Acid activation of (H ⁺ –K ⁺ )-ATPase inhibiting 2-(2-pyridylmethyl-sulphinyl)benzimidazoles: isolation and characterization of the thiophilic ‘active principle’ and its reactions

2-(2-Pyridylmethylsulphinyl)benzimidazoles rearrange in acid to thiophilic benzimidazo[1,2-b]pyrido[1,2-d][1,2,4]thiadiazinium salts which react with 2-mercaptoethanol forming 2-pyridinio-benzimidazolides.