Recyclable Magnetic MOF-Catalyzed Synthesis of 1-Aminoisoquinolines and 6-Aminophenanthridines from 5-(2-Bromoaryl)tetrazoles and 1,3-Diketones under Microwave Irradiation.

In this study, 5-(2-bromoaryl)tetrazoles were reacted with 1,3-diketones in DMF in the presence of a catalytic amount of magnetic Cu-MOF-74 (FeO@SiO@Cu-MOF-74) and a base under microwave irradiation to yield the corresponding 1-aminoisoquinolines. The FeO@SiO@Cu-MOF-74 catalyst could be easily recovered from the reaction mixture and reused four times without any significant loss of catalytic activity. An initial copper-catalyzed C(sp)-C(sp) bond formation accompanied by -Claisen deacylative cyclocondensation (for acyclic 1,3-diketones) and direct cyclocondensation (for cyclohexane-1,3-diones) is proposed as a key reaction pathway for this process.

Recyclable Magnetic Cu-MOF-74-Catalyzed C(sp)-N Coupling and Cyclization under Microwave Irradiation: Synthesis of Imidazo[1,2-]quinazolines and Their Analogues.

Magnetic Cu-MOF-74 (FeO@SiO@Cu-MOF-74) was synthesized for the first time by grafting MOF-74 (copper as the metal center) on the surface of core-shell magnetic carboxyl-functionalized silica gel (FeO@SiO-COOH), which was prepared by coating core FeO nanoparticles with hydrolyzed 2-(3-(triethoxysilyl)propyl)succinic anhydride and tetraethyl orthosilicate. The structure of FeO@SiO@Cu-MOF-74 nanoparticles was characterized by Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM). The prepared FeO@SiO@Cu-MOF-74 nanoparticles could be applied as a recyclable catalyst to the synthesis of N-fused hybrid scaffolds.

Synthesis of Imidazo[1,2-]phenanthridines by Recyclable Magnetic MOF-Catalyzed Coupling and Cyclization of 2-(2-Bromoaryl)imidazoles with Cyclohexane-1,3-diones Followed by Aromatization.

2-(2-Bromoaryl)imidazoles react with cyclohexane-1,3-diones in the presence of a catalytic amount of recyclable FeO@SiO@MOF-199 and a base to give the corresponding C-C coupled and cyclized products 6,7-dihydroimidazo[1,2-]phenanthridin-8(5)-ones in high yields. The magnetic MOF catalyst could be easily recovered and reused four times without any significant loss of catalytic activity. The coupled and cyclized scaffolds were aromatized to imidazo[1,2-]phenanthridines in high yields by a one-pot sequential procedure including reduction, dehydration, and oxidation.