Sulfur and Oxygen Transfer Reactions with Simultaneous NHC-Coordination from Cyclic Thioureas and Ureas to a Stable Silylene

Reactions of cyclic thioureas (1,3,4,5-tetramethylimidazol-2-thione and 1,3-dimethylimidazolidin-2-thione) and ureas (1,3,4,5-tetramethylimidazol-2-one and 1,3-dimethylimidazolidin-2-one) with an isolable dialkylsilylene were examined. In these reactions, cyclic thioureas served as sulfur and NHC (N-heterocyclic carbene) sources, and the corresponding silanethione and NHC-derived products formed via silanethione-NHC complexes. Reactions of cyclic ureas with the silylene afforded a new NHC and an isolable azomethine ylide. These reactions involved oxygen atom transfer and 1,3-silyl migrations, which were supported by computational studies.