Copper Powder-Catalyzed Regio- and Stereoselective Aminobromination of α,β-Unsaturated Ketones with TsNH₂ and NBS as Nitrogen and Halogen Sources

The regio- and stereoselective aminobromination of α,β-unsaturated ketones catalyzed by copper powder has been established with 4-TsNH2 and NBS as the nitrogen/bromine sources, respectively. This method provides an easy access for preparation of vicinal aminohalo derivatives in the presence of 1 mol % catalyst. Electron-rich α,β-unsaturated ketones afforded the corresponding aminobrominated products in excellent yields (up to 99.8%), revealing that the addition has an electrophilic feature.