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[cd]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.
Catalytic Asymmetric Reactions of 4-Substituted Indoles with Nitroethene: A Direct Entry to Ergot Alkaloid Structures / Romanini, Simone; Galletti, Emilio; Caruana, Lorenzo; Mazzanti, Andrea; Himo, Fahmi; Santoro, Stefano; Fochi, Mariafrancesca; Bernardi, Luca. - In: CHEMISTRY-A EUROPEAN JOURNAL. - ISSN 0947-6539. - STAMPA. - 21:49(2015), pp. 17578-17582. [10.1002/chem.201502655]
Catalytic Asymmetric Reactions of 4-Substituted Indoles with Nitroethene: A Direct Entry to Ergot Alkaloid Structures
CARUANA, LORENZO;MAZZANTI, ANDREA;FOCHI, MARIAFRANCESCA
;BERNARDI, LUCA
2015
Abstract
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[cd]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.File | Dimensione | Formato | |
---|---|---|---|
numero 74 Chem EJ 2015 ergot COMPLETO.pdf
accesso aperto
Descrizione: PDF editoriale + Supporting information file
Tipo:
Versione (PDF) editoriale
Licenza:
Licenza per Accesso Aperto. Creative Commons Attribuzione - Non commerciale - Non opere derivate (CCBYNCND)
Dimensione
6.18 MB
Formato
Adobe PDF
|
6.18 MB | Adobe PDF | Visualizza/Apri |
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.