Ring‐Opening of 1,3‐Imidazole Based Mesoionic Carbenes (iMICs) and Ring‐Closing Clicks: Facile Access to iMIC‐Compounds

Abstract

Herein, ring‐opening of mesoionic carbenes (iMICs) (iMIC=[ArC{N(Dipp)}2C(SiMe3)C:) (Dipp=2,6‐iPr2C6H3, Ar=Ph, 4‐Me2NC6H4 or 4‐PhC6H4) based on an 1,3‐imidazole scaffold to yield N‐ethynylformimidamide (eFIM) derivatives as crystalline solids (eFIM={(Dipp)N=C(Ar)N(Dipp)}C≡CSiMe3) is reported. eFIMs are thermally stable under inert gas atmosphere and show moderate air stability (t1/2=3 h for Ar=Ph). eFIMs are excellent surrogates of iMICs, which generally have a limited shelf‐life, and readily undergo ring‐closing click reactions with a variety of main‐group as well as transition metal Lewis acids to form hitherto challenging iMIC‐compounds in good to excellent yields. In addition to the relevance of eFIMs in the synthesis of iMIC‐compounds, quantification of the stereoelectronic properties of a representative iMIC (Ar=Ph) by experimental and theoretical methods suggests remarkably σ‐donor property and steric profile of these new ligand sets.