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Convenient access to 5-membered cyclic iminium ions: evidence for a stepwise [4 + 2] cycloaddition mechanism

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Abstract

In situ generation and reaction of novel 5-membered N-tosyl cyclic α,β-unsaturated iminium ions from readily prepared stable precursors is demonstrated. Formal iminium Diels–Alder cycloaddition proceeded in good yield via a stepwise rather than concerted cycloaddition process, confirmed through the isolation of a Mukaiyama–Michael type intermediate. Relative stereochemistry was determined upon subsequent intramolecular cyclisation under Lewis acid catalysis to afford formal endo 5,6-spirobicyclic adducts, as confirmed by crystallography. Further synthetic elaboration towards complex molecular scaffolds based on the dinoflagellate metabolite portimine, a potent apoptosis inducer, were also developed.

Graphical abstract: Convenient access to 5-membered cyclic iminium ions: evidence for a stepwise [4 + 2] cycloaddition mechanism

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Publication details

The article was received on 01 Feb 2019, accepted on 08 Feb 2019 and first published on 11 Feb 2019


Article type: Paper
DOI: 10.1039/C9OB00262F
Citation: Org. Biomol. Chem., 2019, Advance Article

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    Convenient access to 5-membered cyclic iminium ions: evidence for a stepwise [4 + 2] cycloaddition mechanism

    J. L. Freeman, M. A. Brimble and D. P. Furkert, Org. Biomol. Chem., 2019, Advance Article , DOI: 10.1039/C9OB00262F

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