α‐Iminopyridine–Derived 1,3,2‐Diazaborole Borenium Ions: Synthesis, Reduction, and Addition Reaction

While boron cation chemistry has been extensively explored in recent years, the integration of boron cations and redox‐active ligands remains relatively underdeveloped. In this study, α‐iminopyridine‐derived 1,3,2‐diazaborole borenium cations featuring IMe 4 , IMes, and cAAC ligands were investigated. Among this series, the IMe 4 ‐coordinated borenium ion ([ 4 ] + ) exhibits the most pronounced ligand‐based reactivity, including ligand‐centered reduction to a neutral boryl radical ( 7 • ), tandem cycloaddition‐rearrangement reaction with benzaldehyde to afford a syn ‐selective 1,3,2‐oxazaborolidinium ([ 10 ] + ), and TMS‐OTf–catalyzed transfer hydrogenation with ammonia‐borane to generate a hydridoboronium ion ([ 11 ] + ).