Abstract Whereas treatment of the ethyl 5-acetyl-2-amino-4-methyl-thiophene-3-carboxylate (1) with potassium hydroxide yields the 2-hydroxy-thiophene-3-carbonitrile 4 its hydrazone 2 is converted into the 1-amino-5-mercapto-2-pyridone derivative 6. The transformation of the 2-amino-5-phenylazo-thiophene derivative 9 by potassium hydroxide yields the substituted 3-mercapto-pyridazin-6 (1 H) one 10, with sodium ethoxide the 5-phenylhydrazono-2-oxo- ...
