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.