Asymmetric [1,2] Stevens rearrangement of (S)-N-benzylic proline-derived ammonium salts under biphasic conditions

The Stevens rearrangement of (S)-N-benzylic proline-derived ammonium salt with cesium hydroxide in 1,2-dichloroethane is shown to proceed with a high degree of the N-to-C chirality transmission to afford the alpha-substituted proline derivatives in high enantio-purities.