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‐acylaminothieno[3,2‐d]thiazoles with bromine in acetic acid whereas the corresponding 2‐thienylthiourea derivatives were brominated under the same reaction conditions. The parent thieno[3,2‐d]thiazole was prepared by acid hydrolysis and deamination of 2‐benzoylaminothieno[3,2‐d]thiazole. This new heterocyclic compound was nitrated and brominated in the 5‐position.