Benzimidazole 3-oxide benzimidazolines

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). 

The reaction of 1,2-diaminonitrobenzenes with aldehydes is a widely accepted synthetic route to nitrobenzimidazoles [57, 62,63,66, 350,372-383], This reaction passes sequentially through a stage of the formation of azomethines (Schiff s base) and benzimidazolines. On oxidation the latter forms the corresponding benzimidazole derivatives (Scheme 2.44). 

The reaction between o-phenylenediamine and an equimolar amount of an aromatic or heterocyclic aldehyde has been shown to proceed by initial formation of a monoanil (74). In the presence of oxidizing agents (e.g. nitrobenzene, which also acts as the solvent) this can form the 2-substituted benzimidazole. With two moles of aldehyde the bis-anil (75) forms, giving rise to a 1,2-disubstituted benzimidazole (Scheme 42). This aldehyde route to benzimidazoles is particularly suited to the synthesis of compounds with a heterocyclic group (e.g. 2-thienyl-, 2-pyridyl-) at C-2. Reaction of 2,2,4,4-tetrakis(trifluoromethyl)-l,3-dithietane with o-phenylenediamine gives 2,2-bis(trifluoromethyl)benzimidazoline (7430785). 

Dinitro-r-anilines constitute a major group of pre-emergent herbicides. The photodecomposition of these herbicides has been simulated by studying the photolysis of one typical example, Trifluralin 47 (74MI1). The major product from the action of sunlight in aqueous alkaline media was the benzimidazole 48, and the by-products included the dihyroxybenzimidazo-line 49, the benzimidazole Y-oxide, and benzimidazoline derivatives of 48, all being derived by r-amino-effect chemistry (Scheme 17). 

Benzimidazoles and an Imidazoquinoline. - Aryl sulphimides p-RC6H4NSMe2 (R = Cl, Br, or NO2) react with nitrile oxides ArCNO to yield mixtures of benzimidazole A -oxides (300) and 1,2,4-benzoxadiazines (301). The betaine (302) results from the action of Chloramine T on benzimidazoline-2-thione. A -Phenylcarbimide dichloride, PhN=CCl2, reacts with the amidine... 

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