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Accessing Skeletal Diversity under Iron Catalysis using Substrate Control: Formation of Pyrroles versus Lactones

Authors

  • Benito Alcaide,

    Corresponding author
    1. Grupo de Lactamas y Heterociclos Bioactivos, Departamento de Química Orgánica I, Unidad Asociada al CSIC, Facultad de Química, Universidad Complutense de Madrid, 28040 Madrid, Spain, Fax: (+34)-91-394-4103
    • Grupo de Lactamas y Heterociclos Bioactivos, Departamento de Química Orgánica I, Unidad Asociada al CSIC, Facultad de Química, Universidad Complutense de Madrid, 28040 Madrid, Spain, Fax: (+34)-91-394-4103
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  • Pedro Almendros,

    Corresponding author
    1. Instituto de Química Orgánica General, Consejo Superior de Investigaciones Científicas, CSIC, Juan de la Cierva 3, 28006 Madrid, Spain, Fax: (+34)-91-564-4853
    • Instituto de Química Orgánica General, Consejo Superior de Investigaciones Científicas, CSIC, Juan de la Cierva 3, 28006 Madrid, Spain, Fax: (+34)-91-564-4853
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  • M. Teresa Quirós

    1. Grupo de Lactamas y Heterociclos Bioactivos, Departamento de Química Orgánica I, Unidad Asociada al CSIC, Facultad de Química, Universidad Complutense de Madrid, 28040 Madrid, Spain, Fax: (+34)-91-394-4103
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Abstract

2-Azetidinone-tethered alkynols and allenols, readily prepared from a propanylidene β-lactam aldehyde, were used as starting materials for divergent ring expansion reactions catalyzed by iron(III) chloride. Worthy of note, in contrast to the iron-catalyzed reactions of β-lactam allenols which lead to γ-lactones, the reaction of β-lactam alkynols under identical conditions gives pyrroles. The gold-catalyzed 6-endo aminocyclization of these allenic γ-lactones formed fused dihydropyridines. The iron-catalyzed formation of pyrroles may proceed through a Meyer–Schuster rearrangement followed by β-lactam ring opening and cyclization by attack of the amino group to the ketone.

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