Jean-Claude Négrel
Centre national de la recherche scientifique
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Featured researches published by Jean-Claude Négrel.
Tetrahedron Letters | 1994
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
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
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
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
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
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
Eric Péralez; Jean-Claude Négrel; Annick Goursot; Michel Chanon
Main Group Metal Chemistry | 1999
Eric Péralez; Jean-Claude Négrel; Annick Goursot; Michel Chanon
Main Group Metal Chemistry | 1999
Eric Péralez; Jean-Claude Négrel; Annick Goursot; Michel Chanon
European Journal of Organic Chemistry | 2010
Nicolas Bodineau; Jean-Marc Mattalia; Hassan Hazimeh; Kishan Handoo; Vitaliy Timokhin; Jean-Claude Négrel; Michel Chanon