On the stereoselective bicyclization of aminodienes catalyzed by chelating diamide complexes of the group 3 metals. A direct comparison of Sc(III) and Y(III) bis(amide)s with an application to the synthesis of alkaloid 195F

Highly diastereoselective bicyclizations of aminodienes catalyzed by chelating diamide complexes of Sc(III) and Y(III) that lead to pyrrolizidines and indolizidines are described. This bis(annulation) procedure has been utilized in a concise synthesis of the pyrrolizidine alkaloid 195F.