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.