Stereoselective synthesis of 5-(41-azetidinyl)-proline esters via 1,3-dipolar cycloaddition reaction of N-metalated azomethine ylides

The conformationally locked s-trans enone functionality present in the (E)-3-arylidene-4-chromanones undergo regioselective 1,3-dipolar cycloaddition reaction with N-metalated azomethine ylides derived from β-lactam imines of glycine methyl ester in the presence of silver acetate to give spiropyrrolidines in moderate to good yield. The regio and stereochemistry of the cycloadducts have been established by single crystal X-ray structure and spectroscopic techniques.