Synthesis of Some Potentially Bioactive Compounds From Visnaginone

The reaction of 5-acetyl-6-hydroxy-4-methoxybenzo[b]furan (visnaginone Ia) with 2-diethylaminoethylchloride led to the formation of 5-acetyl-6-diethylamino-ethoxy-4-methoxybenzo[b]furan (II), whereas condensation of compound II with some aromatic aldehydes afforded the corresponding chalcones IIIa-c. Methylation of visnaginone (Ia) gave 5-acetyl-4,6-dimethoxybenzo[b]furan (Ib), which in turn reacted with some aromatic aldehydes to give the corresponding chalcones IIId,e. The reaction of chalcones IIId,e with hydrazine hydrate in alcohol gave the pyrazoline derivatives IVa,b, whereas when the same reaction was carried out in acetic acid it afforded the N-acetylpyrazoline derivatives Va,b. Similarly, the reaction of IIId,e with phenyl hydrazine in acetic acid led to the formation of phenylpyrazoline derivatives VIa,b, whereas condensation of chalcones IIId,e with hydroxyl amine hydrochloride gave the isoxazoline derivatives VIIa,b. The reaction of compound II with phenylhydrazine and 2,4,6-trichlorophenylhydrazine afforded the corresponding phenyl hydrazone derivatives VIIIa,b. Mannich bases IXa,b were synthesized by the reaction of visnaginone (Ia) with piperidine and benzylamine in the presence of formaline.