Assembly of the 1-Azaspiro[5.5]undecane Framework Associated with Perhydrohistrionicotoxin via Electrocyclic Ring-Opening of a Ring-Fused gem-Dichlorocyclopropane and Trapping of the Resulting π-Allyl Cation by a Tethered, Nitrogen-Centered Nucleophile

Martin G. Banwell; Florian Vogt; Angela W. Wu

doi:10.1071/CH06218

RESEARCH ARTICLE

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Assembly of the 1-Azaspiro[5.5]undecane Framework Associated with Perhydrohistrionicotoxin via Electrocyclic Ring-Opening of a Ring-Fused gem-Dichlorocyclopropane and Trapping of the Resulting π-Allyl Cation by a Tethered, Nitrogen-Centered Nucleophile

Martin G. Banwell ^A ^C , Florian Vogt ^A and Angela W. Wu ^B

+ Author Affiliations

- Author Affiliations

^A Research School of Chemistry, Australian National University, Canberra ACT 0200, Australia.

^B School of Chemistry, University of Melbourne, Parkville VIC 3052, Australia.

^C Corresponding author. Email: mgb@rsc.anu.edu.au

Australian Journal of Chemistry 59(7) 415-425 https://doi.org/10.1071/CH06218
Submitted: 21 June 2006 Accepted: 24 July 2006 Published: 22 August 2006

Abstract

The carbamate-tethered gem-dichlorocyclopropane 27 was prepared, as a mixture of epimers, in ten steps from commercially available β,γ-unsaturated nitrile 9. Upon treatment with silver acetate under a range of reaction conditions, compound 27 underwent electrocyclic ring opening to give the corresponding π-allyl cation that was then trapped by the reaction solvent, chloride ion, and/or acetate ion, and so affording varying mixtures of the chlorocyclohexenes 28, 29, 30, and/or 31. Sequential treatment of the same substrate with LiHMDS (to generate the conjugate base of this carbamate) then silver tetrafluoroborate afforded the chlorocyclohexadiene 32 as the exclusive product of reaction. No spirocyclization product of the type 3 arising from trapping of the intermediate π-allyl cation by the tethered carbamate was observed under any of the reaction conditions examined. In contrast, analogous treatment of the more rigid system 38 afforded compound 39 incorporating the 1-azaspiro[5.5]undecane framework associated with the potent neurotoxin perhydrohistrionicotoxin (2).

Acknowledgments

We thank the Institute of Advanced Studies and the Australian Research Council for financial support.

References

Assembly of the 1-Azaspiro[5.5]undecane Framework Associated with Perhydrohistrionicotoxin via Electrocyclic Ring-Opening of a Ring-Fused gem-Dichlorocyclopropane and Trapping of the Resulting π-Allyl Cation by a Tethered, Nitrogen-Centered Nucleophile

Abstract

Acknowledgments

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