A Retro-Staudinger Cycloaddition: Mechanochemical Cycloelimination of a β‑Lactam Mechanophore

Mechanical
activation of a β-lactam mechanophore using ultrasound
induces a formal [2 + 2] cycloelimination reaction producing ketene
and imine functional groupsthe reverse reaction of the Staudinger
cycloaddition. This transformation is predicted by computational modeling
and verified by kinetics and UV–vis absorption measurements
as well as polymer end-group analysis using 1H and 13C NMR spectroscopy. Addition of the β-lactam motif
to the current repertoire of covalent mechanophores coupled with the
diverse reactivity of the ketene functional group provides a promising
new platform for achieving materials capable of autonomic self-healing
behavior in response to external forces.