Regio- and Stereoselective Multicomponent Synthesis of Novel Chromeno-Annulated Pyrrolizine and Thiazolizine Scaffolds via 1,3-Dipolar Cycloaddition Reactions

An efficient protocol for the construction of chromeno annulated pyrrolizine and thiazolizines derivatives through an in-situ formation of an azomethine ylides and zwitterionic intermediate followed by 1,3-dipolar cycloaddition reaction is described. This novel one-pot reaction paves the way for the successful assembly of salicaldehydes, dialkyl acetylenedicarboxylates and L-proline or thiazolidine-4-carboxylic acid in the presence of a basic catalyst. This domino process affords polycyclic chromeno annulated pyrrolizines and chromenothiazolizines in good yields.