3-Iodo- 1-methylpyrazole-4-carboxylic acid

The reaction of the isomeric 3-iodo-l-methylpyrazole-4-carboxylic acid with copper phenyl- and p-amylacetylide also leads to closure of the pyranopyrazole... 

The cyclocondensation of 4-iodo-l-methylpyrazole-5-carboxylic acid with PhC=CCu under similar conditions is over in 1.5 h. Thus, the cyclization of the... 

Such an easy isomerization of acetylenylbenzoic acid amides implies the formation of a five-membered nonaromatic ring condensed with the pyrazole ring. However, the pyrazole analog of o-iodobenzamide (amide of 4-iodo-l-methylpyrazole-3-carboxylic acid) formed under heating with CuC=CPh in pyridine for 9 h only the disubstituted acetylene in 71 % yield is identical in all respects to the compound obtained from the corresponding acid by successive action of SOCI2 and NH3 (90IZV2089) (Scheme 126). 

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. 

The cyclocondensation of 4-iodo-l-methylpyrazole-5-carboxylic acid with PhC CCu under similar conditions is over in 1.5 h. Thus, the cyclization of the 4-phenylethynyl-l-methylpyrazole-5-carboxylic acids and the cyclocondensation of the iodine acid with PhC CCu give the same products pyranopyrazoles. However, the formation rate of the first reaction is much higher. 

In the heterocyclization reactions of 4-acetylenyl-l-methylpyrazole-3-carbox-ylic acids and 4-acetylenyl-l-methylpyrazole-5-carboxylic acids the behavior is the same. Isomeric I-methyI-4-phenyIethynyIpyrazole-3-carboxylic acid forms 3 -lactones, 2-methyl-7-oxo-5-phenylpyrano[3,4-c]pyrazole, in 71 % yield (20 min) (Scheme 122). The same ester is obtained by acetylenic condensation (3 h) of 4-iodo-l-methylpyrazole-3-carboxylic acid with copper phenylacetylide. 

---