Switching Selectivity of α‑Enolic Dithioesters: One Pot Access to Functionalized 1,2- and 1,3-Dithioles

An
operationally simple cascade protocol has been developed for
the construction of 1,2- and 1,3-dithiole derivatives from α-enolic
dithioesters. 1,2-Dithioles are achieved by the reaction of dithioesters
with elemental sulfur in the presence of InCl3 under solvent-free
conditions. 1,3-Dithioles have been constructed via DABCO mediated
self-coupling of dithioesters in open air enabling the formation of
two new C–S bonds and one ring in a single operation in contiguous
fashion. The reactions proceeded smoothly affording the desired sulfur-rich
heterocycles in good to excellent yields, exhibiting gram-scale ability
and broad functional group tolerance utilizing easy to handle cheap
and easily available reagents. The probable mechanisms for the formation
of 1,2- and 1,3-dithioles from α-enolic dithioesters have been
suggested.