Synthesis of Binuclear Isoquinoline- and Pyridine-Fused Benzimidazole-4,7-diones by Magnetic MOF-199-Catalyzed C–C Coupling/Cyclization Followed by Oxidation

2-(2-bromoaryl)-4,7-dimethoxy-1H-benzo[d]imidazoles and (Z)-2-(2-bromovinyl)-4,7-dimethoxy-1H-benzo[d]imidazoles react with 1,3-diketones by microwave irradiation in DMF in the presence of a catalytic amount of recyclable Fe₃O₄@SiO₂@MOF-199 along with a base to give binuclear isoquinoline- and pyridine-fused benzimidazoles, respectively. Treatment of such binuclear N-fused hybrid scaffolds with ceric ammonium nitrate in acetonitrile/H₂O or HBr/FeCl₃ in H₂O affords binuclear isoquinoline- and pyridine-fused benzimidazole-4,7-diones in good to high yields.