Jacques Gore

Synthèse de diènes-1,3 et de styrènes fonctionnalisés par carbopalladation catalytique d'allènes

Abstract The palladium (O) catalyzed reaction of aryl and vinyl halides with allenes in the presence of sodium ethyl malonate leads with good yields and in certain cases with high stereoselectivity to styrenes and 1,3-butadienes derivatives.

Carbopalladation of allenic hydrocarbons. : A new way to functionalized styrenes and 1,3-butadienes.

Abstract The palladium-catalyzed coupling reaction of allenes, vinyl or aryl halides and stabilized carbanions is described : π-allyl palladium complexes are formed by addition of a vinyl or an aryl-palladium complex to an allenic hydrocarbon and trapped by the sodium enolate of diethyl malonate giving rise with good yields to β-butadienyl or β-styryl malonates. With monoalkyi allenes, the reaction is regiospecific with attack of the nucleophile on the unsubstituted carbon of the Intermediate π-allyl complex and in many cases highly stereoselective with the predominant formation of the E configuration for the trisubstituted double bond of the diene. This configuration was demonstrated by 1 H NMR using NOE difference spectroscopy.

Reactive D'esters α-Alleniques. Synthese regiospecifique de diesters γ-alleniques et de dienes−1,3.

Abstract The palladium (o) catalyzed reaction of sodium ethylmalonate with α-allenic acetates and α-allenic phosphates leads exclusively to β-allenic malonates. The uncatalyzed reaction of Grignard reagents with the same phosphates gives 1,3-dienes regiospecifically and with high stereoselectivity.

Synthese de Δ-2 butenolides a partir du furfural.

Resume The reaction of two molecular equivalents of organolithium derivatives with 4-hydroxy-2-butenolide (easily prepared from furfural) leads to 4-substituted butenolides with excellent yields.

Synthése d'alcools α-alléniques par réaction d'organochromiques propargyliques sur les aldéhydes et les cétones

Resume Les bromures propargyliques peuvent etre condenses avec les aldehydes et les cetones en presence du reactif de Hiyama (2 CrCl3+LiAlH4 dans le THF) pour conduire a des alcools α-alleniques, a des alcools homopropargyliques ou au melange des deux. La selectivite (ou specificite) de cette reaction est influencee par la substitution du bromure propargylique, par la structure de la cetone et par la presence de HMPT dans le milieu reactionnel. Dans de nombreux cas, lalcool α-allenique a ete specifiquement ou tres selectivement obtenu. Le mecanisme de la reaction ainsi que linfluence des divers parametres sont discutes.

New Preparation of Bromoallenes

Abstract Bromoallenes are useful intermediates in organic synthesis (1) and also occur in a few natural products (2). They usually are prepared from propargylic alcohols by reaction with hydrobromic acid in the presence of cuprous bromide (2) but these conditions are usually drastic. A milder method has been reported but its scope is more limited (4).

Carbopalladation des alkylidenecyclopropanes-II capture intramoleculaire de l'organopalladique intermediaire

Resume The reaction of an alkylidenecyclopropane of type 1, bearing an Internal nucleophile(β-diester , β-keto-ester, β-sulfonyl-ester , amine) with lodobenzene in the presence of catalytic amounts of a palladium (o) complex leads to cyclic compounds 3 and (or) 4 depending on the number of carbon atoms between the nucleophilic moeity and the double bond. These compounds result from the intramolecular attack of a II-allyl-palladium formed by isomerisation of the initial α-cyclopropanic σ-palladic species. This isomerisation does not occur when n = 4 and the product then results from the direct attack of the carbon nucleophile on the Csp3-palladium bond of the cyclopropanic σ-complex.

Transposition d'oxy-cope a temperature ambiante catalysee par le dichlorure de palladium-bisbenzonitrile.

Resume Tertiary hexa-1, 5-diene-3-ols substituted on the carbon 5 ( 1 ; R 1 , R 3 ≠ H) are isomerized at room temperature into δ-ethylenic ketones 2 by using 0,1 molar equivalent of the entitled palladium (II) complex. The yield of the transformation is good and the stereo-selectivity is higher than 90 %.

Formation de derives cyclopenteniques et vinylcyclopropaniques lors de la carbopalladation de diesters et d' α-sulfonylesters alleniques

Resume La carbopalladation des enolates des composes allenlques fonctlonnels 3 par un organopalladique vinylique ou arylique conduit avec de bons rendements aux composes cycliques 5 et (ou), 6 resultant de lattaque de lanion sur lun ou lautre des carbones terminaux du complexe π-allylique intermediaire 4 . La regioselectivite depend principalement de la nature du groupe vinylique entrant, la formation du cyclopropane netant observee que dans les reactions mettant en jeu le bromure de vinyle. Elle parait etre le reflet dun equilibre entre les structures syn et anti du π-allyl palladium 4 issu de la carbopalladation.

Organopalladiques issus des esters d'alcools α-alleniques : reactions avec les anions delocalises

Resume Les esters dalcools α-alleniques, et en particulier les phosphates, reagissent sur les anions de s-diesters, s-cetoesters et α-phenylsulfonylesters, en presence de quantites catalytiques dun complexe de palladium(O) pour conduire par substitution directe a des allenes s-difonctionnels. Cette reaction permet dobtenir rapidement in intermediaire de la synthese de la pheromone de la bruche du haricot sec.