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

Azetidines and beta-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 beta-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.