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-1-substitutedpyrano [2, 3-c] pyrazol-6 (1H)-ones (VIIa-c) in 33.1-46.2% yields. Similar reactions of 5-hydroxy-3-methylcarbamoyl-1-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.