Synthesis and anti-oxidant activity of novel pyrimido[4,5-b]quinolin-4-one derivatives with a new ring system

Reaction of 2-Hydrazino-derivative 6b with aliphatic acids yielded the triazolopyrido-pyrimidines 7a,b. Also, reaction of 6b with carbon disulfide or potassium thiocyanate afforded 10-mercapto/aminotriazolopyridopyrimidine (9,10), respectively. Compound 6b reacted with nitrous acid gave tetrazolopyridopyrimidine 11, the latter compound 11 reduced to 10-amino-derivative 12. Pyridopyrimidine derivatives 4b reacted with hydrazonoylchloride derivatives yielded triazolopyridopyrimidines 14a-c. Also, the reaction of 6b with aromatic aldehydes afforded the arylidines derivatives 16a-d, which were cyclized to triazolopyridopyrimidines deivatives 17a-d. Compound 6b reacted with alpha-haloketones to give triazines derivatives 18 with new ring systems. On the other hand, reaction of 6b with beta-ketoesters afforded 10-pyrazolyl-pyridopyrimidines derivatives 19,20a-c, and 22. The latter compound was coupled with aldehydes and arylamine to give the derivatives 23,24, respectively. The antioxidant activity using ABTS revealed that compound 9 exhibited an inhibitory effect (80%), compound 17c protected the hemolysis of erythrocytes induced by AAPH.