1 13 hydropyridazinones I1 in which R'and R2 are hydrogen and R3NH is a para substituent. Cyclization of 40 and 41 with hydrazine hydrate gave the amino-and (acetyl- amino) dihydropyridazinones 1 and 3, respectively. Heating 1 in formic acid gave the formylamino compound 2.8 Treating the amino acid 41 with formic acid led to the y-keto acid 42, which with hydrazine hydrate again gave 2. The (alkanoy1amino) phenyl derivatives 4 ...