M. Joly

Sultones organométalliques : IV. Réactions de sulfonation en série silacyclobutanique

Abstract The behaviour of some substituted silacyclobutanes with respect to sulfur trioxide and other sulfonating agents (SO 3 /dioxane, trimethylsilyl chlorosulfonate) is studied. The 1,1-dialkylated derivatives of silacyclobutane, 2-methylsilacyclobutane and 3-methylsilacyclobutane as well as the spiranes of the type (CH 2 ) n Si(CH 2 ) 3 ( n = 4 or 5) react with sulfur trioxide to give 4-sila-1,4-butanesultones. On the other hand, the alkoxylated or dialkylaminated derivatives fix SO 3 via the functional group, thus giving silacyclobutanyl sulfates or amidosulfates of the type XSO 2 O(R)Si(CH 2 ) 3 (X = OR′, NR′ 2 ). The sulfonation of 1-methyl-1-phenylsilacyclobutane leads mainly to 1-methyl-1-silacyclobutylbenzenesulfonate, besides the expected sultone. The structure of the insertion products of SO 3 in the SiC, SiN, SiO and SiCl bonds is deduced from their infrared and protonic resonance spectra. Reaction mechanisms, permitting to ascertain the role of the substituents on the mode of insertion of sulfur trioxide and the reactivity of the cyclobutane SiC bond, are considered.

Stereochemistry of reactions in the 1,2-dimethylsilacyclopentane ring system. II. Stereoselective transformation

Abstract Preparations, separations of geometric isomers, and structural assignments based on nmr and on chemical evidence are described for a number of 1-substituted 1,2-dimethylsilacyclopentanes. A number of stereospecific reactions have been observed, and the stereochemistry is in all cases the same as that observed for acyclic silanes. A discussion of the role of ring strain in determining stereochemical outcome and reaction rates is presented.

Nouveaux cyclogermanes a isomere geometrique preferentiel, les dimethyl-1,2 germacyclopentanes: synthese des precurseurs

Abstract Several 2-methylgermacyclopentanes have been obtained from 1,4-dibromopentane and germanium halides by the Grignard procedure. The synthesis of 1,2-dimethylgermacyclopentane is realized in good yields in five steps from diphenyldibromogermane; the configurationally stable geometric isomers can be separated by chromatography or spinning band distillation. Attempts for stereospecific synthesis of 1,2-dimethyl-1-halogenogermacyclopentanes are also reported. The proposed configurations are supported by 1 H and 13 C NMR data.

Sultones et sultines organometalliques VII. Reactions d'insertion de l'anhydride sulfureux dans la liaison silicium-carbone: Sultines organosiliciques

Abstract The behaviour of some substituted silacyclobutanes with respect to sulfur dioxide is studied. The alkylated, arylated and alkoxylated derivatives of silacyclobutane react with SO 2 to give the first “silasultines” (2-oxo-4-sila-1,2-oxathianes). The structure and the configurational analysis of the insertion products are proved by chemical and physicochemical ways. The mechanism of the SO 2 insertion is discussed.

Nouveaux cyclogermanes a isomere geometrique preferentiel: synthese de dimethyl-1,2 germacyclopentanes fonctionnels☆

Abstract 1,2-Dimethylalcoxy(amino or thio)germacyclopentanes with a preferential geometric isomer are obtained by stereoselective alcoholysis, aminolysis or thiolysis of 1,2-dimethyl-1-bromogermacyclopentane. They give highly stereospecific reactions with Grignard reagents leading to various derivatives of 1,2-dimethylgermacyclopentane having a preferential isomer. Hydrogermylation of alcenes and alcynes with 1,2-dimethylgermacyclopentane are also stereospecific reactions. The configurations of the products are established by 1H and 13C NMR spectroscopy.

Stereochimie de la sulfonation d'organosilanes

Abstract The stereochemical route for sulfonation reactions of organosilanes has been determined. The predominant inversion of configuration at silicon is observed in the reaction of sulfur trioxide with the geometric isomers of 1,2-dimethyl-1phenylsilacyclopentane. Although only one isomeric ratio of the 1,2-dimethyl1-alkoxy- (or amino-)-silacyclopentanes was available, the retention of configuration at silicon is presumably the stereochemistry for sulfonation of these alkoxy and aminosilanes. The reaction of sulfur trioxide with the 1,3-dimethyl-1-n-butylsilacyclobutane is essentially stereospecific, but this is not the case for alkoxy and amino compounds. A mechanistic interpretation is discussed in terms of the SE process.

Synthese de nouveaux composes permettant l'etude stereo- chimique des processus reactionnels au niveau de l'atome de germanium: les dimethyl-1,2 germacyclopentanes

Abstract The synthesis of 1,2-dimethylgermacyclopentane is described. The geometric isomers, configurationally stable, are readily separable by spinning band distillation, and their reaction with ethylene, acetylene and 1-hexene proceeds with retention of configuration at the germanium atom. The proposed configurations are supported by spectroscope data ( 1 H and 13 C NMR).

Etudes stereochimiques dans la serie du silacyclopentane: synthese de dimethyl-1,2 alcoxy-1 silacyclopentanes a stereoisomere preferentiel

Abstract The stereoselective alcoholysis of 1,2-dimethyl-1-chlorosilacyclopentane and the catalytic alcoholysis of 1,2-dimethylsilacyclopentane are described.

Stereochimie de la reaction de rupture par le brome de la liaision siliciumaryle du dimethyl-1,2 phenyl-1 silacyclopentane

Abstract Stereospecific synthesis of geometric isomers of 1,2-dimethyl-1-phenylsilacyclopentane is described. We demonstrate that brominolysis of the arylsilicon bond occurs with predominant inversion of configuration at the silicon atom of the silacyclopentane ring.