As an analogue of pyridazino-fused ring systems with pharmacological activities, the novel pyridazinol[3,4-b][1,5]diazepine ring system was prepared. The synthetic pathway includes three steps from 4 5-(N-benzyl-N-3-hydroxypropyl)amino derivative which is easily available through nucleophilic substitution reaction of the known 4,5-dichloro-2-methyl-6-nitro-3(2H)-pyridazinone (2) with N-benzyl-N-(3-hydroxypropyl)amine. In the first step, compound 4 was treated with thionyl chloride to give the chloropropyl derivative 5. In the second step, a Bechamp reduction was carried out with Fe in acetic acid to obtain the amino compound 6, and finally the ring closure reaction of 6 was performed in N,N-dimethylformamide in the presence of potassium carbonate at 110 degrees C for 40 hours. In this way the bicyclic compound 7 could be isolated in 48% yield.