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Dive into the research topics where Jean-Claude Négrel is active.

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Featured researches published by Jean-Claude Négrel.


Tetrahedron Letters | 1994

New perspectives in the formation of the Grignard reagent

Eric Péralez; Jean-Claude Négrel; Michel Chanon

Abstract Inhibitors, in very low concentration, inhibit the reaction between 1-bromo-3-methylbutane and magnesium obtained by vaporization of metal. For such a magnesium derivative, the inhibitors cannot play the role of “killers” for active sites. A chain reaction for the formation of the Grignard reagent is proposed.


Tetrahedron | 1995

Further Evidence for the Radical Chain Character of Grignard's Reagent Formation. Use of Free Radical Clock in Conjunction with Changes in Concentration of Active Mg.

Eric Péralez; Jean-Claude Négrel; Michel Chanon

Abstract The reaction of endo-5-(2′-haloethyl)-2-norbortiene (X=I, Br, Cl) with active Mg obtained by metal vaporization yields both cyclized and uncyclized organomagnesium compounds. The ratio cyclized / uncyclized increases in the order Cl


Tetrahedron Letters | 1995

Drastic effects of dioxygen on the selectivity of reduction by LiAlH4. Milder conditions made possible by strictly anaerobic conditions

Eric Péralez; Jean-Claude Négrel; Michel Chanon

Abstract Reduction of the gem-disubstituted cyclopropane 1 with LiAlH 4 yields different results under strictly anaerobic conditions and loosely anaerobic ones. Under strictly anaerobic conditions, (+)-1-bromo-2,2-diphenylcyclopropanecarbinol 2 is quantitatively reduced to 3 with complete racemization. These observations are explained by a radical chain mechanism. They open the way to reductions by LiAlH 4 under mild conditions.


Tetrahedron Letters | 1996

Occurence of a radical intermediate during the reductive decyanation of an α-sulfonitrile with LiAlH4

J.-M. Mattalia; Y. Berchadsky; Eric Péralez; Jean-Claude Négrel; P. Tordo; Michel Chanon

Abstract LiAlH 4 reduction of 2-(isopropylsulfonyl)-bicyclo[2.2.1]hept-5-ene-2-carbonitrile 1 gave the reduced product 2 resulting from the first reported LiAlH 4 induced α-sulfonitrile decyanation. Experiments using LiAlD 4 suggest the involvement of a radical intermediate. Using a radical-probe, the spiranic compound 6 characteristic of a radical intermediate has been detected. Electrochemical measurements do fit with a SET from LiAlH 4 to the nitrile.


Comptes Rendus De L Academie Des Sciences Serie Ii Fascicule C-chimie | 2001

Extension of the e.t. mechanism of aromatic nitration to the formation of Grignard reagents of RX (R = alkyl, aryl, cyclopropyl, vinyl). The ion pair collapse versus radical pair collapse hypothesis

Ulf Berg; Nicolas Bodineau; Jean-Claude Négrel; Jean-Marc Mattalia; Vitaliy Timokhin; Kishan Handoo; Caroline Marchi; Michel Chanon

Abstract The ion pair collapse versus radical pair collapse hypothesis is proposed for the Grignard reagent formation as an extension of the e.t. mechanism of aromatic nitration. Such a scheme, never examined before for the Grignard reaction, could explain the evolution of the ‘free radical character’ depending on experimental conditions and the nature of the substrate.


Archive | 1989

Metal Vapor Reactivity of Copper Toward Substituted Bromobenzenes. Comparison with the Classical Ullmann Coupling Reaction

Jean-Claude Négrel; R. W. Zoellner; Michel Chanon; Françoise Chanon

The reaction of Copper vapors with a film of bromobenzenes in a solution of methylcyclohexane - tetrahydrofuran maintained at - 120°C mainly yields reduction and coupling products. The low temperature contrasts with the severe reaction conditions used when metallic copper is used as a promoter. In terms of overall conversion (percent of copper effectively used to induce chemical transformation) o-chloro; o-amino and p-RO substituents play a beneficial role. In terms of coupling /reduction ratio, unsubstituted bromobenzene yields the best results. As in the classical Ullmann reaction nitro group induces far more coupling when it is situated in ortho of bromine than when it occupies the meta or (even worse) para position. For some substrates, THF used as cosolvent reacts with the intermediates organometallic to yield the condensation of benzene with an open form of THF. Ortho substituents of apropriate structure seem able to stabilize metallic atoms of Cu.


Main Group Metal Chemistry | 1998

DETERMINATION OF THE SIZE OF MAGNESIUM AGGREGATES OBTAINED BY VAPORIZATION. QUANTUM EFFECT AND NATURE OF THE ACTIVE SITES IN THE MAGNESIUM SAMPLES USED FOR THE PREPARATION OF GRIGNARD REAGENTS

Eric Péralez; Jean-Claude Négrel; Annick Goursot; Michel Chanon


Main Group Metal Chemistry | 1999

MECHANISM OF THE GRIGNARD REAGENT FORMATION - PART 1 - THEORETICAL INVESTIGATIONS OF THE MGN AND RMGN PARTICIPATION IN THE MECHANISM

Eric Péralez; Jean-Claude Négrel; Annick Goursot; Michel Chanon


Main Group Metal Chemistry | 1999

MECHANISM OF THE GRIGNARD REAGENT FORMATION - PART 2 - AN AB INITIO STUDY OF THE RMgX FORMATION FROM THE RMgn(I) CLUSTERS

Eric Péralez; Jean-Claude Négrel; Annick Goursot; Michel Chanon


European Journal of Organic Chemistry | 2010

About the Inhibition of Grignard Reagent Formation by p-Dinitrobenzene: Comparing the Mechanism of Grignard Reagent Formation and the SRN1 Mechanism

Nicolas Bodineau; Jean-Marc Mattalia; Hassan Hazimeh; Kishan Handoo; Vitaliy Timokhin; Jean-Claude Négrel; Michel Chanon

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Michel Chanon

Centre national de la recherche scientifique

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Eric Péralez

Centre national de la recherche scientifique

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Annick Goursot

École Normale Supérieure

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Jean-Marc Mattalia

Centre national de la recherche scientifique

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Kishan Handoo

Centre national de la recherche scientifique

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Nicolas Bodineau

Centre national de la recherche scientifique

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Vitaliy Timokhin

Centre national de la recherche scientifique

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Hassan Hazimeh

Centre national de la recherche scientifique

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