Reactions of 1,2,4,5-tetrazines with S-nucleophiles

The reactions of 3,6-disubstituted and azoloannulated 1,2,4,5-tetrazines containing heterocyclic leaving groups with S-nucleophiles were studied. The methods of introduction of functionalized thiols, including thiol derivatives of 1,7- and 1,2-dicarba-closo-dodecaboranes, into the tetrazine ring were developed. It was established for the first time that, instead of replacement of a leaving group in the tetrazine ring, the attack of S-nucleophile at the unsubstituted carbon atom occurs in the case of imidazo[1,2-b][1,2,4,5]tetrazines to form previously unknown products of nucleophilic substitution of the hydrogen atom.