Nickel-catalyzed sequential 1,2-N-migration/BCBs ring-opening to access spirocyclobutyl β-amino acid esters

Hetero-atom migration strategy is a powerful tool to access complex molecules. Herein, we disclose a cascade radical 1,2-N-migration/ring-opening of N-aryl bicyclobutyl amides (BCBs) with β-bromo α-amino acid esters by cooperative Ni/diboron catalysis, which afforded a wide array of spirocyclobutyl oxindoles tethering a β-amino acid motif under room temperature conditions. The method suppressed the typical intramolecular C(sp2)-H cyclization of β-bromo amino acid esters after 1,2-N-migration, successfully incorporating β-amino acid moieties into the spirocyclobutyl oxindole scaffolds.