Synthesis of Pyrazolone Derivatives. XXXIX. Synthesis and Analgesic Activity of Pyrano[2,3-c]pyrazoles

Abstract

Syntheses of pyrano[2,3-c]pyrazoles by means of the reaction of 3-ethoxycarbonyl-5-hydroxy-1-methyl(or phenyl)pyrazole (Ia, b) and acetylenecarboxylates or ethyl acetoacetate were examined. The reactions of Ia, b with acetylenecarboxylates gave 3-ethoxycarbonyl-4-substituted-1-methyl(or phenyl)pyrano[2,3-c]pyrazol-6(1H)-ones (IIa–c) in 5.9–23.9% yields. The Pechmann-Duisberg reaction of Ia–c with ethyl acetoacetate gave 3-ethoxycarbonyl-4-methyl-l-substitutedpyrano[2,3-e]pyrazol-6(1H)-ones (VIIa–c) in 33.1–46.2% yields. Similar reactions of 5-hydroxy-3-methylcarbamoyl-l-phenyl(or m-chlorophenyl)pyrazoles (IXa, b) with ethyl acetoacetate gave 4-methyl-3-methylcarbamoyl-1-phenyl(or m-chlorophenyl)pyrano[2,3-c]pyrazol-6(1H)-ones (Xa, b) in 17.4–30% yields. The newly synthesized pyrano[2,3-c]pyrazoles (Xa, Xb, XII) showed analgesic activity in mice when tested by two methods. © 1981, The Pharmaceutical Society of Japan. All rights reserved.