Diastereo- and Enantioselective Construction of Dihydrobenzo[<i>e</i>]indole Scaffolds via Catalytic Asymmetric [3 + 2] Cycloannulations

The first catalytic asymmetric construction of chiral dihydrobenzo­[e]­indole scaffolds has been established in a highly diastereo- and enantioselective mode (30 examples, up to 99% yield, >95:5 dr, >99% ee), which makes use of chiral phosphoric acid-catalyzed [3 + 2] cycloannulations of azonaphthalene derivatives with 3-vinylindoles. This reaction also represents the first catalytic asymmetric cycloannulation of azonaphthalene derivatives with alkenes, which will not only provide a useful method for constructing enantioenriched dihydrobenzo­[e]­indole scaffolds but also advance the chemistry of catalytic asymmetric reactions of azonaphthalene derivatives.