Studies on alkylheterocycles. I. A convenient Synthesis of Phthalazines

Ethyl‐2‐arylhydrazono‐2,3‐dioxobutyrate 1a, b reacted with ethylcyanoacetate to yield the pyridazino derivatives 2a, b. Similarly, the pyridazine 2c was obtained via reaction of 3‐arylhydrazonopentan‐2,3,4‐trione with the same reagent. The phthalazines 6 were obtained upon reaction of 2a–c with ylidenemalonitrile 3a, b. The styrene derivatives 7a–d were isolated from the reaction of 2a–c with the appropriate aromatic aldehyde. Compounds 7a–d were subsequently utilized for the synthesis of 6a, d–f respectively via reaction with malononitrile. On the other hand, the phthalazine derivative 8 was formed upon reaction of 2a with either ethylcyanoacetate or malononitrile.