Synthesis of Vinyl Azetidines and β‑Lactams from Allenamides via Energy-Transfer Relay

Azetidines and β-lactams
are useful and versatile building
blocks with ample synthetic applications and pharmaceutical uses.
However, few catalytic methods provide densely functionalized monocyclic
derivatives, and none could easily afford both azetidines and β-lactams.
Herein, we solved this issue with allenamides. The challenging substrates
were activated by energy transfer combining a tailor-made Ir(III)
complex and a binaphthyl cocatalyst, which acts as a triplet-state
relay and stabilizes intermediates via dispersion interactions. A
triplet intermediate with a vinyl-radical character gives the strained
heterocycles upon 1,5 hydrogen atom transfer. Products have a congested
all-carbon quaternary center and a useful allylamine unit and are
prepared at room temperature with complete atom economy. The utility
of the method is shown by further downstream derivatization.