2-Formylpyrroles as Building Blocks in a Divergent Synthesis of Pyrrolizines

The selective functionalization of 2-formylpyrrole to provide diverse 1,2- and 1,2,5-substituted pyrroles is described. These compounds were used as versatile building blocks in a divergent synthesis of biologically valuable aza-bycyclic skeletons, such as pyrrolizine and pyrrolizidine derivatives. These bicycles were prepared following metal-free cascade synthetic approaches via regioselective intramolecular 1,3-dipolar cycloadditions and stereoselective Knoevenagel/Michael/ cyclization­ with dimethyl malonate.