The microwave irradiation of a series of 2-diazo-1,3-diketones in the presence of an o-phenylenediamine derivative triggered a domino Wolff rearrangement/nucleophilic addition/intramolecular imination sequence to provide a new synthetic entry to 1,3-dihydr-2H-1,5-benzodiazepin-2-ones, a class of molecules with important biological properties.