Zur Reaktion von ?Pyrazolonblau? mit Diazomethan

About the Reaction of „Pyrazolone Blue” with Diazomethane The reaction of “pyrazolone blue” with diazomethane was investigated. A pyridazinone derivative 3, a heterocyclic spiro-cyclopropyl product 4 and a compound 7, which contains three pyrazolone and two diazomethane entities, are formed. 3 reacts with an excess of diazomethane to the methoxy derivative 6. The spiro-cyclopropyl compound 4 is not stable and isomerizes to the corresponding 4,4′-methylidene-bispyrazolone 5. The structures of the products were established by spectroscopic methods and X-ray analysis.