Synthesis and Optical Resolution of Aminophosphines with Axially Chiral C(aryl)−N(amine) Bonds for Use as Ligands in Asymmetric Catalysis
2006-09-15T00:00:00Z (GMT) by
N-Aryl indoline-type aminophosphines 1a−c were obtained in good yields by a nucleophilic aromatic substitution (SNAr) reaction followed by silane reduction. Aminophosphine 1d was also prepared from 2,3-difluorobenzaldehyde (4) via dimethylhydrazone. Optical resolution of C(aryl)−N(amine) bond atropisomers was achieved using (S)-(+)-di-μ-chlorobis[2-[(dimethylamino)ethyl]phenyl-C2,N]dipalladium(II) ((S)-10). The determination of absolute configuration and the investigation of the rotation barrier for C(aryl)−N(amine) bond axial stability of an aminophosphine 1 are described. Finally, the ability of the chiral phosphine ligand 1 is demonstrated in a catalytic asymmetric reaction, such as a palladium-catalyzed asymmetric allylic alkylation of 1,3-diphenyl-2-propenyl acetate with dimethyl malonate (up to 95% ee).