Development of Novel Synthetic Methods Based on Selective Oxidation of Organometallics

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One-electron oxidation or reduction of organometallics by one-electron redox with transition metals permits a novel reaction behavior based on the change of the electronic state on metals, which is considered to provide novel synthetic reactions. If transmetallation is taken place instead, the reactivities based on the characteristics of the introduced metals are expected to widen the scope of stnthetic methods via organometallic intermediates. Oxovanadium compounds with one-electron oxidation capability are employed for this purpose in this research project. The oxidative transformations of organometallics have been investigated to provide versatile methods for selective carbon-carbon bond formation.1) Organoaluminum ate complexes obtained by treatment of alkenylaluminums with alkyllithiums underwent oxidative coupling with oxovanadium oxidant to afford the corresponding enynes selectively. This reaction was found to be applied to a variety of organoaluminum compounds.2) The similar oxidative coupling reaction proceeded well starting from arylaluminums in stead of alkenyl ones.3) The direct oxidation of aryldialkylaluminums with oxovanadium compounds led to the introduction of an alkyl group to give the alkyl-substituted arenes. The steric bulkiness and redox potentials of oxovanadium compounds reflected on the oxidative coupling. The one-pot transformations are possible without isolation of the intermediate complexes and considered to be of synthetically potetial. The redox interaction between organometallics and oxovanadium compounds is likely to permit these transformations. The coupling is recognized to be formal reductive elimination of main-group organometallics, which has been less accessible by conventional methods.