Verfahren zur Herstellung von 2-substituierten Benzimidazolen

摘要

Novel benzimidazoles of the formula wherein R1 represents a hydrogen atom or a C1- 5 alkyl, aralkyl or acyl radical, one of R5 and R6 represent a hydrogen or halogen atom or a C1- 5 alkyl, C1- 5 alkoxy, C1- 5 alkylthio, phenoxy, phenylthio, phenyl or halophenyl radical and the other represents hydrogen and n is 1 or 2, are prepared by reacting a substituted aniline and a substituted furan of the respective formulae wherein A represents hydrogen or a nitro group and B represents a carboxy, esterified carboxy or haloformyl radical, to form an amide of the formula when A is hydrogen, nitrating this amide to convert A to nitro, and reducing the nitro compound with hydrogen (under certain conditions and when n is 2, the reduction may cause the elimination of one chlorine atom); by reacting the required o-phenylene diamine with the required chloro-substituted-2-furfural, the process being effected in the presence of nitrobenzene benzene or being followed by reaction with an oxidizing agent on the intermediate Schiff type base formed; or by reacting an amidine of the formula wherein R5, R6 and n have the above significance (obtainable from the required aniline and required chloro substituted 2-cyano-furan), with a chlorinating or brominating agent to produce the corresponding N-haloamidine and treating this compound with a base. Ethyl - 2,3,4,5 - tetrachloro - tetrahydrofuran - 2 - carboxylate is prepared by treating ethyl 2-furoate with chlorine, is converted into a mixture of ethyl mono- and poly-chloro-2-furoates by heating the mixture may be separated by fractionally distilling, saponifying the fraction boiling between 123 DEG and 145 DEG C. at 20 mm. pressure, forming the calcium salts of the resulting mixture of acids, filtering off the precipitated calcium salts and acidifying the filtrate to precipitate 3,5-dichloro-2-furoic acid or treating an aqueous solution of the said calcium salts with hydrochloric acid and extracting 4,5-dichloro-2-furoic acid. 4 - Chloro - 2 - furoic acid is prepared by the zinc dust-HCl treatment of the corresponding 4,5-dichloro-compound. 4 - Fluoro - 41 - aminobiphenyl is prepared by nitrating 4-fluoro-biphenyl and reducing the resulting 4-fluoro-41-nitrobiphenyl. Pharmaceutical compositions having anthelmintic activity contain as the active ingredient a compound of the first formula above. The compositions may be in the form of capsules, tablets, boluses, drenches or solutions.