For the synthesis of novel thiazolo[3,2-a]benzimidazol-3-ones and thiazolo[3,2-a]benzimidazoles, two methods have been developed which afforded the target compounds in relatively good yields by a pot process. The reaction between 2-mercapto-1H-benzimidazoles, acetophenone derivatives and 4-methylcyclohexanone in acid medium gave the tricyclic and tetracyclic benzimidazole compounds. We have also studied the flexibility of the position-7 of the thiazolobenzimidazoles by introducing the nitro and the methyl group. All compounds were characterized by means of