Asymmetric [3+2] Cycloaddition of 3-Amino Oxindole-Based Azomethine Ylides and α,β-Enones with Divergent Diastereocontrol on the Spiro[pyrrolidine-oxindoles]

A general and practical organocatalytic asymmetric 1,3-dipolar cycloaddition of 3-amino oxindole-based azomethine ylides and alpha,beta-enones has been developed. This reaction delivered spiro[pyrrolidine-2,3'-oxindole] products in high yields with excellent regio- and enantioselectivities (up to 99% yield, >20:1 rr, 99% ee). In addition, an array of spiro[dihydropyrrole-2,3'-oxindoles] were readily accessed by oxidative dehydrogenation. Notably, the inversion of the diastereoselectivity of the spiro[pyrrolidine-oxindole] product could be easily achieved through a facile oxidation-reduction process.