The Synthesis of Spirooxindole Pyrrolidines via an Asymmetric Azomethine Ylide [1,3]-Dipolar Cycloaddition Reaction

The asymmetric [1,3] dipolar cycloaddition reactions of azomethine ylides derived from 5,6-diphenylmorpholin-2-one with various aldehydes and ethyl oxindolylideneacetate are described.Addition of an aldehyde to the morpholin-2-one, under essentially neutral conditions, results in the preferential formation of the E-ylide which then reacts with the dipolarophile to yield spirooxindole pyrrolidine derivatives in moderate to excellent regio-and diastereoselectivities.The resulting cycloadducts were easily separated by column chromatography and converted to the corresponding amino acid methyl esters through catalytic hydrogenolysis.