STUDIES ON TANDEM TRANSESTERIFICATION AND INTRAMOLECULAR CYCLOADDITION OF NITRONES .2. SEQUENTIAL BICYCLIZATION OF ALPHA,ALPHA-DIALKOXYCARBONYLNITRONES WITH ALLYL ALCOHOLS

Treatment of alpha,alpha-alkoxycarbonylnitrones with 1.5 equiv. of all yl alcohols in the presence of 0.1 equiv. of titanium tetrachloride an d molecular sieves 4A causes tandem transesterification, E,Z-isomeriza tion of the nitrone moieties, and intramolecular 1,3-dipolar cycloaddi tion to furnish bicyclic compound having ester group at the bridge hea d position. These reactions rarely give double transesterification pro duct due to high reactivity of the intermediates as dipolars rather th an transesterification reactivity.