N-Aryl indole-derived C-N bond axially chiral phosphine ligands: synthesis and application in palladium-catalyzed asymmetric allylic alkylation

N-Aryl indole-derived C-N bond axially chiral phosphine ligands 2a-c were obtained by DDQ oxidation of N-aryl indoline-derived phosphine oxide followed by silane reduction. Resolution of C-N bond atropisomers was achieved by chiral HPLC. The investigation of the rotation barrier for the C-N bond axial stability of phosphines and the determination of the absolute configuration of 2c are described. Finally, the ability of the chiral ligand 2c was demonstrated in a palladium-catalyzed asymmetric allylic alkylation (up to 99% ee). (C) 2010 Elsevier Ltd. All rights reserved.