Trapping of Oxonium Ylide with Isatins:  Efficient and Stereoselective Construction of Adjacent Quaternary Carbon Centers

The 3-substituted 3-hydroxyindolin-2-ones with adjacent quaternary stereocenters were constructed in a single step via an efficient and stereoselective trapping of oxonium ylide with isatins. This reaction proceeds well in supercritical CO₂ and is an example of the ability to use green approaches to efficiently construct polyfunctional molecules.