Etude comparative des réactions par transfers monoeĺectronique entre les germylamines primaires, secondaires et tertiaires et la 3,5-di-tert-butylorthoquinone

Abstract

Several germylamines were treated with 3,5-di-t-butylorthoquinone ( 1). Competitive 1,2 and 1,4 additions resulted using the tertiary amine Et 3GeNPh 2. The thermally unstable 1,4 adduct gives 2,2-dialkyl-4,5-(6,8-di-t-butyl)benzo-2-germa-1,3-dioxolanne. The 1,2 adduct leads via intermolecular redistribution to bis(triethylgermyl)oxide ((Et 3Ge) 2O), and aminal with partial regeneration of the initial quinone. These reactions seem to proceed solely via a mono-electron transfer mechanism; the aminyl radical Ph 2N . and the transitory o-semiquinonic germylated radical formed in the reaction have been characterized by ESR spectroscopy. The o-semiquinonic radical then gives O-germyl-3,5-di-t-butylcatechol by hydrogen abstraction. As ethylene and isobutene have been characterized, these hydrogen abstractions occur from ethyl groups linked to germanium and from t-butyl groups belonging to the organic moieties. In the reaction of the secondary amine Et 3GeN(H)Ph, a germylaminyl radical is mainly formed instead of an o-semiquinonic germylated radical, which can explain the lesser amount of germadioxolanne obtained. The quinone 1 is partially transformed in o-diphenol under the action of Mes 3GeNH 2. No germylated adducts are observed. Aminyl radicals characterized in several reactions between germylamines and 1 were also obtained via monoelectronic transfer between lithium amids and tri-t-butylnitrozobenzene (BNB), thus providing a new, useful method for obtaining such species. constitue une nouvelle bl]