High Regioselective Aminobromination of β-Nitrostyrene Derivatives with 1,3-Dibromo-5,5-dimethyl Hydantoin

A new protocol for the high regioselective aminobromination of beta-nitrostyrene derivatives with 1,3-dibromo-5,5-dimethyl hydantoin(DBDMH) as nitrogen/bromine sources was developed. Two kinds of beta-nitrostyrene derivatives got different reaction results under different reaction conditions. For the beta-nitrostyrene derivatives, this protocol offered vicinal haloamine products in good to excellent yields(up to 97%) at room temperature in CH3CN catalyzed by Na2CO3. For the beta-methyl-beta-nitrostyrene, the good to excellent yields(up to 95%) were also achieved refluxed in CH3CN catalyzed by KOH. The strong electron-donating substituents (e.g., CH3O) on the 4-position of benzene ring could deactivated the reaction activity of beta-nitrostyrenederivetives with DBDMH. However, the vicinal haloamines were also afforded as the sole addition product. Whereas strong electron-withdrawing substituent(e.g., NO2) could activated reaction activity remarkably and the vicinal haloamines were afforded as the sole addition product, too. The result revealed that the addition reaction has a nucleophilic addition feature. The aminobromination of 20 examples of beta-nitrostyrenes were investigated in this work and the structure of all products were confirmed by the corresponding H-1 NMR, C-13 NMR spectra and HRMS (ESI). A possible mechanism involving a nucleophilic conjugate addition was proposed.