Organocatalytic Conjugate Addition of Nitroalkanes to 3-Ylidene Oxindoles: A Stereocontrolled Diversity Oriented Route to Oxindole Derivatives

An efficient and highly enantioselective Michael addition of nitroalkanes to 3-ylidene oxindoles is described, mediated by thiourea-based bifunctional organocatalysts. The stereochemistry at C-alpha and C-beta centers is perfectly controlled, and the intermediate C-3 enolate is trapped with a second Michael acceptor. The developed one-pot three-component consecutive reactions generate up to four contiguous stereocenters, including the C-3 all-carbon quaternary center, in a perfectly defined configuration. The conversion of the beta-nitro oxindole into the corresponding beta-amino derivative discloses synthetically useful transformations, exploitable to generate pharmaceutically attractive molecular targets.