Synthesis of (-)-209I and (-)-223J

Significance

Piperidines and indolizidines provide the core of many biologically active natural products and pharmaceutical drugs. Previous methodology by Charette has involved the formation of dihydropyridinium salts from a Grob fragmentation using a stoichiometric amount of an expensive silver salt. The above work demonstrates a silver-free process via the use of an O-triflyl intermediate (H) to generate such species, with the synthesis of natural products (-)-209I and (-)-223J showcasing this methodology.