Syntheses, addition–eliminations, and addition–displacements of 5-(bromomethylene)hydantoins

5-(Bromomethylene)hydantoins, prepared from bromopyruvic acid and ureas in the presence of BF3, react with various nitrogen, phosphorus, sulfur, and carbon nucleophiles by addition–elimination to give the corresponding 5-(substituted-methylene)hydantoins. The 5-(bromomethylene)hydantoins also undergo acid-catalyzed reactions with nucleophiles by addition–displacement and addition–elimination processes.