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

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.