The synthesis of a series N-(4-piperidinyl)-lH-benzimidazol-2-amines and the preliminary evaluation of their in vitro and in vivo antihistaminic activity are described. Cyclodesulfurization of (2-aminopheny1) thioureas with mercury (I1) oxide resulted in 2- aminobenzimidazole intermediates, which were monoalkylated on the endo-nitrogen atom. After deprotection of the piperidine nitrogen atom with 48% aqueous hydrobromic acid ...