This work discloses a novel aminative isomerization of bicyclo1.1.0butanes (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.
Yang et al. (Mon,) studied this question.