Divergent C3-C4 Bond Cleavage of Spiro β-Lactams for the Switchable Synthesis of 3,3-Disubstituted Oxindoles and 2-Arylacrylamides.

Herein, a visible-light-driven tandem Wolff rearrangement/Staudinger cycloaddition of α-diazoketones with quinone imine ketals (QIKs) is developed, generating spiro β-lactams that undergo divergent C3-C4 bond cleavage under acid or thermal conditions to afford 3,3-disubstituted oxindoles or 2-arylacrylamides, respectively. Extensive mechanistic studies reveal distinct concerted and stepwise pathways. This one-pot, one-step protocol proceeds under mild, metal-free conditions, releasing only N2 and methanol as byproducts, which also provides a rare example of condition-controlled divergent ring manipulation of β-lactams via C3-C4 bond cleavage.