Ring construction via pseudo-intramolecular hydrazonation using bifunctional δ-keto nitrile

An α-nitro-δ-keto nitrile efficiently reacted with hydrazines at room temperature, even in the absence of a catalyst, to afford the corresponding hydrazones; the reactions proceeded through a pseudo-intramolecular process. The hydrazone derived from hydrazine monohydrate underwent water-assisted cyclization, which yielded the corresponding diazepine. The hydrazones derived from 4-nitrophenylhydrazine and 2,4-dinitrophenylhydrazine were converted into pyridazines upon being heated in DMSO.