A Novel Synthesis of Some 1,4-Phenylene-bis-heterocyclic Derivatives and of Some Pyran, Pyrano[2,3-c]pyrazole, and Pyrano[2,3-d]pyrimidine Derivatives [1]

摘要

p-Diacetyl benzene 1 undergoes bromination to afford p-bromoacetyl phenacyl bromide 2. Compound 2 reacts with twofold excess of malononitrile to afford 2-{2-[4-(3,3-Dicyanopropionyl)-phenyl]-2-oxo-ethyl}-malononitrile 3. Compound 3 could be cyclized to afford the 1,4-phenylene-bis-furan derivative 4. Compound 3 reacts also with a twofold excess of hydrazine hydrate and phenyl hydrazine under dry conditions at RT to afford the bis-pyrazole derivatives 5a, b, respectively. The reaction of 5a, b with the same reagents in refluxing dioxane afforded the bis-pyrazolopyridazine derivatives 7a, b, respectively. The azo coupling of compound 3 with arene diazonium salts afforded the bis-pyrazole derivatives 9a-c. The beta-keto esters 10a, b react with benzaldehyde and malononitrile in a one pot synthesis to afford the pyran derivatives 11a, b. These latter compounds react with hydrazine hydrate and urea derivatives to afford the pyrano[2,3-c] pyrazoles 15a, b and the pyrano[2,3-d] pyrimidine derivatives 17a, b, respectively.