Synthesis of Novel 5,6-dihydro-4H-[1,2,4]triazolo[4,3-a][1,5]benzodiazepines

The series new fused tricyclic [1,2,4]triazolo[4,3-a][1,5]benzodiazepines have been synthesized by condensation-cyclization reaction of 1,5-benzodiazepine hydrazine derivatives as starting materials and triethyl orthoformate or triethyl orthoacetate. After screening various solvents like ethanol, isopropanol, xylene, we have found that xylene was the best choice for this reaction, because the reaction proceeds well in high boiling solvent. The 1,5-benzodiazepine hydrazines with electron-releasing methyl group gave a products in a poorer yield after a longer period of time, whereas compounds with electron-withdrawing group afforded a better yield of corresponding triazoles. The structure of the cycloadducts has been assigned by means of IR, 1H and 13C NMR spectroscopic measurements