“Addition–Elimination” Transformations for Aminative Isomerization of Bicyclo[1.1.0]butanes (BCBs)

This work discloses a novel aminative isomerization of bicyclo[1.1.0]butanes (BCBs) for the synthesis of functionalized cyclobutenes in which the C═C bond is directly adjacent to the ester group, a previously inaccessible constitutional isomer. The transformation employs sulfonyl sulfur diimides as amination reagents under catalyst-free and mild conditions. Mechanistic studies support an addition-elimination pathway involving a formal [2π+2σ] cycloaddition followed by intramolecular elimination and deprotection.