Studies on tandem transesterification and intramolecular cycloaddition of nitrones. 2. Sequential bicyclization of α,α-dialkoxycarbonylnitrones with allyl alcohols

Abstract

Treatment of α,α-alkoxycarbonylnitrones with 1.5 equiv. of allyl alcohols in the presence of 0.1 equiv. of titanium tetrachloride and molecular sieves 4A causes tandem transesterification, E, Z-isomerization of the nitrone moieties, and intramolecular 1,3-dipolar cycloaddition to furnish bicyclic compound having ester group at the bridge head position. These reactions rarely give double transesterification product due to high reactivity of the intermediates as dipolars rather than transesterification reactivity.