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Synlett 2006(14): 2329-2333  
DOI: 10.1055/s-2006-949637
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© Georg Thieme Verlag Stuttgart · New York

Concerning Lewis Acid Promoted, Directing-Group-Free Epoxide-Ring-Opening Cascades

Timothy P. Heffron, Timothy F. Jamison*
Massachusetts Institute of Technology, Department of Chemistry, Cambridge, MA 02139, USA
Fax: +1(617)3240253; e-Mail: tfj@mit.edu;
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Publication History

Received 2 May 2006
Publication Date:
24 August 2006 (online)

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Abstract

Lewis acid promoted cascades of a tris(disubstituted epoxide) triggered by silver-promoted abstraction of a bromide ion favors trans-dioxabicyclo[4.3.0]nonanes, rather than diads or triads of tetrahydropyrans (trans-dioxabicylco[4.4.0]decanes, for example). These results suggest that an epoxide-attacking-epoxonium mechanism is not operative in this system.

Key words

epoxides - cascade - ring opening - fused-ring systems - Lewis acids

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1

Current address: Genentech Inc., 1 DNA Way, South San Francisco, CA 94080, USA.

8

It should be noted that McDonald observed that the cis/trans selectivity also strongly depends on the nature of the trapping nucleophile (a carbamate in the example shown in Scheme [7] ).