The cyclodesulphurization of thio-compounds. Part 12: A new simple method for the synthesis of N-alpha-substituted benzimidazoles from thiourea derivatives.

A new facile method has been established for the synthesis of N-alpha-substituted benzimidazoles by cyclodesulphurization of various N-[2-amino]-phenyl-N'-alkyl, -aryl and -aralkylthiourea derivatives with mercuric salts. Besides mercuric chloride, the use of mercuric oxide and mercuric acetate was successful for the first time in effecting ring closure of thio-compounds. The attempted use of acid condensing agents showed phosphoryl chloride to be less efficient than mercuric salts in conducting the cyclization reactions and led to poor yields of cyclized products.