Nouveaux oxamétallocycloalcanes (VII) Synthèse de (germa‐, sila‐, et stanna‐)dioxacycloalcanes et alcènes par insertion de dérivés carbonylés sur la liaison métal‐oxygène d'éthers cycliques organométalliques

Abstract

The insertion reactions of carbonyl derivatives such as acetaldehyde, chloral, hexachloro‐ and hexafluoro‐acetone on the metal‐oxygen bond of alkoxy‐organometallic compounds have been studied in the case of numerous cyclic ethers containing silicon, germanium or tin atoms in the ring.These reactions proceed by ring expansion leading to the formation of cyclic acetals: germaoxetanes yield 4‐germa‐1,3‐dioxanes, (sila‐, germa‐ or stanna‐) oxacyclopentanes give 1,3‐dioxacycloheptanes and (germa‐ or stanna‐) oxacyclopentenes lead to 1,3‐dioxacycloheptenes with the group IV element in position 4.The mechanism of these insertion reactions is discussed according to the nature of carbonyl derivatives and metal heteroatom in the starting cyclic compounds, as well as catalytic and solvent effects.