Abstract:

A new system for the high regio- and stereoselective aminobromination of olefins with p-toluenesulfonamide(TsNH₂) and 1,3-dibromo-5,5-dimethyl hydantoin(DBDMH) as nitrogen/bromine sources catalyzed by a new catalyst which produced in-situ from Zn powder has been developed. This protocol offered vicinal haloamine products in high yield(up to 99%) at room temperature in CH₂Cl₂. The strong electron-donating group(such as OCH₃) are connected on the 4-position of the benzene ring which attached directly to the carbon-carbon double bond of substrats, the reaction afforded the trans isomers(α-bromo-β-amino) as the sole product up to nearly quantitative yield. However, the strong electron-withdrawing group(NO₂) or the poor electron-withdrawing group(Br and F) are linked on the 4-position of the benzene ring, the reaction afforded the another reversal isomers in regioselective(α-amino-β-bromo) as the sole product, but the slightly low yields were obtained. In this paper, a series of the aminobromination of olefins(20 samples) have been investigated. The result indicates that the method has widely applicability to the aminobromination of olefins. All the product structures were characterized by ¹H NMR, ¹³C NMR and elemental analysis, and the possible reaction pathway was proposed.

Key words: Aminobromination, Olefin, Zn powder, Regioselectivity, Stereoselectivity, Catalysis