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

Abstract

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.