The unexpected and facile molybdenum mediated formation of tri- and tetracyclic pentathiepins from pyrazine-alkynes and sulfur.

The synthesis of a novel family of pentathiepino-pyrrolo[1,2-a]pyrazine derivatives is reported. These compounds are formed by the reaction of alkynyl-substituted heterocyclic precursors with elemental sulfur in the presence of molybdenum oxo bis-tetrasulfide under very mild conditions.