Base mediated 5-endo-dig cyclization of N-propargyl proline derivatives: A facile entry to pyrrolizidine scaffolds

Abstract

A simple, base facilitated 5-endo-dig cyclization strategy has been exploited for the assembly of bicyclic core of pyrrolizidine alkaloids. This unprecedented protocol allows access to a diverse range of alkyl and aryl substituted pyrrolizidine scaffolds in moderate yields from readily available N-propargyl-L-proline ester derivatives under mild conditions. No catalyst or alkyne activator is required to effect this atom economical transformation.