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(α) and C(β) 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 β-nitro oxindole into the corresponding β-amino derivative discloses synthetically useful transformations, exploitable to generate pharmaceutically attractive molecular targets.