Development of Novel Oxidative Transformation Based on Heterometallic Electron Transfer

点击翻译按钮获取中文摘要

One-electron oxidation of main-group 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 takes place instead, the reactivities based on the characteristics of the introduced metals are expected to widen the scope of synthetic 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) Oxovanadium (V) compounds like VO (OEt) Cl_2 serve as useful oxidants for organozinc compounds, providing the corresponding cross-coupling products derived from two ligands of organozinc compounds. In particular, triorganozincates undergo selective cross-coupling smoothly by the action of oxovanadium (V).2) VO (OEt) Cl_2 induces oxidative ligand coupling of aryltrimethylzincates, prepared from bromoarenes and Me_4ZnLi_2, giving the corresponding methylarenes.3) Oxovanadium (V) compounds induce nucleophilic α, β-vicinal dialkylation of cyclic α, β-enones with dialkylzinc reagents. Alkylzinc enolates, generated from cyclic enones and lithium trialkylzincates, are oxidized by VO (OEt) Cl_2, giving 2, 3-dialkylcycloalkanones. The one-pot transformation is possible without isolation of the intermediate complexes and considered to be of synthetically potetial.The redox interaction between main-group organometallics and oxovanadium compounds is demonstrated to permit these transformations. The coupling is recognized to be formal reductive elimination of the organometallics, which has been less accessible by conventional methods.