Regiochemistry in the Intramolecular Cycloadditions of Substituted 5-Alkenyl and 6-Alkenyl Nitrones

Article abstract of DOI:10.1021/jo00223a003

A series of 5-alkenyl and 6-alkenyl aldehydes bearing aryl and ester functionality on the alkene and with and without 1,3-dioxolane substitution at the 3-position has been prepared.The N-methyl and N-benzyl nitrones derived by the condensation of the aldehydes with the corresponding hydroxylamines undergo intramolecular 1,3-dipolar cycloaddition on heating (or at room temperature in two instances) to give either bridged or fused isoxazolidines depending on the regiochemistry of the cycloaddition reaction.The 6-alkenyl nitrones give fused products in all cases except those bearing an aryl group at C-6, which give bridged products.All of the 5-alkenyl nitrones prepared in this study cyclized to afford fused isoxazolidines.