A catalyst-free four-component domino reaction for the synthesis of functionalized 3-acyl-1,5-benzodiazepines

Various functional 3-acyl-1,5-benzodiazepines containing carboxyl, ester and acyl groups at the 2-position were synthesized via an efficient, sustainable and catalyst-free domino reaction. During the synthesis process, one new cycle and four new bonds (one C–C, two C–N and one CC) were constructed by the nucleophilic substitution, nucleophilic addition, dehydration and cyclization reaction by the H+ shift. Furthermore, a total of 26 examples were examined by reacting inexpensive starting materials of N,N-dimethylformamide dimethyl acetal, aromatic ketones, 1,2-phenylenediamine compounds and aldehyde derivatives. Therefore, it displayed a broad substrate scope, good functional group tolerance, high yields (77–97%) and the ease of obtaining target compounds without the involvement of toxic solvents and column chromatography, which provided a novel method for the synthesis of a wide variety of biologically relevant 1,5-benzodiazepines.