1- Bromo-4-nitropyrazole

Bromo-4-nitropyrazole 19 is obtained by bromination of 4-nitropyra-zole with sodium hypobromite in water-acetic acid [55LA(593)179]. 3,5-Dimethyl-4-tropylpyrazole is brominated with /V-bromosuccinimide to form a mixture of Af-bromoderivative 20,4-bromo-3,5-diethylpyrazole, and 7-tropylsuccinimide (64BCJ1018) (Scheme 7). 

Bromo-5-nItrofuran, AC25 Bromonitromethane, AAlO 2-Bromo-5-nitrooxole, AC25 2-Bromo-2-nitropropane, AB74 4-Bromo-l-nitropyrazole, AB20... 

The halogen atom acts as a functional group more often than others during substitutive nitration. During the nitration of 4-bromo-3-methylpyrazole with a mixture of nitric acid and oleum 3-methyl-4-nitropyrazole is formed [62] (Scheme 46). 4,5-Dibromo-3-methylpyrazole is nitrated similarly [367, 368],... 

Parallel i/wo-ni (ration at position 4 and nitration at position 5 of the pyrazole ring were also observed during the action of the sulfuric-nitric acid mixture on 1,3-dim-ethyl-4-bromopyrazole [369], The released bromine cation partly brominates the initial reagent with the formation of l,3-dimethyl-4,5-dibromopyrazole. The latter is subsequently transformed into l,3-dimethyl-5-bromo-4-nitropyrazole (see the Scheme later). The nitration of l,3-dimethyl-4,5-dibromopyrazole leads to the formation of l,3-dimethyl-5-bromo-4-nitropyrazole and l,3-dimethyl-4-nitropyrazole [369] (Scheme 48). 

The reaction of sodium azide with l-bromo-l-nitro-2-arylethenes takes place by a formal 1,3-cycloaddition Scheme leading to 4(5)-aryl-5(4)-nitro-l,2,3-triazoles [487-489], During the synthesis of nitrotriazoles the bromonitroarylethenes can be replaced successfully by the more readily obtainable l,2-dibromo-l-nitro-2-arylethanes [489], The intermediate product in the synthesis of 3-nitropyrazoles from 2,2-dinitroethanol and diazo ketones or diazoacetic ester is 1,1-dinitroethene [490,491] (Scheme 68). 

The preparation of 5-acetamido-3-bromo-l-(2,6-dichloro-4-trifluoromethylphenyl)-4-nitropyrazole and derivatives is described (4). 

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