Catalytic Macrocyclizations of Thietanes and Thiiranes by Metal Carbonyl Complexes

This Account summarizes our recent studies of the catalytic transformations of thietanes and thiiranes by metal carbonyl complexes of the third row of the transition elements. The goal of the work has been to prepare polythioether macrocycles (thiacrowns) catalytically. This has been achieved with high success for certain thietane reactions. Thiiranes, on the other hand, tend to yield macrocyclic polydisulfides, but it has recently been found that these reactions can be redirected toward the thiacrown products by using certain alkyne carboxylates as cocatalysts. Vinylthiiranes are transformed into 3,6-dihydro-1,2-dithiins catalytically in excellent yield via W(CO)(5)(vinylthiirane) complexes.