Regioselective Oxidative Bromination of Arenes by Metal-Organic Framework Confined Mono-Bipyridyl Iron(III) Catalyst

Abstract

Oxidative bromination of arenes is an effective and environmentally friendly method for synthesizing bromoarenes. We have developed a highly robust zirconium-metal-organic framework (MOF)-supported mono bipyridyl-iron(III) chloride catalyst (bpy-UiO-FeCl3) for oxidative bromination of arenes using H2O2 as the oxidant and KBr as the bromine source. The bpy-UiO-FeCl3 catalyst exhibits high conversion rates for various substituted arenes, yielding significant amounts of bromoarenes with excellent regioselectivity, and recyclability under mild reaction conditions. The MOF-catalyst outperforms its homogeneous counterparts in terms of both activity and regioselectivity due to the stabilization of the mononuclear bipyridyl-iron(III) species within the active sites in the MOF's pores. Furthermore, the confinement of these active sites within the robust, well-defined, and uniform porous framework enhances the regioselectivity of the bromination through shape-selective catalysis. The mechanism of bpy-UiO-FeCl3 catalyzed oxidative bromination of arenes was thoroughly investigated by a combination of control experiments, spectroscopic analyses, and computational studies. These findings underscore the importance of MOFs in the development of heterogeneous catalysts based on earth-abundant metals for the sustainable synthesis of haloarenes.