Modular Synthesis of Azines Bearing a Guanidine Core from N‐Heterocyclic Carbene (NHC)‐Derived Selenoureas and Diazo Reagents.

N‐Heterocyclic carbene (NHC)‐derived selenoureas comprise a fundamentally important class of NHC derivatives, with key applications in coordination chemistry and the determination of NHC electronic properties. Considering the broad reactivity of chalcogen‐containing compounds, it is surprising to note that the use of NHC‐derived selenoureas as organic synthons remains essentially unexplored. The present contribution introduces a novel, straightforward transformation leading to azines bearing a guanidine moiety, through the reaction of a wide range of NHC‐derived selenoureas with commercially available diazo compounds, in the presence of triphenylphosphine. This transformation offers a new approach to such products, having biological, materials chemistry, and organic synthesis applications. The guanidine‐bearing azines are obtained in excellent yields, with all manipulations taking place in air. A reaction mechanism is proposed, based on both experimental mechanistic findings and density functional theory (DFT) calculations. A one‐pot, multicomponent transesterification reaction between selenoureas, α‐diazoesters, alcohols, and triphenylphosphine was also developed, providing highly functionalized azines. [ABSTRACT FROM AUTHOR]