Synthesis of Pyrazoles Condensed to Five-Membered Rings

Three systems (166, 167, and 168) are aromatic lOTrelectron systems. Mesoionic derivatives of 169 are aromatic as are salts of 170. 

In the following sections we describe synthetic routes to ring systems whether or not the products are aromatic lOTrelectron systems. 

5-Chloro-4-(2-chlorobenzoyl)-1 -phenyl-3-methylpyrazole yields 1 -phenyl-4-(2-chlorophenyl)-3-methylpyrazole upon treatment with hydrazine (17CB737). Other derivatives of pyrazolo [3,4-c] pyrazoles have been similarly prepared (22CB291). 

5-diphenyl-6-imino-2,3,4,5-tetrahydropyrazolo[4,3-c]pyrazol-3-one form ethyl 3-cyano-2,3-diphenylhydrazonobutanoate has been reported (34LA97). Arylazoethynlarenes give pyrazolo[4,3-c]pyrazoles upon heating in solution (69CC1393). 

6-dioxo-l,4-diazabicyclooct-2,5-enes (80GEP2855193). Also, the reaction of carbon suboxide with pyrazoles gives pyrazolo[l,2-a]pyrazoles (86CC144). 

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III. Synthesis of Pyrazoles Condensed to Five-Membered Rings. 251... 

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