Bromine-induced cyclization of 1-acyl-3-(3-thienyl)-2-thioureas to 2-acylaminothieno[3,2-d]thiazoles

Three different 1-acyl-3-(3-thienyl)-2-thioureas were cyclized to 2-acylaminothieno3,2-d]thiazoles with bromine in acetic acid whereas the corresponding 2-thienylthiourea derivatives were brominated under the same reaction conditions. The parent thieno3,2-d]thiazole was prepared by acid hydrolysis and deamination of 2-benzoylaminothieno3,2-d]thiazole. This new heterocyclic compound was nitrated and brominated in the 5-position.