Benzimidazoles reaction with chloroform

Preparation of 2-(4-methyl-l-piperazinyl)benzimidazole. A mixture of 2-chlorobenzimidazole (10.00 g) and N-mehylpiperazine (20.00 g) is stirred at 125°C for 5 hours. A 10% aqueous sodium hydroxide (100 ml) is added to the reaction mixture, and the precipitated crystals are separated by filtration. The filtrate is extracted with chloroform, and the chloroform extract is evaporated to dryness to give the same crystals. The crystals are combined and recrystallized from water-methanol to give 2-(4-methyl-l-piperazinyl)benzimidazole (7.02 g) as colorless needles, m.p. 225°-226°C. 

The dibromo derivatives 125a and 126a have been prepared by reaction of the unsubstituted amine 125c and the methanesulphonate salt of 126c with excess bromine in acetic acid. Amines 125b and 126b have been converted to the isothiocyanates 125 and 126 by reaction with thiophosgene in a biphasic chloroform-bicarbonate system. The radiochemical purity and the specific radioactivity of the isothiocyanate 125 were 99.9% and 27.4 Ci mmol -1, respectively. The benzimidazole isothiocyanate 126 has been prepared with >95% radiochemical purity and with specific activity of 16.3 Ci mmol -1. 

The reaction of chloroform with imidazoles > benzimidazoles and secondary amines (especially alicyclic amines) in the presence of alkoxides or hydroxides, as well as the reaction of chlorodifluoro-methane with sodium N-alkyl-iV-arylamides furnishes trisaminomethanes (525) and (526) (Scheme 95), respectively. Aziridine transforms fluorodialkyl sulfide (527) to the orthoamide (528 equation... 

It is prepared by the reaction of sodium or potassium thiocyanate with chloroformic acid methyl ester, and the intermediate product reacts with o-phenylene diamine to form the thiophanate. Thiophanate-methyl is a colourless, crystalline compound hardly soluble in water. It forms unstable salts and complexes with bivalent ions in alkaline solutions. The range of action of each thioallophanic acid derivative is identical with that of the benzimidazole derivative into which it is converted in the plant. Thiophanate-methyl has both a preventive and a curative action. 

In 1974-75, works concerning the synthesis of pharmacologically active 1-adamantylsubstituted compounds were published [59, 60], In order to obtain preparations of antiviral activity, benzimidazole derivatives with substituted in the second position adamantyl and adamantoylaminoalkyl groups. First, iminoester was obtained using Pinner reaction and then condensation of the iminoesters with o-phenylenediamines in chloroform environment was provided using King method [61],... 

A mixture of l-[(2 -cyanobiphenyl-4-yl)methyl]-2-ethoxybenzimidazole-7-carboxylate (0.7 g) and trimethyltin azide (0.7 g) in toluene (15 ml) was heated under reflux for 4 days. The reaction mixture was concentrated, and to the residue were added methanol (20 ml) and 1 N HCI (10 ml). The solution was stirred at room temperature for 30 minutes and adjusted to pH 3-4 with 1 N NaOH. After removal of the solvent, the residue was partitioned between chloroform and water. The organic layer was evaporated to dryness to dive a syrup. The syrup was purified by column chromatography on silica gel to give crystals. Recrystallization from ethyl acetate-benzene afforded colorless crystals ethyl 2-ethoxy-l-[[2 -(lH-tetrazol-5-yl)biphenyl-4-yl]-methyl]benzimidazole-7-carboxylate (0.35 g, 45%), M.P. 158-159°C. 

As the reaction of 2-bromocyclobutanone with 1,2-phenylenediamine was carried out in 80% acidic aqueous methanol, ring contraction of a 2-bromocyclobutanone hydrate, hemiacetal or dimethyl acetal to cyclopropanecarboxylic acid (Section 4.1.2.2.4), followed by a Philipps-type benzimidazole synthesis could explain the formation of the 2-cyclopropylbenzimidazole (8). However, the reaction proceeded equally well in an aprotic solvent such as chloroform. Therefore, direct ring contraction of a 2-bromo-l,l-(l,2-phenylenediamino)-... 

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