Gilles Dumartin

In situ generated, polymer-supported organotin hydrides as clean reducing agents

Abstract Polymer-supported organotin hydrides were generated in-situ from polymer-supported organotin halides and NaBH 4 . Their reducing ability was monitored by reaction with 1-bromoadamantane. The residual tin pollution was estimated by ICP-MS.

Catalytic and supported Barton–McCombie deoxygenation of secondary alcohols: a clean reaction

Abstract Secondary alcohols were deoxygenated using a new version of the Barton–McCombie process involving a catalytic amount of supported tin hydride in the presence of trimethoxysilane. The products are then easily separated from the catalyst by a simple filtration avoiding pollution by toxic tin by-products.

Un nouvel hydrure organostannique greffé sur support insoluble

Abstract A polystyrene-supported tin hydride was prepared from Amberlite XE305. The stannyl group was separated from the aromatic ring of polystyrene by four methylene units. The product contains 1.2 mmol active SnH/g polymer.

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.

Chemo, regio and stereoselectivity in the reaction of p-bromobenzaldehyde with α-ethoxycrotyltributyltin

Abstract The reaction of p-bromobenzaldehyde (1) with α-ethoxycrotyltributyltin (2) has proved amenable to control in terms of chemo, regio and stereochemistry, using appropriate experimental conditions, namely Pd(PPh 3 ) 4 catalysis, BF 3 .Et 2 O catalysis or simple heating. In the latter case, a dramatic kinetic effect has been observed: 2E has been proved to be much more reactive (and much more stereoselective) than 2Z .

Hydrostannation du bicyclo[3.1.0]hexene-2: Synthese et identification des methyl-4 et methyl-5 trimethylstannyl-3 cyclopentenes diastereoisomeres

Abstract 4-Methyl- and 5-methyl-3-trimethylstannylcyclopentenes were obtained from bicyclo[3.1.0]hex-2-ene through hydrostannation. The four isomers were identified by chemical and physicochemical methods such as 90 MHz 1H FT NMR spectroscopy which gives some conformational information in the series of 5-methyl-3-trimethylstannylcyclopentenes.

Stereochimie de la stannylation d'halogenures allyliques en serie cyclohexenique

Abstract cis - and trans -5-Methyl-2-cyclohexenyl chlorides were matallated by trimethylstannyllithium and tributylstannyllithium giving the corresponding allyltin compunds with inversion of configuration as shown by 13 C and 119 Sn NMR spectroscopy.

Metallation des chlorosilanes par les trialkylstannylanions

Abstract The stereochemistry of chlorosilane metallation by stannyl anions of the silacyclopentane series has been studied. Poor stereoselectivity is often observed for this reaction and the expected stannylsilanes are usually contaminated with products of side reactions. Concerning the mechanisms implied in the stannylation reaction, we consider that a reasonable interpretation of the experimental facts is the possibility of two competing processes: nucleophilic SN2 substitution (inversion at Si) and halogen-metal exchange (which implies retention or epimerization at the Si atom).

n J(SnD) Coupling constants: a powerful tool for structural analysis of organotin compounds by 119Sn fourier transform n.m.r. spectroscopy

n J(SnD) coupling constants, very easily deduced from the triplets observed by 119Sn Fourier transform n.m.r. spectroscopy with proton decoupling, may be used for the direct identification of isomeric or diastereoisomeric organotin compounds.