Regioselective ring opening of styrene oxide by carbon nucleophiles catalyzed by metal–organic frameworks under solvent-free conditions

Abstract

In the present study, the regioselective ring opening of styrene oxide by indole, aniline, imidazole, pyrrole and benzimidazole as carbon nucleophiles in the presence of Fe(BTC) (BTC: 1,3,5-benzenetricarboxylate)and Cu3(BTC)2 as heterogeneous solid acid catalysts under solvent-free conditions under mild reaction conditions is reported. Furthermore, Fe(BTC) and Cu3(BTC)2 exhibited higher activity under solvent-free conditions than in the presence of solvents. Control experiments with the corresponding homogeneous catalysts reveal the positive role played by the Lewis acids in these MOFs. On the other hand, the activity of these catalysts is significantly reduced in the presence of pyridine, thus, suggesting the involvement of Lewis acid sites. Both Fe(BTC) and Cu3(BTC)2 MOFs show high regioselectivity in the ring opening of styrene oxide by indole. Fe(BTC) and Cu3(BTC)2 are used for four cycles without significant decay in its activity. In addition, comparison of the fresh and four times used Cu3(BTC)2 catalysts by powder XRD and FT-IR indicate the stability of these catalysts under the present experimental conditions. A suitable mechanism is also proposed based on the observed catalytic data.