Divergent 4+3 Annulations of β′-Acetoxy Allenoates: Access to Azepino1,2-aindole Derivatives

In this work, the Lewis base-catalyzed divergent 4 + 3 annulation reactions of β′-acetoxy allenoates with two different indole derivatives are reported. A wide range of azepino1,2-aindole derivatives was smoothly obtained from 2-((3-formyl-1H-indol-2-yl)methyl)malonates by employing the DABCO catalyst. The syntheses of two regioselective diazepino1,2-aindole derivatives from 3-formyl-1H-indole-2-carboxamides are realized by the catalysis of DABCO and organophosphine, respectively. A series of functional group transformations can be achieved in the three 1,2-fused seven-membered indole products.