Alfreda Faucher

Composes organometalliques a cycle moyen : VI. Mise en evidence d'une interaction transannulaire O—Si en serie silacyclanique par spectrometrie de masse et resonance magnetique nucleaire de 29Si

Abstract A mass spectral study of a series of silacyclanones with 9—13-membered rings revealed the existence of the ion C 2 H 7 OSi ( m/e 75) whose formation was interpreted as resulting from a transannular interaction between the carbonyl oxygen and silicon. The 29 Si NMR results were in good agreement with the existence of this interaction.

Thermal isomerization of 3-silabicyclo[3.1.0]hexanes: A new route to silacyclopentenes and silacyclohexenes

Abstract By thermolysis, 3-silabicyclo[3.1.0]hexanes lead to silacyclohexenes as major products and also to silacyclopentenes. The ratio of the different isomeric silicon rings is strongly dependent on the nature of the C(1) and C(5) substituents (R, R′ = H, Me).

Composés organométalliques à cycle moyen III. Synthèse du méthyl-1 germa-1 oxa-12 bicyclo [5.4.1] dodécane par cyclisation transannulaire

Summary Dehydrocondensation of 6-methyl-6-germacycloundecan-l-ol in the presence of Raney nickel leads to an oxagermabicyclododecane through a transannular process. This compound is also formed by intramolecular addition of 6-germacycloundecan-1-one in the presence of zinc dust. The structure of this bicyclic oxagerma derivative has been determined by chemical reactions (cleavage of the germanium-oxygen bond by LiAlH 4 and CH 3 -COCl) and spectroscopic methods (IF, NMR and mass spectrometry).

New series of functional bicyclic organogermanium compounds

Abstract 1,4-Addition of germanium diiodide to 3,4-bis(methylene) oxolane, thiolane and phenylazolidine, leads to new series of functional bicyclic germanium derivatives, potentially valuable synthons for other organogermanium compounds.

Medium-sized organometallic derivatives : IX. transannular nucleophilic substitution in organosilicon and organogermanium eleven-membered rings

Abstract Olahs reagent (HF-pyridine) reacts easily at room temperature with 6,6-dimethyl-6-sila-(and 6,6-dimethyl-6-germa-)-cycloundecanols. In each case, the principal product formed is not the expected cyclic organosilicon (or organogermanium) fluoride but the compound resulting from a transannular substitution reaction at the heteroatom with cleavage of one intracyclic heteroatom-carbon bond. The structures of the derivatives obtained were determined by 19 F NMR and, after methylation, by mass spectrometry, 1 H and 13 C NMR, and chemically.

Thia-6 diphényl-3,3 sila-3 (et germa-3)bicyclo[3.1.0]hexanes

Abstract 6-Thia-3,3-diphenyl-3-sila-(and 3-germa-)bicyclo[3.1.0]hexanes are prepared from the corresponding metallaoxiranes using triphenylphosphorus sulfide with trifluoroacetic acid as solvent. These thiiranes are unstable compared to the corresponding oxiranes. Partial desulfurization results from thermic or chemical processes leading to 1-metallacyclopent-3-enes. Cyclometallathianes are potential precursors of metallathiones and thiofunctional metallacyclopentanes.

Synthesis and characterization of poly([3,4,c]furano-1-germa-1,1-dimethylcyclopentane)

SummaryPoly([3,4,c]furano-1-germa-1,1-dimethylcyclopentane) (I) has been prepared by the anionic ring opening polymerization of 3-oxa-7,7-dimethyl-7-germabicyclo[3.3.0]- octa-1,4-diene (II) co-catalyzed byn-butyllithium and HMPA in THF. I has been characterized by1H,13C NMR, IR and UV spectroscopy as well as by elemental analysis. The molecular weight distribution of I has been determined by gel permeation chromatography (GPC), its thermal stability established by thermogravimetric analysis (TGA) and its glass transition temperature (Tg) measured by differential scanning calorimetry (DSC).

Composés organométalliques à cycle moyen—VIII. Interaction transannulaire p(O)-d(Si, Ge) dans des composés organométalliques à cycle moyen comportant une fonction cétone ou alcool. Etude en spectrographie infrarouge i.r.

Abstract The intensity of ν CO absorption band was determined for a number of carbon, sila- and germacyclanones. For medium-sized rings, the observed decrease of the intensity for the silicon derivative, and to a lesser extent for the germanium compound, can be explained by 2 p (O) →- 3 d (Si) or 4 d (Ge) transannular interaction between carbonyl oxygen and the hereratom. No interaction has been detected in the case of the corresponding sila- and germacyclanols.