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.

Dearomative cycloadditions of a silylene with pyrazine and quinoxaline.

The dearomative cycloaddition of a silylene with pyrazine provides a disilicon and dinitrogen analogue of cis,cis,trans-1,3,6-cyclooctatriene 2 as a purple solid. Compound 2 has a twisted and pyramidalised trans-alkene moiety. The HOMO → LUMO [n(N) → π*(N[double bond, length as m-dash]C-C[double bond, length as m-dash]N)] transition band of 2 appeared at 525 nm in a hexane solution.