Bromination of Ketones by Palladium(II). An Asymmetric α-Bromoketones Catalytically Synthesized by a Mono Palladium(II) Catalyst

The oxidation of ketones by monometallic [Pd(CH3CN)2(S)-Tol-BINAP](BF4)2 A or [Pd(CH3CN)2(S)-METBOX](BF4)2 B in aqueous THF containing copper(II) bromide produced chiral α-bromoketones. The α-bromoketone products were obtained with moderate to high enantiomeric excess (68-89% ee) and good isolated yields (70-90%). The highest optical purities were 89% ee for cycloheptanone. Catalyst B gave slightly higher enantioselectivities than catalyst A. All symmetric ketones gives only one product whereas, oxidation of 2-butanone gives the 3-bromo-2-butanone and 1-bromo-2-butanone. The α-bromoketone products were characterized by FTIR, 1H, 13C-NMR and GC/MS.