M. Lequan

Réaction de condensation des dérivés propargyliques et alléniques de l'étain sur le chloralétude cinétique

Abstract The reaction of tin propargylic and allenic compounds with chloral can be carried out in equilibrium or non-equilibrium conditions for the organometallic derivatives. Quantitative investigation has been made and the reaction mechanism discussed according to the kinetic data.

Les organostanniques chiraux. synthese et dedoublement organostanniques

Abstract p -(Triorganostannyl) benzoic acids have been prepared and separated into their diastereomeric salts by fractional crystallization.

Composés propargyliques et alléniques du Si, Ge, Sn chiraux possédant en α un carbone asymétrique mise en évidence des diastéréoisomères

Abstract The propargylic R 1 R 2 R 3 MCH(CH 3 )CCH and allenic R 1 R 2 R 3 MCHCCHCH 3 compounds (M = Si, Ge, Sn) with two neighbouring asymmetric centres exist in two diastereotopic erythro and threo forms observable in NMR.

Equilibre cinetique et isomerisation propargyl-allenylique des derives stanniques β-insatures

Abstract It is shown that propargylic tin compounds can exist in equilibrium with their allenic isomers. This tautomeric equilibrium is not spontaneous but must be catalysed by electron-donor solvents or by Lewis acids. An ion pair mechanism is proposed according to entropy and activation volume.

Synthese et dedoublement d'un compose stannique chiral

Resume p -(Phenylmethylisopropylstannyl)benzoic acid was prepared and resolved by fractional crystallisation of its (−)-brucine salt from methanol. The least soluble diastereoisomer yields the (−)-acid [α] 22 D = −0.50° in CHCl 3 and from the mother liquor repeated fractionations gave the other impure diastereoisomer leading to the (+)-acid [α] 22 D = +0.34° in CHCl 3 . Diazomethane in ethereal solution reacted with both acids to give the corresponding methyl esters.

Comportement de LiAlH4 en fonction de la dilution dans la racemisation d'un silane optiquement actif en milieu thf

Abstract The optically active methylphenyl-α-naphthylsilane racemises quickly in tetrahydrofuran in the presence of LiAlH4. Kinetic results show a different behaviour of the hydride depending on its concentration. Activation parameters have been obtained and mechanisms proposed.

Synthese d'un triorganostannyl benzaldehyde chiral

Resume p -(Methylphenylisopropylstannyl)benzaldehyde has been prepared and resolved by menthyl carbazate in ethanol ([α] 20 D –34.6°). Functional exchange with acetone of the less soluble diastereomer catalysed by traces of p -toluenesulfonic acid yields the optically active aldehyde with [α] 20 436 +0.35°.

Les tetraorganoetains optiquement actifs. Synthese et stereochimie dynamique sur l'atome de metal

Abstract A general method of preparation of optically active organotin compounds by direct synthesis from R 1 R 2 R 3 SnX has been proposed. This method is based on attack of organometallic reagents on the tin atom attached to a chiral leaving group. Cinchonine and cinchonidine are the best inductors found.

Synthese et proprietes de quelques amines stanniques chirales; essais de dedoublement

Abstract Synthesis and properties of chiral stannic amines are investigated. Tentative resolution has been carried out with tartaric acid and its derivatives

Mise en evidence du passage par un complexe pentacoordine, (R3SnX,solvant) dans la reaction de substitution de l'halogene par un magnesien

Abstract The halogenotriphenyltinHMPT complex is more reactive toward a Grignard reagent than the halogenotriphenyltin itself. A mechanism is discussed for substitution reaction with saturated and unsaturated alkyl- and aryl-magnesium bromides.