Organic Letters
Organic Letters
4 years ago

[ASAP] Palladium-Catalyzed, Enantioselective (3 + 2)-Cycloannulation of ß-Keto Esters with Alkylidene 2H-Indoles toward Complex Indole-Based Heterocycles

[ASAP] Palladium-Catalyzed, Enantioselective (3 + 2)-Cycloannulation of ß-Keto Esters with Alkylidene 2H-Indoles toward Complex Indole-Based Heterocycles
Fabian Göricke, Christoph Schneider
A cooperative approach toward biologically important N-fused polycyclic indoles with synthetically challenging tetracyclic [6–5–5–6] and [6–5–5–5] core structures has been developed. The concept is based on a highly stereoselective (3 + 2)-cycloannulation of chiral metal enolates with a reactive vinylogous iminium ion, both generated in situ via dual activation with a single chiral Pd catalyst (5 mol %). Densely functionalized pyrrolo[1,2-a]indoles with three contiguous chiral centers were constructed with high stereoselectivities (>95:5 d.r. and up to >99% ee) and excellent yields (up to 99%). ESI-MS studies and additional control experiments provided a clear mechanistic picture of the cycloannulation event. The products were readily transformed into an array of valuable, indole-based, highly complex heterocycles. The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.orglett.0c02166. ESI-MS studies, control experiments, experimental procedures, compound characterization, NMR spectra, and HPLC chromatograms (PDF) This article has not yet been cited by other publications.

Publisher URL: http://feedproxy.google.com/~r/acs/orlef7/~3/thU0Mr9rIHE/acs.orglett.0c02166

DOI: 10.1021/acs.orglett.0c02166

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