Synthesis of spiropyrrolidines and spiropyrrolizidines by 1,3-dipolar cycloadditions of azomethine ylides to substituted α-methylene-γ-lactones

1,3-Dipolar cycloadditions of (E)- and (Z)-substituted α-methylene-γ-lactones with azomethine ylides derived from N-methyl glycine and l-proline gave the corresponding spiropyrrolidine and spiropyrrolizidine cycloadducts in good to moderate yields with various extent of stereoselectivity and regioselectivity. Cycloadditions of the azomethine ylide derived from l-proline exhibited endo selectivity especially in the case of (Z)-isomers of starting methylene lactones. Reactivity and regioselectivity were rationalized by a comparison with quantum chemical calculations (AM1). Structures of derivatives prepared were determined by NMR spectroscopy and by X-ray.