A synthesis of functionalized dihydro-1Η-pyrrolizines and spiropyrrolizines via [2 + 3] cycloaddition reactions.

A one-pot synthesis of dihydro-1H-pyrrolizine derivatives via [Formula: see text] cycloaddition reaction of azomethine ylides, prepared in situ from proline and ninhydrin, with dialkyl acetylenedicarboxylates, in alcohols, is described. When sarcosine was used instead of proline, functionalized spiropyrrolizines were obtained. Under these conditions, alkyl propiolates produced stable spirans.