First synthesis and further functionalization of 7-chloro-imidazo[2,1-b][1,3]thiazin-5-ones

A convenient four-step preparation route to novel 7-chloro-imidazo[2,1-b][1,3]thiazin-5-ones is presented, starting from methyl phenylglyoxylate. A unique feature of this synthesis is a heterocyclization strategy, in which a halogen atom is introduced already during the ring closure. 7-Chloro-6-phenyl-imidazothiazinones with a broad range of various substituents in the phenyl and imidazole moieties are obtainable by this method, as well as different chlorinated triazolothiazinones. The chloro function can be easily replaced in nucleophilic substitution reactions by amino, alkoxy and arylthio groups as well as by a fluoro atom.