Réaction de dérivés à liaison germanium-azote (germylamines, cyclogermazanes et germa-imines transitoires) avec la di-t-butyl-3,5-orthoquinone

Abstract

Several germanium-nitrogen compounds were treated with 3,5-di-t-butylorthoquinone ( 1). In the case of the germylamines R 3GeNMe 2 (R = Et, Ph), 1,2 and 1,4 adducts were formed, as shown by 1H NMR spectroscopy. The thermally unstable 1,4 adduct, decomposes with nitrene elimination to give 2,2-dialkyl or 2,2-diaryl (6,8-di-t-butyl)-4,5-benzo-2-germa-1,3-dioxolane. The 1,2 adduct, through intermolecular redistribution, leads to digermyloxide (R 3Ge) 2O and a gem-diamine with partial regeneration of the starting quinone 1. These addition reactions proceed through a monoelectronic transfer mechanism, with formation of a transient o-semiquinonic radical identified by ESR spectroscopy. This transient radical leads to O-germyl 3,5-di-t-butylcatechol by hydrogen abstraction from the solvent. The proposed mechanism explains the formation of the germylated compounds as well as the organic by-products. Similar reactions were observed between cyclodigermazanes and 1. The 1,4 cycloaddition generates germadioxolanes with nitrene expulsion, whereas the 1,2-cycloaddition leads to the germoxane and conjugated ketoimine, or diimine. The latter is a good trapping agent for the nitrene formed in the decomposition of the 1,4 adduct. Both the 1,4 and 1,2 cycloadduct decompositions imply transient germaimine formation. The same germaimine, formed at room temperature from intramolecular dehydrohalogenation of the hindered R 2ClGeNHR′ by 1,8-diaza[5.4.0]bicyclo-7-undecene) gives the same reaction products.