2- -5-methylpyrazol-3,4-dione

The proton spectra of 1-substituted 3-nitropyrazoles [296], 5-substituted 3-methyl-l-aryl-4-nitropyrazoles [297, 298], 1,3- and l,5-diphenyl-4-nitropyra-zoles [281], 5-iodo-4-nitro-l,3-dimethylpyrazole [299], l-methyl-3-nitro-4- and l,3-methyl-4-nitro-5-phenylethynylpyrazoles [300], l-methyl-3-nitro-5-methoxy-carbonylpyrazole [301], l-methyl-3-nitro- and l-methyl-5-nitro-4-cyanopyrazoles [302], A-(2,4-dinitrophenyl)nitropyrazoles [303], a- and [3-anomers of 3-nitro-and4-nitropyrazolyl-l-ribonucleosides [304, 305], 3-substituted 1,5-dimethyl- [306] and 5-substituted l,3-dimethyl-4-nitropyrazoles [279], l-acetyl-3-anilino-4-nitro-5-dimethylaminopyrazoles [307], 3-substituted 4-nitro-5-carboxylic acid derivatives [308, 309], 4-nitropyrazolo[4,3-e][l, 4]diazepin-5,8-diones showing antimicrobial activity [310], l-heteryl-4-nitropyrazole derivatives [311], 3-nitro- and 5-nitro-l-methylpyrazole [312], 4-nitro-5-(trimethylsilyl)pyrazole [313], 3-methyl-4-nitro-pyrazol-5-ones [298], and some other nitropyrazoles [248, 314-320] have been examined. 

Cyclocondensation of 3-amino-5-methylpyrazole with 2-arylmethyli-dene-5,5-dimethylcyclohexane-l,3-diones or 9-aryl-3,3,6,6-tetramethyl-2,3,4,5,6,7,8,9-octahydro-lH-xanthene-l,8-diones, in DMF or methanol gave 4-aryl-3,7,7-trimethyl-l,4,6,7,8,9-hexahydropyrazolo[3,4- 7]quinolin-5-ones 323 whose structure was proved by the X-ray diffraction data (06RJOC1015). 

In a catalyst-free, aqueous-mediated MCR facilitated by sonication, isat-ins 200, 5-amino-3-methylpyrazole 201 and a-mercaptoacetic acids 202 reacted to form spiro(indole-3,4 -pyrazolo[3,4-e][l,4]thiazepines) 203 in high yield. Replacement of the isatin with acenaphthylene-1,2-dione or N-substitued piperidin-4-ones gave the corresponding spiro(pyrazolo-1,4-thiazepines) (13RA18992). 

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