Keten dithioacetals. Part 11. Reaction of 3-cyano-4-methylthio-2(1H)-pyridones with hydrazine and guanidine: synthesis of novel substituted and fused pyrazolo[4,3-c]pyridone and pyrido[4,3-d]pyrimidine derivatives

The N-methylpyridones (2a–f) were prepared by alkylation of the pyridones (1a–f) with dimethyl sulphate, followed by heating the mixture of N-methyl (2) and O-methyl (3) products with methyl iodide. The pyridone (4c), the quinolone (4d) and the benzoquinolone (5b) derivatives were prepared in the same manner. Treatment of the pyridones (2a–f) and (1a–i) with hydrazine in refluxing propan-2-ol yielded the respective pyrazolo-[4,3-c]pyridone derivatives (7a–o) in excellent yields, and the fused pyridones (4a–e) and (5a–d) afforded the respective fused pyrazolopyridone derivatives (8a–e) and (9a–d) in excellent yields under identical conditions. The reactions of the N-methylpyridones (2a–f), (4c–d), and (5b) with guanidine in the presence of 2 mol of sodium ethoxide similarly gave substituted and fused pyrido [4,3-d]pyrimidine derivatives (11a–f), (12a–b), and (13), respectively.