Jean-Paul Quintard

Quelques aspects de la reactivite de l'α-chloro α-ethoxymethyltributyletain : etherification reductrice des aldehydes aromatiques et mise en evidence de formyltributyletain lors de la reaction d'hydrolyse

Abstract α-Chloro-α-ethoxymethyltributyltin reacts with aromatic aldehydes and leads to benzyl ethyl ethers with formation of tributyltin chloride and carbon monoxide. Analogously the formation of ethoxymethyltributyltin and tributyltin chloride on hydrolysis of this new organometallic reagent is explained by a process involving formyltributyltin as an unstable intermediate. This explanation is supported by the observation of an electronic spectrum between 350 and 450 nm during the hydrolysis.

New organotin synthons providing α-alkoxyorganolithium reagents

Abstract Diethoxymethyltributyltin was obtained in high yield from the reaction of tributylstannylmagnesium chloride with diethylphenylorthoformate. It reacted readily with acetyl chloride to give chloroethoxymethyltributyltin, which was easily transformed to ethoxymethyltributyltin by reduction with tributyltin hydride. Diethoxymethyltributyltin, a masked aldehyde anionic equivalent, was metallated with butyllithium, and the resulting new organolithium reagent was trapped with benzyl bromide, benzaldehyde, and cyclohexenone.

Interet de la deuteriation des molecules organostanniques en RMN de 119Sn : II. Relation de type karplus pour 3J(SnD) et stereochimie de deuteriostannation de quelques hydrocarbures ethyleniques

Abstract Whenever selective deuterium labelling is easily performed a new proficiency is given to FT 119 Sn NMR by the determination of the angular dependence of 3 J (SnD). Using model molecules with structures being checked by other methods, the angular dependence of 3 J (SnD) has been shown to follow a Karplus-like relationship. Illustrative examples for the qualitative and quantitative analysis of diastereoisomeric organotin compounds are described. This method allows for instance, a fast and convenient determination of the stereochemistry of alkene deutero- and hydro-stannations.

Préparation d'aminométhyltributylétains par stannylation de sels d'immonium au moyen du chlorure de tributylstannylmagnésium. Applications à la synthèse de β-aminoalcools

Abstract Tributylstannylmagnesium chloride reacts with immonium salts and gives non-substituted, α-substituted or α,α-disubstituted aminomethyltributyltins. The reaction, which can be extended to stannylation by tributylstannylalkalis, is not affected by the nature of the anionic part of the immonium salt. Transmetallation of aminomethyltributyltins with butyllithium, followed by condensation with carbonyl compounds, provides a regiospecific route to β-aminoalcohols.

Vibrational spectra of styrene and its seven deuterated vinylic isotopomers: Complete assignment of the spectra by valence force field calculations

Abstract Vibrational spectra of styrene and its seven deuterated vinylic isotopomers have been recorded. A normal coordinate calculation by a valence force field treatment has permitted a complete assignment of all bands observed for the eight molecules. These calculations have been applied to previously published data on phenyldeuterated styrenes and results are in fairly good agreement with experimental.

Interet de la deuteriation des molecules organostanniques en rmn de 119Sn : I. Acces aux constantes de couplage nJ(SnD) et application a l'etude structurale de vinyl et d'allyletains☆

Abstract The selective deuteration of organotin compounds gives FT 119 Sn NMR a new proficiency, since it allows direct access to n J (SnD) coupling constants. Usually n J (SnD) is easily apparent for n  1, 2, 3 and sometimes 4 (allyltin compounds). This criterion has been successfully applied for qualitative and subsequently quantitative analysis of vinyltin and allyltin compounds. In the first series, the stereochemistry of alkyne deuterostannation has been easily explored, the assignments of configurations being made directly from 3 J (SnD) on the basis of 3 J (SnD) trans > 3 J (SnD) cis . In the second series, the method appears to be the best tool for simultaneous study of regiochemistry and stereochemistry in the substitution of 3-deutero-5-methyl-2-cyclohexenyl toluene sulphonates by trialkylstannyl anions. The choice between regioisomers was made on the basis of 2 J (SnD) >- 4 J (SnD). A further aspect of this work is the observation of isotopic effects on 119 Sn chemical shifts which were tentatively rationalized considering inductive, steric or hyperconjugative contribution of deuterium.

Metallation des halogenures d'aryle par le tributylstannyllithium dans le tetrahydrofuranne

Abstract The metallation of aryl halides with tributylstannyllithium in THF proceeds via at least three different mechanisms whose relative rates depend on the nature of the halogen, the substrate and the experimental conditions. In the case of aryl bromides, a halogenmetal exchange (major process) is competing with a radical mechanism. With aryl chlorides, an arynic process, a halogenmetal exchange and a radical mechanism are involved. Finally, with aryl fluorides, the arynic process is usual, but it may be strongly competed by a radical mechanism whenever suitable experimental conditions are arranged.

Stereochimie de la reduction de cetones acycliques par l'hydrure de tributyletain

Abstract The stereochemistry of reduction of acyclic ketones with tributyltin hydride under ionic or flee-radical conditions has been established. The results are discussed using the usual models of asymmetric induction. The stereochemistry of the products is little affected by the hydrostannation mechanism and the stereoselectivity in both cases is minor.

Réactions d'hydrures de triorganoétain avec des systémes conjugués III. Cas des esters et nitriles α-acétyléniques en présence de méthanol

Abstract The reduction of the triple bond of α-acetylenic esters and nitriles by tributyltin hydride in methanol is described; the stereochemistry and reaction mechanisms are investigated. The addition of methanol to the triple bonds of α-acetylenic esters which constitutes a side reaction, has also been studied, and in particular the effect of methoxytributyltin, the stereochemistry and reaction mechanisms.

α-Ethoxybutenyltributyletains precurseurs d'α-ethoxybutenyllithiums: Application a la synthese d'enones via les monoethers homoallyliques d'α-glycols

Abstract α-Ethoxybutenyl)tributyltins are obtained from the reaction of appropriate allylic Grignard reagents with (α-chloro-α-ethoxymethyl)tributyltin, which is easily obtained from diethoxymethyltributyltin. Upon transmetallation (BuLi/THF/− 70°C), these new reagents afford α-ethoxybutenyllithiums, which when treated at − 70°C with allyl halides or carbonyl compounds give dihomoallyl ethers or homoallyl monoethers of α-glycols. The latter compounds upon acidic treatment afford α,β- or β,γ-enones, depending on the structure of the substrate and on the experimental conditions.