RESUMEN
Magnetic Cu-MOF-74 (Fe3O4@SiO2@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 (Fe3O4@SiO2-COOH), which was prepared by coating core Fe3O4 nanoparticles with hydrolyzed 2-(3-(triethoxysilyl)propyl)succinic anhydride and tetraethyl orthosilicate. The structure of Fe3O4@SiO2@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 Fe3O4@SiO2@Cu-MOF-74 nanoparticles could be applied as a recyclable catalyst to the synthesis of N-fused hybrid scaffolds. 2-(2-Bromoaryl)imidazoles and 2-(2-bromovinyl)imidazoles were coupled and cyclized with cyanamide in DMF in the presence of a catalytic amount of Fe3O4@SiO2@Cu-MOF-74 along with a base to give imidazo[1,2-c]quinazolines and imidazo[1,2-c]pyrimidines, respectively, in good yields. The Fe3O4@SiO2@Cu-MOF-74 catalyst could be easily recovered by a super magnetic bar and recycled more than four times while almost maintaining catalytic activity.
RESUMEN
2-(2-Bromoaryl)imidazoles react with cyclohexane-1,3-diones in the presence of a catalytic amount of recyclable Fe3O4@SiO2@MOF-199 and a base to give the corresponding C-C coupled and cyclized products 6,7-dihydroimidazo[1,2-f]phenanthridin-8(5H)-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-f]phenanthridines in high yields by a one-pot sequential procedure including reduction, dehydration, and oxidation. The present protocol could be applied to the synthesis of Zephycandidine A, which is known to exhibit anti-tumor activity.
RESUMEN
Aryl 2-bromobenzoates and aryl 2-bromocyclohex-1-enecarboxylates are cyclized by microwave irradiation in dimethylformamide in the presence of K2CO3 to give the corresponding 6 H-benzo[ c]chromen-6-ones and their 7,8,9,10-tetrahydro analogues, respectively, in 50-72% yields. Aryl 3-bromoacrylates are also converted into 2 H-chromen-2-ones under the employed conditions.
RESUMEN
2-(2-Bromovinyl)- and 2-(2-bromoaryl)-benzimidazoles, including their 4,7-dimethoxy analogs, react with primary amides by microwave irradiation (or usual heating) in dimethylformamide in the presence of a catalytic amount of CuI along with a base to give the corresponding benzo[4,5]imidazo[1,2-c]-pyrimidines and -quinazolines in good yields. Treatment of benzo[4,5]imidazo[1,2-c]-pyrimidines and -quinazolines having methoxy group on benzimidazole moiety with aqueous ceric ammonium nitrate affords unprecedented N-fused hybrid scaffolds, benzo[4,5]imidazo[1,2-c]-pyrimidin-6,9-diones and -quinazoline-8,11-diones, respectively, in high yields.
RESUMEN
Quinolin-2(1H)-ones and phenanthridin-6(5H)-ones are synthesized in high yields by K2CO3-promoted cyclization of N-aryl-ß-bromo-α,ß-unsaturated amides and N-aryl-2-bromobenzamides in dimethylformamide under microwave irradiation.
RESUMEN
2-(2-Bromovinyl)benzimidazoles and 2-(2-bromophenyl)benzimidazoles react with cyanamide by microwave irradiation in dimethylformamide in the presence of a catalytic amount of CuI along with a base to give the corresponding benzo[4,5]imidazo[1,2-c]pyrimidin-1-amines and benzo[4,5]imidazo[1,2-c]quinazolin-6-amines, respectively, in moderate to good yields. 2-(2-Bromophenyl)indoles also react with cyanamide under similar conditions to afford indolo[1,2-c]quinazolin-6-amines. The reaction pathway seems to proceed via a sequence such as intermolecular C-N coupling, C-N formative cyclization, and tautomerization.
