Addition of selenium dibromide to divinyl sulfide: spontaneous rearrangement of 2,6-dibromo-1,4-thiaselenane to 5-bromo-2-bromomethyl-1,3-thiaselenolane

Synthesis of the novel selenium heterocycles 1, 2, and 3 based on the addition reaction of selenium dibromide to divinyl sulfide is described. The reaction proceeded in CCl4 at room temperature to give the thiaselenane 1. Even at low temperature in chloroform solution, the 6-membered thiaselenane 1 underwent spontaneous rearrangement to the 5-membered thiaselenolane 2. In turn, the thiaselenolane 2 underwent spontaneous dehydrobromination to the thiaselenole 3 in chloroform.