Benzimidazole 3-oxides decarboxylative

Synthesis of compound 68 by oxidative decarboxylation of adamantane carboxylic acid is described in [25], Initially, for the synthesis of 2-(l-adamantyl)benzimidazole (68), adamantan radical was obtained in sulphuric acid diluted by silver nitrate in the presence of ammonia persulfate. Then, the synthesized radical was inserted directly into the heterocycle. After N-methylation, 2-(l-adamantyl)benzimidazole (68) was transferred in l-methyl-2-(l-adamantyl)-benzimidazole (79). The experiments carried out on chicken embryo revealed high antiviral activity of both obtained compounds [25] ... 

H- Benzimidazole, 2,2-pentamethylene-reduction, 5, 423 Benzimidazole-2-carbaldehyde oximes, 5, 436 Benzimidazolecarbaldehydes oxidation, 5, 437 Benzimidazole-2-carbamates 5-substituted as anthelmintics, I, 202 Benzimidazole-l-carboxylic acid, 2-amino-methyl ester reactions, 5, 453 Benzimidazole-2-carboxylic acid decarboxylation, 5, 435 Benzimidazole-3-carboxylic acid, 1-hydroxy-ethyl ester synthesis, 6, 407 Benzimidazoles acidity, 5, 50, 385, 386 acylation, 5, 71, 391, 402, 417 N-alkyl-... 

The reaction of iV-(2,4-dinitrophenyl)amino acids with base in aqueous dioxane has been shown to give benzimidazole iV-oxides (7). The rate-determining step is likely to be formation of an iV-alkylidene-2-nitrosoaniline intermediate (6), which is followed by rapid cyclization and decarboxylation.19 The loss of carbon dioxide from perbenzoate anions has been investigated by mass spectrometry and electronic structure calculations. The results, including isotopic labelling experiments, support a mechanism involving initial intramolecular nucleophilic attack at either the ortho- or ipso-ring positions. They also indicate that epoxides may be intermediates en route to the phenoxide products.20 There has also been a theoretical study of the formation of trichlorinated dibenzo-/ -dioxins by reaction of 2,4,5-trichlorophenolate ions with 2,4-dichlorophenol.21... 

Poly(benzimidazoles) are produced from dicarboxylic acids and aromatic tetramines. Commercially, 3,3 -diaminobenzidine tetrahydrochloride and diphenyl isophthalate are preferentially used. The diphenyl ester is used because (a) the free acids decarboxylate under the high reaction temperatures of 250-400 C (b) the acyl chlorides react too fast, making ring closure difficult and (c) the amino groups are partially methylated if the methyl esters are used. The hydrochloride is used because it is more stable to oxidation than the free amine itself. The polycondensation is carried out in two stages. A prepolymer. A, is formed in the first stage with foaming and phenol elimination ... 

Acetic acid/irradiation Benzimidazole 3>oxides by decarboxylative ring closure... 

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