Imidazole 2.4- dinitro

Imidazole, 4,5-dimethyl-lH NMR, 5, 353 <70AHC(12)103, B-76MI40600) Imidazole, 1,2-dimethyl-5-nitro- H NMR, 5, 353 (70AHC(12)103, B-76MI40600) Imidazole, 1,4-dinitro-... 

N-Arylation of azoles is achieved either by using arynes, activated halobenzenes (e.g. dinitro) or under Ullmann conditions. Thus benzyne reacts with imidazoles to give N-arylimidazoles (70AHC(12)103), and these compounds have also been prepared under modified Ullmann conditions. 

Imidazole, 2-methyl-1,4-dinitro-rearrangement, 5, 378 Imidazole, 5-methyl-1,4-dinitro-denitration, 5, 378 Imidazole, l-methyl-4,5-diphenyl-synthesis, 5, 478... 

Unsubstituierte Imidazole reagieren wie zahlreiche andere Nukleophile mit elektronenarmen Halogen-arenen unter nukleophiler Substitution des Halogen-Atoms zu 1 -Aryl-imidazolen. So wird z.B. aus Imidazol mit 4-Fluor-l,3-dinitro-benzol/ Dimethylformamid bei 20° in 91% Ausbeute l-(2,4-Dirtitro-phenyI)-imidazol erhalten769. 

Mit l-Chlor-2,4-dinitro-benzol/Natriumhydrogencarbonat entsteht dasselbc Produkt in nur 35% Ausbeute6/83. Bei verschiedenen 1,2,3,4,5-Pentafluor-benzolen wird selektiv das Fluor-Atom in 3-Stellung substituiert [1 -(2.3,5,6-Tetrafluor-phenyl)-imidazole]771. Das Fluor-Atom in 4-Acyl-l-fluor-benzolen liiBt sich ebenfalls durch Imidazol austauschen [l-(4-Acyl-phenyl)-imid azole]772. 

Aus 4(5)-Nitro-imidazolen erhalt man mit Essigsaureanhydrid/Salpetersaure stabile 1,4-Di-nitro-imidazole601 603, die zu 4,5-Dinitro-imidazolen oder 2,4(5)-Dinitro-imidazo-len umgelagert werden konnen (s. S. 185). Zum eindeutigen Strukturbeweis wurde von 1,4-Di-nitro-imidazol eine Rontgenstrukturanalyse angefertigt603. 

Aus 4,5-Dinitro-imidazol entsteht 4(5)-Chlor-5(4)-nitro-imidazol und aus 4,5-Dinitro-l-me-thyl-imidazol wird regioselektiv 5-ChIor-l-methyl-4-nitro-imidazol erhalten967,968. Vollig analog verlauft auch der Austausch einer Nitro-Gruppe durch ein Brom-Atom mit Bromwasserstoff oder Phosphoroxybromid967,97°. 

Die Substitution einer Nitro-Gruppe in 4,5-Dinitro-imidazol ist auBer durch Halogen-Atome auch durch andere Nukleophile wie Alkanolat, Thiolat oder Amin moglich971. 

Beim Austausch der Nitro-Gruppe in 1-Position von 1,4-Dinitro-imidazol oder 1,4-Dinitro-2-methyl-imidazol mit Methanol oder Ethanol werden als Produkte 4(5)-Methoxy-5(4)-nitro-, 4(5)-Ethoxy-5(4)-nitro-, 4(5)-Methoxy-2-methyl-5(4)-nitro- bzw. 4(5)-Ethoxy-2-methyl-5 (4)-nitro-imidazol erhalten972. 

Bei der Photolyse von l-(2,4-Dinitro-phenyl)-4-phcnyl-imidazol in Ethanol wird der Heterocyclus in einer intramolekularen Redox-Reaktion gespalten. Unter Recyclisierung erhalt man 2-Benzoyl-6-nitro-benzimid-azol [50% Schmp. 255° (Zers.)]326. 

Herbicides that act as inhibitory uncouplers are dinitro-phenols, N-phenylcarbamates, acylanilides, halogenated benzoni-triles, substituted imidazoles, substituted benzimidazoles, bromofenoxim, substituted 2,6-dinitroanilines, pyridinols, and substituted 1,2,4-thiadiazoles (2). 

The reaction of 5-bromo-3-nitro-l,2,4-triazole and 3,5-dinitro-l,2,4-triazole with a variety of oxiranes yielded the expected 1-substituted imidazoles, and also resulted in the formation of 5,6-dihydrooxazolo[3,2-6]-s-triazoles upon treatment with base (75CHE612). The proposed pathway involves proton abstraction from the imidazole and subsequent attack of the oxirane on the N-anion followed by cyclization in a concerted fashion (equation 56). 2,4(5)-Dinitroimidazole reacts analogously with oxiranes to give isomeric nitro-imidazo[2,1 -f>]oxazoles in good overall yield (8UMC601). 

The oxidation of the hydroxymethyl group probably takes place more readily than nitration of the ring [124-127], However, the entry of a nitro group into the imidazole ring without oxidation of the hydroxymethyl group has been reported [107, 110]. Imidazolecarboxylic acids are not nitrated, and their nitro derivatives are therefore obtained by different methods. Nevertheless, the 4- and 5-mononitro-substituted compounds were isolated with the 4,5-dinitro derivative as impurity during the nitration of ethyl l-methylimidazole-2-carboxylate with a mixture of 100% nitric and sulfuric acids at 95°C [128],... 

The nitration of l-methyl-2-(2-furyl)- and l-methyl-2-(2-thienyl)imidazoles in polyphosphoric acid was described [149, 150], At room temperature the nitro group enters at position 5 both of the furan and of the thiophene rings. Nitration of the furan derivative by 2 moles of nitric acid leads mainly to the dinitro derivative l-methyl-2-(5-nitro-2-furyl)-5-nitroimidazole [149], The introduction of a second nitro group into the thienyl derivative requires more rigorous conditions (80°C, 2 moles of nitric acid). Its position in the imidazole ring was not established [150],... 

For many years it was not possible to introduce two nitro groups into the imidazole ring [159], By the use of a somewhat unusual nitration condition (by heating the substrate first with nitric add and then with the sulfuric-nitric acid mixture) it was possible to obtain 4,5-dinitroimidazole [79], The method has now also been used for the production of 4,5-dinitroimidazoles [84, 93, 160], It was also shown that C-polynitrobisimidazoles [79] and not /V-nitroimidazolcs, as considered earlier [161], are formed during the nitration of 2,2 -bisimidazole and its bromine derivatives. As already mentioned earlier, during the nitration of ethyl l-methylimidazole-2-carboxylate the 4,5-dinitro derivative was also isolated together with the other nitration products [128], Increase in the reaction time increases the amount of the dinitro derivative. 

The nitration of 1,4,5-trimethylimidazole 3-oxide with the sulfuric-nitric acid mixture leads to the 2-nitro derivative [76, 162], Both this compound and 1-meth-ylpyrazole 2-oxide enter into reaction in the form of the free base [76], The nitration of 2-aryl-1-hydroxyimidazole 3-oxides leads either to cleavage of the imidazole ring or to the formation of the 4-nitro or 4,5-dinitro derivatives, depending on the reaction conditions [162] (Scheme 15). 

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. 

Imidazol 2-Cyclopropyl-4,5-dicarbo-xy- E8c, 13 [2,3-(OH)2 —butandi-saure/HN03 R-CHO/NH3] Methan Dinitro-(4-methyl-phenyl)-IV/la, 765... 

Imidazol 2-Cyclobutyl-4,5-dicar-boxy- E8c, 13 [HOOC-CH(OH) - CH(OH) - COOH/ HN03 + R-CHO(NH3)] Methan (2,4-Dimethyl-phenyl)-dinitro- IV/la. 765 Methannitronsaure (4-Nitro-phenyl)- -ethylester X/l, 158, 446... 

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