (BDEs) are determinant factors. This study has not led to a significant improvement in the electrochemical preparation of aromatic-substituted compounds, but does help to understand and predict the usefulness or uselessness of using the nucleophilic aromatic substitution route to obtain a desired product. Finally, the current approach extends the electrochemical methodology to different chemical fields, for example, to general nondestructive methods for the detection, identification, and quantification of either organic pollutants or explosives in different solvents. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source]

Thiophenylhydrazonoacetates in heterocyclic synthesis

HETEROATOM CHEMISTRY, Issue 1 2004
Rafat M. Mohareb
Benzo[b]thiophen-2-yl-hydrazonoesters 4 were synthesized by coupling of 2-diazo-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxamide (1) with either ethyl cyanoacetate or ethyl acetoacetate. The reactivity of 4 toward a variety of nitrogen nucleophiles was investigated to yield pyrazole, isoxazole, pyrimidine, triazine, pyrazolopyridine, and pyrazolopyrimidine derivatives. © 2003 Wiley Periodicals, Inc. 15:15,20, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/.hc10205 [source]

Efficient Cross-Coupling Reactions of Nitrogen Nucleophiles with Aryl Halides in Water

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 5 2009
Yong-Chua TeoArticle first published online: 17 MAR 200
Abstract A facile and practical strategy has been developed for the N -arylation of nitrogen nucleophiles with aryl halides catalyzed by a combination of iron(III) chloride [FeCl3] and dimethylethylenediamine (dmeda) in water. A variety of nitrogen nucleophiles including pyrazole, indole, 7-azaindole and benzamide afforded the N -arylated products in the presence of the catalytic system (in up to 88% yield). [source]

One-Pot Synthesis of Highly Substituted Allenylidene Derivatives via Palladium- or Nickel-Catalyzed Tandem Michael Addition,Cyclization Reaction

ADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 1-2 2009
Yun Shi
Abstract A simple and tandem synthetic approach, which offers an efficient, direct route to highly substituted indenes, has been developed by palladium- or nickel-catalyzed cyclization of propargylic compounds and nitrogen nucleophiles. The reaction takes place under mild conditions, and a possible mechansim is proposed. [source]

Ethyl {4-[2-(saccharin-2-yl)acetylsulfamoyl]phenylazo}cyanoacetate in the synthesis of polyfunctionally heteroaromatic derivatives

JOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2009
A. A. Aly
An efficient and direct one-pot reaction of ethyl saccharinylcyanoacetate derivative 3 with a variety of active methylene reagents and nitrogen nucleophiles afforded novel series of polyfunctionally substituted heteroaromatic derivatives 5,13, respectively. The pyrazole derivative 13 was seemed to be the excellent precursors for the synthesis of pyrazolo[1,5-a]pyrimidine derivatives 14,24. The antimicrobial screening of some synthesized products was evaluated against some selected bacteria and fungi. The structures of the synthesized derivatives were established by elemental and spectral data. J. Heterocyclic Chem., (2009). [source]

Reactivity of Intein Thioesters: Appending a Functional Group to a Protein

CHEMBIOCHEM, Issue 9 2006
Jeet Kalia
Abstract The success of genome sequencing has heightened the demand for new means to manipulate proteins. An especially desirable goal is the ability to modify a target protein at a specific site with a functional group of orthogonal reactivity. Here, we achieve that goal by exploiting the intrinsic electrophilicity of the thioester intermediate formed during intein-mediated protein splicing. Detailed kinetic analyses of the reaction of nitrogen nucleophiles with a chromogenic small-molecule thioester revealed that the ,-hydrazino acetyl group was the optimal nucleophile for attacking a thioester at neutral pH to form a stable linkage. A bifunctional reagent bearing an ,-hydrazino acetamido and azido group was synthesized in high overall yield. This reagent was used to attack the thioester linkage between a target protein and intein, and thereby append an azido group to the target protein in a single step. The azido protein retained full biological activity. Furthermore, its azido group was available for chemical modification by Huisgen 1,3-dipolar azide,alkyne cycloaddition. Thus, the mechanism of intein-mediated protein splicing provides the means to install a useful functional group at a specific site,the C terminus,of virtually any protein. [source]