These compounds are represented by formula I, wherein n is 1 or 2 and R is a lower alkyl, loweralkenyl or lower cycloalkyl, such as methyl, ethyl, isopropyl, cyclopropyl and vinyl, as well as the pharmaceutically acceptable acid addition salts thereof. ##STR2##Compounds I may be conveniently prepared by means of a N-alkylation reaction of a N-unsubstituted benzimidazole represented by the general