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

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

References and Notes

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1

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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] ).