Pyrazole 3.5- dinitro

Pyrazoles can undergo nitration at several positions 4-bromo-l-methylpyrazole yields the 3,5-dinitro product. 1-Methylpyrazole 2-oxide yields the 5-nitro derivative. 

It has already been mentioned that 5-methylisoxazole is converted into a pyrazole derivative by phenylhydrazine. All 4-nitroisoxazoles undergo this same reaction (136— 137)/° 5,5 -Dimethyl-4,4 -dinitro-3,3 -diisoxazolyI reacts similarly... 

Thermolysis reactions have also been investigated as methods for preparing pyrazoles. Thermolysis of azido imines 18 led to 2-substituted-4,6-dinitro-2//-indazoles 19 <00S1474>. High temperature intramolecular cyclization of AA-diethyl-A -(4-substituted-2-... 

Ndls. Was prepd by treating an alkaline soln of 3,4-dinitro-5-pyridyl -pyrazole with HaS at 90°... 

The nitration (fuming nitric acid) of 5-chloro-3-methyl-l-phenylpyrazole is reported to give a mononitro product (presumably the 4-nitrophenyl derivative) and a dinitro product 5-chloro-3-methyI-4-nitro-l-(4-nitro-phenyl)-pyrazole (1900CB2595 11LA329). 

The nitration of 3-methoxy-5-methyl-l-phenylpyrazole with nitric acids sulfuric acid at 0°C, followed by 3 h at 50°C, gives 3-methoxy-5-methyl-(4-nitrophenyl) pyrazole (51%), but reaction with mixed acid at 40°C for 24 h gives the 4-nitro-l-(4-nitrophenyl) product (85%). The preparative nitrations (using mixed acid) of the dinitro products are summarized in Table III. No n.m.r. evidence was found for the presence of ortho or meta nitrophenyl isomers. 

HMordenite, HFaujasite-780, HFaujasite 720 and Na-Faujasite zeolites. Among the different catalysts, HFaujasite-720 was the most active and selective catalyst towards 2,4-dinitrotoluene, achieving a yield of dinitrotoluenes of 92 % with a ratio of 2,4- to 2,6- isomers of 4.3 1 in 3 min reaction time. Using this zeolite, l-chloro-2-nitrobenzene and pyrazole were also nitrated regioselectively to obtain l-chloro-2,4-dinitrobenzene in a l-chloro-2,4-dinitro l-chloro-2,6-dinitro ratio of 30 1, and 1,4-dinitropyrazole in 80% yield, respectively. The authors proposed a nitration mechanism in which the protons in the zeolite are replaced by nitronium ions derived from N2Os in a fast pre-equilibrium process. This produces active sites for transfer of nitronium ion from faujasite to aromatic in the rate-controlling step. 

The introduction of other electron-withdrawing or -donating groups enables nitration of one or another of the rings to be accomplished selectively. Thus, l-phenyl-3-methylpyrazole is nitrated only in the pyrazole ring, whereas 1 -phenylpyrazole-3-carboxylic acid nitrates only in the para position of the benzene ring.586 The only dinitro-pyrazole recorded was obtained from 3-nitro-5-(pyrid-3-yl)-pyrazole.249,587 In the nitration product (54) the nitro group at... 

In some cases l-methyl-5-nitro- and l-methyl-3,5-dinitropyrazole can form as a result of deoxygenation [76], Nevetheless, the nitration of 2-benzylpyrazole 1-oxide by sulfuric-nitric acid mixture leads to 2-benzyl-3-nitropyrazole 1-oxide in quantitative yield. Further nitration takes place in the phenyl 4-position forming 3-nitro-2-(4-nitrobenzyl)pyrazole 1-oxide and then in the pyrazole 5-position to give 3,5-dinitro-2-(4-nitrobenzyl)pyrazole 1-oxide as the final product [77],... 

In certain cases l,2-dinitro-2-phenylethene also forms the corresponding nitro-pyrazoles in reaction with diazoalkanes [492 194] (Scheme 69). 

The kinetics of hydrolysis of energetic material precursors - mono- and dinitro derivatives of pyrazole, imidazole, 1,2,4-triazole, and isoxazole has been studied by the polarographic and photometric methods [647], The alkaline hydrolysis rate constants experimentally determined depend on the nature of the heterocycle. A possible mechanism for hydrolytic transformations of nitroazoles is proposed on the basis of the calculated thermodynamic parameters of the reaction. 

The chemical properties of 1,4-dinitropyrazole [654] and l,4-dimethyl-3,5-dini-tropyrazole obtained by the nitration of 1,4-dimethylpyrazole [655], nitrotriazoles [656-663], and other nitroazoles [662, 664-666] have been studied. 1,4-Dinitro-pyrazole undergoes ring transformation reactions with primary amines, hydrazines, hydroxylamine, and amidines [654], Acid hydrolysis of dinitropyrazole leads to (l-methyl-3,5-dinitropyrazol-4-yl)acetaldehyde, and the reaction with sodium nitrite in hydrochloric acid furnishes 2-hydroxymino-2-(l-methyl-3,5-dinitropyra-zol-4-yl)acetaldehyde [655],... 

Mass spectrometry has been used for the structural determination of isomeric I -methyl-3(5)-nitro-4-pyrazolcarbonitriles [302], l,5-dimethyl-3,4-dinitropyrazole [279], 4,4-dinitro-l,l-methylenedipyrazole [1291], 3-amino-5-bcnzylamino-4-nitro-yrazole [317], amino derivatives of 4-nitropyrazole [1292], antibacterial compounds 3-(3-mcthyl-4-nitro- lf/-pyrazole-5-yl)- and 3-(3-methyl-4-nitro-l-alkylpyrazole-5-yl)-5-methyl-4-nitroisoxazoles [500], some l-heteroaryl-4-nitropyrazoles [311]. 

Reaction of l-methyl-4-nitropyrazole with 1,1,1-trimethylhydrazinium halides in the presence of sodium methoxide or potassium fert-butoxide afforded 5-amino-l-methyl-4-nitropyrazoles <1999CHE1109>. Specifically, the primary radical anions of substrate in the vicarious nucleophilic substitution of hydrogen in 1-methyl-4-nitropyrazole 192 with 1,1,1-trimethylhydrazinium iodide yielded 5-amino-l-methyl-4-nitropyrazole 193, which was studied by electron spin resonance (ESR) (Equation 31) <2005MRC1023>. Reaction of 3,5-dinitropyrazole 194 with trimethylhydrazinium iodide in DMSO afforded 4-amino-3,5-dinitro-l//-pyrazole 195 via another vicarious nucleophilic substitution (Equation 32) <2001JHC1227>. 

Nitropyrazole derivatives such as 4-nitropyrazole, l-methyl-4-nitropyrazole and 4,4 -dinitro-l,r-methylene dipyrazole are known as antiparasitic agents <88Mi 30i-02>. It has been shown that 3,4-bis(2,4-dinitrobenzoyl-hydroxymethyl) pyrazole has remarkable antimicrobial activity it is more efficient than penicillin, levomycetin, and polymyxin <92Ml 30i-03>. The synthesis of A -pyrazoline-... 

In IH-Pyrazol (Dichlormethan) betragen die chemischen Verschiebungen fur C-3 und C-5 134,6 ppm, fur C-4 105,8 ppm. Mit wachsender Elektronegativitat der Substitucntcn in 1-Position verschieben sich alle Signale nach tieferem Feld (z.B. Benzyl < Benzoyl < Benzolsulfonyl % 4-Methyl-benzolsulfonyl < 4-Nitro-benzolsulfonyl < 2,4-Dinitro-benzolsulfonyl)1738. 

Geht man direkt von 1,3-Dinitro-alkanen aus, werden mit Hydrazin-Hydrat und 1,3-Dinitro-2-phenyl-butan oder 2,4-Dinitro-3-(4-methoxy-phenyl)-pentan 3(5)-Methyl-4-phenyl- (56% Schmp. 140-142°) bzw. 3,5-Dimelhyl-4-(4-methoxy-phenyl)-IH-pyrazol (68% Schmp. 153-155°) erhalten. 1-Nitro-l-alkene cyclisieren thermisch in Dimethylformamid mit D-Ga-lactose-phenylhydrazon2138 ... 

Arylhydrazone von 3-(l-Adamantyl)-3-chlor-acrolein und 3-(l-Adamantyl)-3-chlor-2-methyl-acrolein geben beim Erhitzen in einem Phosphorsaure/Essigsaure-Gemisch661 oder in Phos-phorsaure6625-( l-Adamantyl)-l-( 2,4-dinitro-phenyl)-(41 % Schmp. 163,5 165,5°), 5-( 1-Ada-mantyl)-l-(2,4-dinitro-phenyl)-4-methyl- (54% Schmp. 199,5-200,5°)661 bzw. 5-( 1-Adaman-tyl)-1-phenyl-lH-pyrazol (48% Schmp. 135-136°)662 ... 

Beim Erhitzen von 1 Equivalent a-Diazo-carbonyl-Yerbindung und 1,1 Aquivalenten 2,2-Di-nitro-ethanol in Benzol auf 50-60° werden 3(5)-Acyl-5(3)-nitro-l H-pyrazole gebildet. 2,2-Dinitro-ethanol eliminiert Wasser das in situ gebildete 1,1-Dinitro-ethen geht dann die Cycloaddition ein872. 

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