Facile Construction of Tetrahydropyrrolizines by Iron-Catalyzed Double Cyclization of Alkene-Tethered Oxime Esters with 1,2-Disubstituted Alkenes.

The iron-catalyzed cycloaddition reaction of alkene-tethered oxime esters with 1,2-disubstituted alkenes afforded tetrahydropyrrolizines, the structural motif often seen in bicyclic alkaloids. The reaction proceeds through consecutive cycloaddition reactions. These include, first, intramolecular cyclization, followed by intermolecular cyclization with a 1,2-disubstituted alkene in a regioselective manner where an imine moiety first generated plays a pivotal role.