In connection with the abnormal reaction of ethyl 1-methyl-2-benzimidazolecarboxylate 3- oxide (1) with piperidine, aminolyses of several related esters were investigated. The esters: 1, 2-ethoxycarbonyl-1, 3-dimethylbenzimidazolium iodide (11), 2-methoxycarbonylmethyl-1, 3-dimethylbenzimidazolium iodide (17), ethyl 2-benzothiazolecarboxylate 3-oxide (26) and 2-ethoxycarbonyl-3-methylbenzothiazolium perchlorate (34) under went abnormal ...