Bench‐Stable Boryl Thianthrenium Dication Enables Aziridinyl Boronate Synthesis via Metal‐Free Late‐Stage Aziridination with Diverse Nitrogen Nucleophiles

Abstract Organoboron compounds are indispensable in modern organic synthesis and biomedical research. This study describes the synthesis of bench‐stable boryl thianthrenium dicationic compound via chemical or electrochemical thianthrenation of vinyl MIDA boronate. This unique boryl thianthrenium dication enables a transition‐metal‐free, chemo‐, and diastereoselective synthesis of aziridinyl boronates, utilizing a broad range of nitrogen nucleophiles. The method demonstrates generality, practicality, and functional group tolerance, as evidenced by its application to diverse substrates, including the late‐stage modification of drug molecules. Notably, the MIDA boryl group plays crucial roles in this approach including i) suppressing undesired deborylation, ii) promoting exclusive mono‐adduct formation via a formal 4 + 2 cycloaddition pathway, iii) directing regioselective vinyl boryl thianthrenium formation via selective deprotonation, and iv) enabling diastereoselective aziridination. The strategic significance of this approach is further highlighted through electrochemical one‐pot protocol, asymmetric synthesis using vinyl PIDA boronate, and diverse downstream transformations of aziridinyl boronates, offering new opportunities for synthetically challenging boron‐containing drug‐like scaffolds.