Catalytic Staudinger–Aza-Wittig Reactions through Cycling between a Stibinidene and Isolable Iminostibanes: Chemoselectivity Achieved by Suppressing the Staudinger Reduction

Main-group compounds featuring multiple bonds with heavy elements exhibit unusual bonding, diverse structures, and rich reactivity that could activate various small molecules. However, the regeneration of such highly active species in a catalytic cycle poses significant challenges, thereby restricting their applications in catalysis. Herein, we report on the synthesis of iminostibanes stabilized by an N,C,N-pincer ligand bearing polar SbIII═N double bonds through the reactions of the corresponding stibinidene with organic azides. Experimental observations and computational studies demonstrate that intramolecular donor → Sb interactions provided by the pincer ligand play a crucial role in stabilizing the iminostibanes. Meanwhile, it is essential for iminyl groups to incorporate electron-withdrawing groups capable of accepting electron delocalization or bulky substituents offering steric protection. The synthetic reactions of iminostibanes are successfully applied to both catalytic Staudinger reduction and Staudinger–aza-Wittig reactions. We can control the divergent catalysis through choosing appropriate reductants. Mechanistic investigations prove that iminostibanes serve as crucial intermediates in both types of catalysis.