Asymmetric hydrogenation of 2-substituted N-protected-indoles catalyzed by rhodium complexes of BINOL-derived phosphoramidites

The rhodium-catalyzed asymmetric hydrogenation of 2-substituted N-protected-indoles using monodentate phosphoramidites as ligands was examined. Full conversion and 74% ee, were obtained with a catalyst based on PipPhos. The use of a catalytic amount of base is necessary for activity; best results were obtained with Cs2CO3.

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Methyl (S)-1-acetyl-2,3-dihydro-1H-indole-2-carboxylateC12H13NO3Ee 74%[α]D = −43.8 (c 1.03, CHCl3)Absolute configuration: (S)Source of chirality: catalytic asymmetric hydrogenation