Synthesis of pyrazolone derivatives. XXXX. Synthesis and analgesic activity of 4-alkoxyimino (or alkylaminomethylene)-3-methyl-carbamoyl-1-methyl(or phenyl)-2-pyrazolin-5-ones (author's transl)

Abstract

Syntheses of 4-alkoxyimino (or alkylaminomethylene)-3-methylcarbamoyl-1-methyl (or phenyl)-2-pyrazolin-5-ones were carried out to test their analgesic activity. The reaction of 3-ethoxycarbonyl-1-methyl (or phenyl)-5-hydroxypyrazole (Ia, b) with sodium nitrite in hydrochloric acid or acetic acid gave 3-ethoxycarbonyl-4-hydroxyimino-1-methyl (or phenyl)-2-pyrazolin-5-one (IIIa, b), which were converted to amides (Va, b). The reaction of Ib with N, N'-diphenylformamidine in acetic anhydride gave 4-anilinomethylene-3-ethoxycarbonyl-1-phenyl-2-pyrazolin-5-one (VII), whose reaction with 30% methylamine methanol solution gave 4-anilinomethylene-3-methylcarbamoyl-1-phenyl-2-pyrazolin-5-one (VIII) (9.4%) and 4-(N-methylaminomethylene)-3-methylcarbamoyl-1-phenyl-2-pyrazolin-5-one (IX) (64.9%). VIII showed analgesic activity in mice.