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 MnCl2 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 1H-NMR, which identified the key role of tris-coordinated ate-iron(II) species in the catalytic process.
Highlights
Transition-metal catalyzed cross-couplings are widely used in the development and production of pharmaceutical compounds [1]
In order to rationalize some of the mechanistic features of the transformations reported first section, we focused our efforts on the coupling system involving various bis-(aryl)manganese first section, we focused our efforts on the coupling system involving various bis-(aryl)manganese nucleophiles and bis-phenylmanganese)
This choice has been motivated by the low cross-coupling yields obtained with this electrophile first section, we focused our efforts on coupling system involving various bis-(aryl)manganese nucleophiles
Summary
Transition-metal catalyzed cross-couplings are widely used in the development and production of pharmaceutical compounds [1]. We wish to report an effective one-pot preparation of those functionalized bis-(aryl)manganese reagents (Ar2 Mn2MgX2 4LiCl, denoted as Ar2 Mn (1), Scheme 1) starting from aryl bromides, which are followed by an iron-catalyzed cross-coupling of 1 with alkenyl iodides and bromides, and provide a range of polyfunctionalized alkenes (4, Scheme 1). These bis-(aryl)manganese reagents are generally stable at RT (25 ◦ C) for several hours, which makes them suitable reagents for mild cross-coupling reactions [32]. One-pot preparation of bis-(aryl)manganese reagents by in situ trans-metalation followed by iron-catalyzed cross-couplings alkenyl iodides and bromides.
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