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‐1 H ‐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(1 H )‐one ( 28 ) to give 3‐oxo‐3 H ‐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.