The synthesis of spirooxindole pyrrolidines via an asymmetric azomethine ylide [1,3]-dipolar cycloaddition reaction

Abstract

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.