Hidden Heptacyclic Chiral N‐Acyl Iminium Ions: A New Entry to Enantioenriched Polycyclic Azepanes and Azocanes by Superacid‐Promoted Intramolecular Pictet‐Spengler Reaction

• Published in: Chemistry : a European journal Vol. 28; no. 25; pp. e202200432 - n/a
• Main Authors: Reviriot, Yasmin, Michelet, Bastien, Beaud, Rodolphe, Martin‐Mingot, Agnès, Guégan, Frédéric, Thibaudeau, Sébastien, Rodriguez, Jean, Bonne, Damien
• Format: Journal Article
• Language: English
• Published: WEINHEIM Wiley 02.05.2022; Wiley Subscription Services, Inc; Wiley-VCH Verlag
• Subjects: azepane; azocane; Chemical Sciences; Chemistry; Chemistry, Multidisciplinary; Enantiomers; Ions; N-acyliminium ion; Organic chemistry; organocatalysis; Physical Sciences; Science & Technology; Stereoisomerism; Stereoselectivity; superacid; organocatalysis; N-acyliminium ion; superacid; azepane; RULES; azocane; CYCLIZATION; ALKALOIDS
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202200432

Enantioenriched complex fused‐tricyclic azepanes or bridged‐polycyclic azocanes were constructed via a two‐step sequence involving an enantioselective organocascade followed by superacid activation of the domino adduct. The activated oxa‐bridged azepane acts as a key hidden heptacyclic chiral N‐acyl iminium ion triggering a chemo‐ and diastereoselective intramolecular mono‐ or di‐arylation. The combination of enantioselective organocatalysis and superacid activation allows for the construction of enantioenriched complex fused‐tricyclic azepanes or bridged‐polycyclic azocanes from simple acyclic substrates. The hidden heptacyclic chiral N‐acyl iminium ion is generated by superacid activation and is the key intermediate that triggers a chemo‐ and diastereoselective intramolecular mono‐ or di‐arylation.