科研之友
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摘要
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 a-bromine and beta-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 alpha-amine and beta-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, H-1 NMR and C-13 NMR and the possible reaction pathway have been proposed.
- 出版日期2011-5-14
- 单位陕西师范大学
