Catalytic Asymmetric Reactions of 4-Substituted Indoles with Nitroethene: A Direct Entry to Ergot Alkaloid Structures
Number of Authors: 8
2015 (English)In: Chemistry - A European Journal, ISSN 0947-6539, E-ISSN 1521-3765, Vol. 21, no 49, 17578-17582 p.Article in journal (Refereed) Published
A domino Friedel-Crafts/nitro-Michael reaction between 4-substituted indoles and nitroethene is presented. The reaction is catalyzed by BINOL-derived phosphoric acid catalysts, and delivers the corresponding 3,4-ring-fused indoles with very good results in terms of yields and diastereo- and enantioselectivities. The tricyclic benzo[c-d] indole products bear a nitro group at the right position to serve as precursors of ergot alkaloids, as demonstrated by the formal synthesis of 6,7-secoagroclavine from one of the adducts. DFT calculations suggest that the outcome of the reaction stems from the preferential evolution of a key nitronic acid intermediate through a nucleophilic addition pathway, rather than to the expected quenching through protonation.
Place, publisher, year, edition, pages
2015. Vol. 21, no 49, 17578-17582 p.
asymmetric synthesis, Bronsted acids, indoles, nitroalkenes, organocatalysis
IdentifiersURN: urn:nbn:se:su:diva-125787DOI: 10.1002/chem.201502655ISI: 000367185700006PubMedID: 26486074OAI: oai:DiVA.org:su-125787DiVA: diva2:897993