Jean-Noël Verpeaux

Couplage mixte entre sulfones vinyliques et réactifs de grignard en présence de sels de métal de transition: synthèse stéréosélective d'oléfines trisubstituées.

Abstract A new cross coupling reaction of vinylic sulphones with Grignard reagents catalyzed by nickel and iron complexes is described. This reaction is stereospecific: tri-substituted olefins of defined stereochemistry are obtained in good yield.

Synthèse stéréosélective des sulfones vinyliques Z et E.

Abstract The condensation of α-sulphonyl carbanions with esters or with aldehydes (followed in this case by oxidation) gives β-ketosulphones. These were reduced stereoselectively into threo β-hydroxysulphones. Basic conditions have been found where the corresponding tosylates are converted into Z vinylic sulphones whereas the erythro tosylates lead to the E isomer. The corresponding acetoxy-sulphones erythro or threo, under different alkaline conditions are converted into the same E vinylic sulphone in a “convergent” manner.

Synthèse à l'aide de sulfone. XXV: Substitution sur des sulfones: l'anion phénylsulfinate comme groupe partant dans la substitution des sulfones allyliques par des réactifs de Grignard en présence de sels de cuivre

Resume Displacement reactions of the sulphinate anion from sulfones by Grignard reagents with copper catalysis take place readily with allylic sulphones. The regio chemistry and stereochemistry of the reaction are discussed.

Organic synthesis with sulfones XXXVIII: On the mechanism of the stereospecific hydrogenolysis of vinylic sulfones by sodium dithionite

Abstract The stereospecific hydrogenolysis of vinylic sulfones by sodium dithionite in a protic medium proceeds by addition of HSO2 to give an intermediate which could be isolated after alkylation in situ to a 1,2-bissulfone. The mechanism is therefore of the β-addition-elimination type. In the case of E-2-benzenesulfonyl-2-butene and ethyl iodide a single crystalline diastereoisomer was obtained and shown to have the threo configuration by X-ray crystallography. The addition step follows the syn and the elimination step the anti stereochemistry, thus accounting for the overall retention of configuration observed.

Mechanistic investigation of the anodic oxidation of p-methoxytoluene in dry and wet acetonitrile

Abstract Alkyl aryl ethers are oxidized in acetonitrile in two very closely spaced waves. A detailed investigation has been carried out in the case of p -methoxytoluene, using both voltammetry and preparative electrolysis. The kinetics of the first anodic peak correspond to a second order rate law, both in anhydrous medium, and in the presence of water. On the preparative scale, the controlled potential electrolysis at a potential located on the first wave gives different products depending on the operating conditions. When small amounts of water were present, two new compounds were obtained as the major products: a 2,5-cyclohexadienone substituted in the 4 position by the starting compound, and the phenol resulting from an acid catalyzed rearrangement of this cyclohexadienone. A mechanism accounting for the nature of the reaction products in wet acetonitrile is proposed on the basis of the voltammetric and coulometric data as well as of the result of the electrolysis performed in the presence of 18 O labeled water.

Synthèse d'oléfines et de polyènes par doublement d'anions α-sulfonylés en présence de sels de nickel (XXII).

Abstract The lithium or magnesium derivatives of allyl, benzyl and alkyl sulphones are converted efficiently by a catalytic amount of nickel(II) acetylacetonate into symmetrical olefins in THF at 60°C. Thus, phytoene was obtained in a 74% yield from geranylgeranylsulphone.

Synthese a l'aide de sulfones—XXVI: Synthese d'alcools allyliques et de polyprenols par attach ement d'un synthon prenol en position 4 e

Resume The E-hydroxyalkylsulphone PhSO2CH2C(CH3)CHCH2OH is regioselectively and stereoselectively substituted by Grignard reagents in the presence of copper(II) acetylacetonate, giving E allylic alcohols in high yield. A recurrent synthesis of polyprenols and an efficient preparation of the African Monarch pheromone are described.

Electrosynthesis of unsymmetrical biaryls using a SRN1 type reaction

Abstract A new synthetic route to unsymmetrical biaryls is described involving an electrochemically induced chain reaction of the S RN 1 type.

Couplage des sulfones allyliques avec des reactifs de grignard en presence de cuivre synthese d'olefines

Abstract A convenient synthesis of di- and trisubstituted olefins using the coupling of Grignard reagents with allylic sulphones in the presence of copper II acetylacetonate is reported. The influence of sulphone, Grignard reagent and solvent on the regio- and stereoselectivity is discussed.

A convenient preparation of mono- or gem-di-halogenoalkenes from α-sulfonyl carbanions and halogenolithiocarbenoïds

Abstract Various α-sulfonyl carbanions have been shown to react at low temperature with di- or tri-halogenolithiocarbenoids, to give 1-mono- or 1,1-di-halogenoalkenes. Bromocarbenoids gave better results than their chloro-analogues. Reaction of di-bromolithiomethane with α-lithiated sulfones gives a high yield of vinylic bromides, the stereochemistry of which is cleanly E. Evidence is presented that the carbenoid itself is responsible for the reaction, and is not first converted into the corresponding carbene.