A new bromination of methylarenes was developed through boron tribromide under the mild conditions, which is different from traditional free-radical process. The advantage of this method is the good yield and high selectivity. During investigation of electron and steric effect, it was found that substrates with various substitutional groups could give expected products in moderate to good yields. Both steric hindrance and electron effect would affect the reaction. Electron-donating substitute was favorable to bromination, while electron-withdrawing group decreased the yield. At the same time, the influence of solvent, temperature, mass of boron tribromide and reaction time on the bromination was also investigated.

Key words: boron tribromide, bromination, methylarene, bromomethylarene