Phosphine-Catalyzed\n[3 + 4] Annulations of Salicylaldehyde\nSchiff Bases with α‑Substituted Allenes: Construction\nof Functionalized Benzoxepine Fused Succinimide Derivatives

Herein we reported a novel strategy for constructing\nbenzoxepine\nfused succinimide derivatives via a phosphine-catalyzed [3 + 4] cyclization\nof α-substituted allenes and salicylaldehyde Schiff bases. This\nmethodology serves as a conduit for the construction of benzoxepine\nderivatives in good yields under mild conditions by an unprecedented\nmode involving the β′-carbon of allenes. Density functional\ntheory calculations were conducted to study the possible mechanism.\nMoreover, this class of compounds exhibited the potential ability\nof cytotoxicity toward cancer cells.