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Dive into the research topics where Sylvette Briand is active.

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Featured researches published by Sylvette Briand.


Tetrahedron Letters | 1988

Reduction potentials of reagents: II - a tool to anticipate yields of organometallic reactions?

Jacques-Emile Dubois; Pierre Bauer; Sylvette Briand

Abstract Reduction potentials of four cage-structure halogenated derivatives and five alicyclic and aromatic ketones have been determined by cyclic voltammetry. For the Barbier reaction these parameters are used to anticipate the behaviour of intermediates formed at the metal surface and on which the distribution product depends. Semiquantitative relationships are obtained between these potentials and yields of condensation products.


Journal of The Chemical Society-perkin Transactions 1 | 1996

Thermal fragmentation of 1-substituted spiro[adamantane-2,2′-adamantane] derivatives

John S. Lomas; Christine Cordier; Sylvette Briand

Thermolysis of 1-hydroxy- or 1-acetoxy[1]diadamantane gives mixtures of 3-(adamantylidene)-bicyclo[3.3.1]non-6-ene,3, 3-(2-adamantyl)bicyclo[3.3.1]nova-2,6- and -2,7-dienes, 4, and 2-(3-noradamantyl)-2,4-dehydroadamantane, 7. At low conversion 3 and 7 are the major products, while one isomer of 4, the 2,6-diene, predominates in the equilibrium mixture. Pd/C-catalysed hydrogenation of the dienes in ethanol gives first 3-(2-adamantyl)bicyclo[3.3.1]non-2-ene, 5, and then endo-3-(2-adamantyl)bicyclo[3.3.1]nonane, 6. Hydrocarbon 7 is not hydrogenated under these conditions; it is converted into a mixture of 3 and 4(2,6) upon heating. Mechanisms for the fragmentation of the 1-[1]diadamantyl carbocation are discussed. While a 1,4-hydride shift may contribute to the reactions of the [1]diadamantane system, molecular mechanics calculations suggest that the ready formation of an olefin from 1-hydroxyspiro [adamantane-2,9′-bicyclo[3.3.1]nonane] is best interpreted in terms of a 1,5-hydride shift involving the chair-boat conformation of the bicyclononane system.


Phosphorus Sulfur and Silicon and The Related Elements | 1996

NOUVEAUX DECONTAMINANTS. DESTRUCTION DE TOXIQUES ORGANOPHOSPHORES ET SOUFRES PAR L'ACIDE MONOPEROXYPHOSPHORIQUE

Claude Lion; Mir Hedayatullah; Fabrice Pirès; Claude Charvy; Sylvette Briand; Gilbert Magnaud; Gerard Delmas; Et Henri Sentenac-roumanou

Abstract H3PO5, monoperoxyphosphoric acid easily prepared by the reaction of H2O2 with P2O5 in acetonitrile, is a very good decontamination agent. The destruction of toxic sulfur and phosphorus agents is completly achieved in very short time.


Journal of The Chemical Society-perkin Transactions 1 | 1996

Thermal rearrangement of 1-substituted spiro[adamantane-2,2′-adamantane] derivatives

John S. Lomas; Christine Cordier; Sylvette Briand; Jacqueline Vaissermann

Tertiary 1-halospiro[adamantane-2,2′-adamantane] derivatives (1-halo[1]diadamantanes) have been synthesised by reaction of the 1-[1] diadamantyl cation with appropriate nucleophiles. Thermolysis of 1-chloro- or 1-bromo-[1]diadamantane, but not the 1-fluoro derivative, gives the corresponding secondary 4-halo derivative in good yield. By 1H and 13C NMR spectroscopy and by X-ray crystallography it has been established that the 4-bromo [1]diadamantane isolated is the anti isomer, with the Br–C–C–Cspiro torsion angle close to 170°, this being the less strained of the two possible 4-substituted isomers, according to molecular mechanics calculations. Possible mechanisms for the rearrangement are discussed.


Journal of The Chemical Society-perkin Transactions 1 | 1992

Ring opening of a formal cyclopentylmethyl radical in the thermolysis of di(tert-alkyl)(1-norbornyl)methanols

John S. Lomas; Sylvette Briand

In the thermolysis of di(1-adamantyl)(1-norbonyl)methanol, Ad2NorCOH, 1a, in toluene at 220–265 °C, C–C bond cleavage within the norbornyl group of the first-formed (1-adamantyl)(1-norbornyl)ketyl radical (by loss of Ad˙) leads to ring-opened ketones and several ketonic cross-products. These are isomeric with the secondary alcohol, AdNorCHOH, and with the regular cross-product, AdNorSCOH (S = benzyl), respectively, also present in the product mixture. Formation of the ring-opened thermolysis products is particularly favoured by high temperature and the use of deuteriated solvent, which slows hydrogen transfer from the solvent to the intermediate ketyl radical. The new products are cyclopentane derivatives, formed by cleavage of the norbornyl C(1)–C(2) bond, in agreement with MM2 calculations on the transition states. Self-consistent values for the cage effect have been determined by measuring the extent of 1-[2H] labelling of the adamantane formed in [2H8] toluene and by scavenging the ketyl radical with benzenethiol in [1H8] toluene. The product composition of the scavenger-free reaction in [1H8] or [2H8] toluene has been interpreted by kinetic simulation based on the steady state approximation, a Simplex procedure being used to optimise several rate constants, in particular those for hydrogen transfer from toluene to the ketyl radical and ring opening of the latter. The Arrhenius pre-exponential factor and activation energy are both much greater for ring opening than for hydrogen transfer.


Tetrahedron Letters | 1989

Hydrogen atom transfer in the reactions of thermally-generated di-t-alkylketyl and 1-adamantyl radicals

John S. Lomas; Sylvette Briand

Abstract In the thermolysis of tri-(1-adamantyl)methanol about 55% of the di-(1-adamantyl)-ketyl and 1-adamantyl radicals escape from the solvent cage, the former transferring hydrogen to benzophenone and the second abstracting hydrogen from the solvent, toluene, with isotope effects on the latter reaction consistent with tunnelling.


Tetrahedron | 1984

Synthese de molecules encombrees: Recherche des conditions optimales de condensation dbs composes organolithiens cage sur differents substrats organiques

Gérard Molle; Sylvette Briand; Pierre Bauer; Jacques-Emile Dubois


Journal of Organic Chemistry | 1991

Reactions of thermally generated tert-butyl and di(tert-alkyl) ketyl radicals in toluene: cage effects and hydrogen transfer

John S. Lomas; Sylvette Briand; Dominique Fain


Journal of Organic Chemistry | 1990

Reactions of thermally generated 1-adamantyl and Di(1-adamantyl)ketyl radicals in toluene

John S. Lomas; Dominique Fain; Sylvette Briand


Bulletin des Sociétés Chimiques Belges | 2010

Nouveaux decontaminants generation “in situ” d'un peracide par action d'un persel sur un initiateur, reactivite de ce peracide vis-a-vis du paraoxon

Claude Lion; Mir Hedayatullah; Claude Charvy; Sylvette Briand; Stephane Vincent; Laurent Fosset; Gerard Delmas; Gilbert Magnaud; Michel Desgranges; Henri Sentenac-Roumanou

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John S. Lomas

Spanish National Research Council

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Gerard Delmas

Ministère de la Défense

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Gilbert Magnaud

Ministère de la Défense

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