kinetic resolution of 2-substituted indoline derivatives was achieved by hydrogentransfer to imines by means of a chiral phosphoric acid catalyst. The oxidative kinetic resolution was applicable to racemic alkyl- or aryl-substituted indolines, and the remaining indolines were obtained in good yields with excellent enantioselectivities.
We have developed a highly efficient and practical strategy for the kinetic resolution of indoline derivatives, involving a chiral Brønstedacid-catalyzed iminium ion formation and asymmetric transfer hydrogenation cascade process. The kinetic resolution allows the synthesis of 2-substituted N-benzylindolines in good yields with moderate to excellent enantioselectivities.