Iron-Catalyzed Cross-Coupling of Bis-(aryl)manganese Nucleophiles with Alkenyl Halides: Optimization and Mechanistic Investigations

Abstract : Various substituted $bis$-(aryl)manganese species were prepared from aryl bromides by one-pot insertion of magnesium turnings in the presence of LiCl and in situ trans-metalation with MnCl$_2$ in THF at −5°C within 2 h. These $bis$-(aryl)manganese reagents undergo smooth iron-catalyzed cross-couplings using 10 mol% Fe(acac)$_3$ with various functionalized alkenyl iodides and bromides in 1 h at 25°C. The aryl-alkenyl cross-coupling reaction mechanism was thoroughly investigated through paramagnetic $^1$H-NMR, which identified the key role of $tris$-coordinated $ate$-iron(II) species in the catalytic process.