| 摘要 |
<p>The invention comprises compounds of the formula <FORM:1009807/C2/1> where R is a five-membered heterocyclic ring attached by a carbon atom to the rest of the molecule and containing N and S, X is Cl or Br, and R1 and R2 are hydrogen, C1-5 alkyl or C1-5 alkoxy, at least one being hydrogen; their production by treating the corresponding amidine or a hydrohalic acid addition salt thereof with a halogenating agent of the positive halogen type, i.e. one capable of halogenating an amidine N atom; and their conversion into 2-R-benzimidazoles by treatment with a base. Suitable halogenating agents include N-haloamides and -imides, and HOCl and HOBr; the latter may be produced in situ from an alkali or alkaline earth metal hypohalite and a hydrohalide of the amidine. Specified valves for R are thiazolyl, isothiazolyl, and 1,2,3-, 1,2,4- and 1,2,5-thiadiazolyl. Solvents may be used in each step. Suitable bases for the production of the benzimidazoles are alkali and alkaline earth metal hydroxides, ammonium hydroxide, trialkylamines and alkali metal alkoxides and hydrides. It is also stated that ring-closure may be effected by irradiation with ultra-violet light. The starting amidine may be prepared by reaction of RCN with aniline or a substituted aniline, with isolation as a hydrohalide. The compounds RCN may be obtained by dehydration with P2O5 of RCONH2, themselves prepared from RCO3H via RCOCl. Reference has been directed by the Comptroller to Specifications 948,635 and 988,784.</p> |
