A facile one-step approach to generate annulated indoles from (N-H) indoles and dibromoalkanes was developed based on palladium-catalyzed norbornene-mediated regioselective C-H activation and subsequent cyclization. The reaction is compatible with various indole substituents, as well as a range of simple and functionalized dibromoalkyl reagents. The detailed reaction mechanism was investigated by a series of synthetic and mechanistic studies, as well as NMR spectroscopic analyses. The results indicate that the catalytic cycle consists of initial C2-alkylation of indoles that is followed by N-alkylation or an intramolecular nucleophilic substitution/isomerization cascade to yield, respectively, [<i>a</i>]- or [<i>b</i>]-annulated indoles.

One-step approach to generate annulated indoles through a palladium-catalyzed norbornene-mediated cascade reaction

2019 Spring National Meeting

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