Metal-organic frameworks as efficient catalytic systems for the synthesis of 1,5-benzodiazepines from 1,2-phenylenediamine and ketones

Benzodiazepines and their derivatives are a very important class of nitrogen-containing heterocyclic compounds with biological activity that are widely used in medicine. In this study, we demonstrated synthesis of 1,5-benzodiazepines from 1,2-phenylenediamine and ketones (acetone, cyclohexanone, acetophenone, methyl ethyl ketone) in the presence of isostructural porous metal-benzenetricarboxylates of the families MIL-100(M) (M: V³⁺, Al³⁺, Fe³⁺ and Cr³⁺) and three porous aluminium trimesates Al-BTCs (MIL-96(Al), MIL-100(Al) and MIL-110(Al)). A combination of catalytic, theoretical and physicochemical methods showed that reaction rates and yields of 1,5-benzodiazepines were adjusted by the type of metal ions and accessibility of active sites. The yield of 1,5-benzodiazepines in the presence of MIL-100(M) was comparable with zeolites, such as HY, H-ZSM−5, β-zeolite and heulandite.