A series of 3,4-dihydro-2-pyronyl-1,5-benzodiazepines 4 was prepared by the reaction of DHA (dehydroacetic acid), o-PDA (orthophenylenediamine) and aromatic aldehydes in the presence of a catalytic amount of TFA (trifluoroacetic acid). 2-Pyronyl-1,5-benzodiazepines 6 in turn were synthesised from DHA, o-PDA and acetal [dimethyl formamide-dimethyl acetal (DMF-DMA) or dimethyl acetamide-dimethyl acetal (DMA-DMA)] under basic catalysis.