Exploring Cyclization Strategies to Access Stemona Alkaloids: Subtle Effects Influencing Reactivity in Intramolecular Michael Additions

This report investigates the fundamental basis for rather surprising patterns of reactivity in Brønsted acid-mediated cyclizations of pyrrole substrates bearing pendant Michael acceptors that were identified during syntheses of Stemona alkaloids. Integrated experimental and theoretical studies revea...

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Bibliographic Details
Published in:Organic letters 2021-11, Vol.23 (21), p.8494-8498
Main Authors: Olivier, Wesley J, BabaAhmadi, Rasool, Lucas, Nigel T, Ariafard, Alireza, Bissember, Alex C, Smith, Jason A
Format: Article
Language:English
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Summary:This report investigates the fundamental basis for rather surprising patterns of reactivity in Brønsted acid-mediated cyclizations of pyrrole substrates bearing pendant Michael acceptors that were identified during syntheses of Stemona alkaloids. Integrated experimental and theoretical studies reveal the profound influence that substituent effects have on the viability of these transformations. Additionally, we identify that electronic effects, in addition to barrier-lowering secondary orbital interactions within transition states, account for the exclusive preference for 7-endo-trig cyclizations over 6-exo-trig cyclizations.
ISSN:1523-7060
1523-7052
DOI:10.1021/acs.orglett.1c03205