Benzimidazoles 5-nitro

Benzimidazole, l-methyl-2-trichloromethyl-substitution reactions, 5, 432 Benzimidazole, naphthoyl-, 1, 327 Benzimidazole, 5-nitro-alkylation, 5, 390 Benzimidazole, 6-nitro-1-oxide... 

Benzimidazol 5-Nitro-l,2,2,3-tetramethyl-2,3-dihydro- E16d, 266 (Nitrierung)... 

Chichibabin reaction, 5, 409-410 sulfonation, 5, 429 synthesis, 5, 160, 161, 457-498, 496 tautomerism, 5, 365 toxicity, 1, 139 UV spectra, 5, 356, 357 2H-Benzimidazoles 3,3-dioxides synthesis, 6, 407 2V,7ST-dioxides reactions, 5, 456 Benzimidazoles, aryl-oxidation, 5, 433 Benzimidazoles, nitro-mass spectra, 5, 359 reduction, 5, 441 Benzimidazole-2-sulfonic acids reactions... 

Phenylbenzimidazole is nitrated first at the 5-position with mixed acid, and subsequent reaction produces 5-nitro-2-(4-nitrophenyl)-and 5-nitro-2-(3-nitrophenyl)-benzimidazole. 2-Phenyl-, 2-(4-nitro-phenyl)- and 5-nitro-2-phenyl-benzimidazole are nitrated as their conjugate acids. ... 

The localization energies for electrophilic substitution in benzimidazole predict that all three reactive forms should undergo substitution in the 4-position. This does not explain the formation of the 5-nitro compound or that of the 2-deutero compound. It is doubtful whether any electrophilic substitution occurs preferentially in the 4-position. 

Benzimidazole, 2,6-dimethyl-4-nitro-alkylation, 5, 389-390 Benzimidazole, IV-ethyl-sensitizing dyes... 

By using basicity data, Ridd and Smith- showed that 5-nitro- and 5-chloro-benzimidazole and their 2-methyl analogs exist essentially as mixtures of equivalent amounts of 29 and 30, and, in agreement with this ratio, 5-substituted benzimidazoles form comparable amounts of 1- and 3-derivatives on alkylation,- showing earlier alkylation ratios- to be erroneous. There are, however, other factors which can lead to the predominance of one tautomeric form. Basicity measurements indicate that 31 is preferred to the alternative non-hydro-... 

An analogous sequence leads to the anthelmintic agent, etibendazole (50). Reaction of the benzophenone 47, which can be obtained by acylation of o-nitroaniline with g-fluorobenzoyl chloride, with ethylene glycol leads to acetal 48. Sequential reduction of the nitro group and cyclization of the resulting diamine (49) with N,N-dicarbomethoxy-S-methylthiourea gives the benzimidazole etibendazole (50) fl6]. 

Nitro-l-isothiocyanato-benzol wird reduktivzu2-Mercapto-benzimidazol-3-oxid cy-clisiert3 ... 

Auf ahnliche Weise wird 4-Chlor-2-piperidino-l-nitro-benzol zum Benzimidazol-Derivat cyclisiert4 ... 

The fate of the dinitroaniline herbicides in soil is extremely complex and many metabolites have been identified. Golab and Althaus reported 28 metabolites identified in a degradation study of trifluralin in soil. Major degradation products of dinitroaniline herbicides were formed by nitro reduction, A-dealkylation (mono-dealkylated and completely dealkylated) and the ring formation of benzimidazole. 

Azide 367 is prepared from 4-r -butyl-2-nitroaniline in 76% yield by its diazotization followed by treatment with sodium azide. In a 1,3-dipolar cycloaddition with cyanoacetamide, azide 367 is converted to triazole 368 that without separation is directly subjected to Dimroth rearrangement to give derivative 369 in 46% yield. Reduction of the nitro group provides ortfc-phenylenediamine 371 in 91% yield <2000EJM715>. Cyclocondensation of diamine 371 with phosgene furnishes benzimidazol-2-one 370 in 39% yield, whereas its reaction with sodium nitrite in 18% HC1 leads to benzotriazole derivative 372, which is isolated in 66% yield (Scheme 59). Products 370 and 372 exhibit potassium channel activating ability <2001FA841>. 

Preferential reduction of a nitro group in the presence of a carbonyl group in 4-nitroacetophenone ISD, intramolecular rearrangements of o-nitro-benzanilides 32) intramolecular cyclizations of o-nitro-ferf-anilines to benzimidazol-1-oxides 153,154) cyclizations of acylated 2-nitrodiphenylamines to phenazine-l-oxides i ), intramolecular additions of nitro groups to double bonds 156) remarkably ef-... 

Photolytic. Irradiation of trifluralin in hexane by laboratory light produced a,a,a-trifluoro-2,6-dinitro-A-propyl-jo-toluidine and a,a,a-trifluoro-2,6-dinitro-p-toluidine. The sunlight irradiation of trifluralin in water yielded a,a,a-trifluoro-A, 7 -dipropyl-5-nitrotoluene-3,4-diamine, a,a,a-trifluoro-A/ ,A/ -dipropyltoluene-3,4,5-triamine, 2-ethyl-7-nitro-5-(trifluoromethyl)benzimidazole, 2,3-dihydroxy-2-ethyl-7-nitro-l-propyl-5-(trifluoromethyl)benzimidazoline, and 2-ethyl-7-nitro-5-(trifluoromethyl)benzimidazole. 2-Amino-6-nitro-a,a,a-trifluoro-p-toluidine and 2-ethyl-5-nitro-7-(trifluoromethyl)benzimidazole also were reported as major products under acidic and basic conditions, respectively (Crosby and Leitis, 1973). In a later study, Leitis and Crosby (1974) reported that trifluralin in aqueous solutions was very unstable to sunlight, especially in the presence of methanol. The photodecomposition of trifluralin involved oxidative TV-dealkylation, nitro reduction, and reductive cyclization. The principal photodecomposition products of trifluralin were 2-amino-6-nitro-a,a,a-trifluoro-jo-toluidine, 2-ethyl-7-nitro-5-(trifluoromethyl)benzimida-zole 3-oxide, 2,3-dihydroxy-2-ethyl-7-nitro-l-propyl-5-(trifluoromethyl)benzimidazole, and two azoxybenzenes. Under alkaline conditions, the principal photodecomposition product was 2-ethyl-7-nitro-5-(trifluoromethyl)-benzimidazole (Leitis and Crosby, 1974). 

When trifluralin was released in the atmosphere on a sunny day, it was rapidly converted to the photochemical 2,6-dinitro-7V-propyl-a,a,a-trifluoro-/ -toluidine. The estimated half-life is 20 min (Woodrow et ah, 1978). The vapor-phase photolysis of trifluralin was studied in the laboratory using a photoreactor, which simulated sunlight conditions (Soderquist et al., 1975). Vapor-phase photoproducts of trifluralin were identified as 2,6-dinitro-Wpropyl-a,a,a-trifluoro-p-toluidine, 2,6 dinitro-a,a,a-trifluoro-jo toluidine, 2-ethyT7-nitro-l-propyl-5-(trifluoromethyl)benzimidaz-ole, 2 ethyT7-nitro-5-(trifluoromethyl)benzimidazole, and four benzimidazole precursors, reported by Leitis and Crosby (1974). Similar photoproducts were also identified in air above both bare surface treated soil and soil incorporated fields (Soderquist et al., 1975). 

Dihydroxy-2-ethyl-7-nitro-l-propyl-5-(trifluoromethyl)benzimidazole, see Trifluralin... 

Ethyl-7-nitro-4,5-dimethyl-3-hydroxy-2,3-dihydro-benzimidazole, see Pendimethalin 0-Ethyl-0-(p-nitrophenyl)phosphorothioic acid, see Parathion... 

Ethyl-7-nitro-5-(trifluoromethyl)benzimidazole-3-oxide, see Trifluralin 5-Ethyl parathion, see Parathion 0,0-Ethyl-O-phosphorothioate, see Chlorpyrifos, Diazinon. Ronnel... 

A still different scheme is used for the preparation of the benzimidazole buterizine (74). Alkylation of benzhydrylpiperazine with substituted benzyl chloride 70 gives the intermediate 7U Nucleophilic aromatic displacement on this compound by means of ethyl amine leads to reduction of the nitro group then gives the diamine T. Treatment of that with the orthoformate ester of pentanoic acid serves to form the imidazole ring. There is thus obtained the peripheral vasodilating agent buteri zi ne (74). ... 

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