Phosphine-Catalyzed Sequential [4 + 3] Domino Annulation/Allylic Alkylation Reaction of MBH Carbonates: Efficient Construction of Seven-Membered Heterocycles.

Phosphine-catalyzed intermolecular sequential [4 + 3] domino annulation/allylic alkylation of MBH carbonates and N-tosyl azadienes is reported. A series of functionalized benzofuran-fused seven-membered nitrogen-heterocyclic compounds with one quaternary center were obtained in good to excellent yields. In this sequential reaction, three new bonds were formed in one pot, and the MBH carbonates serve as 1,2,3-C3 synthon and C1 synthon at the same time.