Synthesis of pyrazolone derivatives. XXXIX. Synthesis and analgesic activity of pyrano(2,3-c)pyrazoles.

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Abstract
Synthesis of pyrano[2,3-c]pyrazoles by reaction of 3-ethoxycarbonyl-5-hydroxy-1-methyl(or phenyl)pyrazole (1a, b) and acetylenecarboxylates or ethyl acetoacetate were examined. The reactions of 1a,b with acetylenecarboxylates gave 3-ethoxycarbonyl-4-substituted-1-methyl(or phenyl)pyrano[2,3-c]pyrazol-6(1H)-ones in 5.9-23.9% yields. The Pechmann-Duisberg reaction of 1a-c with ethyl acetoacetate gave 3-ethoxycarbonyl-4-methyl-1-substituted pyrano[2,3-c]pyrazol-6(1H)-ones in 33.1-46.2% yields. Similar reactions of 5-hydroxy-3-methylcarbamoyl-1-phenyl(or m-chlorophenyl)pyrazoles with ethyl acetoacetate gave 4-methyl-3-methyl-carbamoyl-1-phenyl(or m-chlorophenyl)pyrano[2,3-c]pyrazol-6(1H)-ones in 17.4-30% yields. The newly synthesized pyrano[2,3-c]pyrazoles showed analgesic activity in mice when tested by 2 methods.