Synthesis and antioxidant activity of a novel series of pyrazolotriazine, coumarin, oxoazinone, and pyrazinopyrimidine derivatives.

A series of pyrazolotriazone derivatives 8-10 were obtained via coupling of 3-(3,5-dimethyl-1H-pyrazol-1-yl)-3-oxopropanenitrile (1) with 3-pyrazole diazonium chlorides 2-4, followed by heating of the formed hydrazones 5-7 in acetic acid, respectively. Moreover, coupling reaction of 1 with the aryl diazonium salts 15a-c afforded hydrazones 16a-c. Furthermore, treatment of 1 with 2-hydroxy-1-aldehydes 18-20 afforded the corresponding coumarins 21-23, respectively. Finally, compound 1 reacted with 1-nitrosonaphthalen-2-ol (26) and 6-amino-5-nitroso-2-thioxo-2,3-dihydropyrimidin-4(1H)-one (28) to give 3-oxo-3H-naphtho[2,1-b][1,4]oxazine-2-carbonitrile (25) and pyridazinopyrimidine (29), respectively. The newly synthesized compounds were screened for their ABTS antioxidant activity. Compounds 7 (90.39%), 10 (85.88%), and 16a (91.95%) exhibited promising activities. The most potent compound, 16a, has the ability to protect DNA from the damage induced by bleomycin.