Asymmetric Proline-Catalyzed Addition of Aldehydes to 3H-Indol-3-ones: Enantioselective Synthesis of 2,3-Dihydro-1H-indol-3-ones with Quaternary Stereogenic Centers

The proline-catalyzed addition of various aliphatic aldehydes to sterically hindered 2-aryl-substituted 3H-indol-3-ones affords 2,2-disubstituted 2,3-dihydro-1H-indol-3-one derivatives with excellent enantioselectivities. In addition, the synthesis of a chiral derivative, (S)-2-(2-bromophenyl)-2,3-dihydro-2-(2-hydroxyethyl)-1H-indol-3-one, which can be used as an intermediate for the preparation of the natural product hinckdentine A was accomplished with a high level of enantioselectivity.