A new system for the high regio- and stereoselective aminohalogenation of cinnamic esters with NBS and p-toluenesulfonamide (TsNH₂) as bromine/nitrogen sources catalyzed by Al powder in CH₂Cl₂ has been developed. This method offered vicinal haloamine products in high yield (up to 97%) at room temperature without inert gases protection. The cinnamic esters bearing a strong electron-donating group (e.g., OCH₃) on the 4-position of the benzene ring afforded the trans isomer as the sole products of α-bromine and β-amine adductive products up to nearly quantitative yields. However, the cinnamic esters without the strong electron-donating group (e.g., OCH₃) or bearing a poor electron-withdrawing group (Br) on the 4-position of the benzene ring, the yield of reaction was decreased and the α-amine and β-bromine adductive products as sole product were afforded. These results of experiment indicated that the aminohalogenation to cinnamic esters catalyzed by Al-powder is an electrophilic addition reaction. In this paper, a series of the aminohalogenation of cinnamic esters (20 samples) has been investigated. All products structure were characterized by elemental analysis, ¹H NMR and ¹³C NMR and the possible reaction pathway have been proposed.

Key words: aminobromination, Al powder, cinnamic ester derivatives, regioselective, stereoselective