Halogen migration and amination in reactions of halogeno derivatives of five‐membered hetarenes with potassium amide in liquid ammonia

On treatment of 2‐bromothiophene, 2,3‐, 2,4‐, and 2,5‐dibromothiophene with potassium amide in liquid ammonia at − 75°, a bromine migration of position α to position β of the thiophene ring takes place. On treatment of the above mentioned compounds with potassium amide in liquid ammonia at − 33°, besides α to β bromine rearrangement, amination to 3‐aminothiophene was observed. The mechanism of the transbromination is assumed to be an intermolecular process, involving dibromo‐ and tribromo‐thiophenes. The formation of 3‐aminothiophene does not occur via a didehydro intermediate, but it is the result of amination of a polybromothiophene, yielding an amino‐bromothiophene, which is debrominated by reaction with amide ion or a thiophene anion.