Synthesis of vinyl- azetidines and beta-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 general 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 co-catalyst, 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 allylamino unit, and are prepared at room temperature with complete atom-economy. The utility of the method is showed by further downstream derivatization.