Efficiency enhanced greener approach for bromination of activated aromatic compounds

Abstract

the generated organobromides can be used as building blocks in a variety of syntheses due to their versatility. The use of the toxic and highly reactive molecular bromine (Br2) makes these brominations difficult and dangerous. Other synthesis processes involve toxic modified brominating reagents like N-bromosuccinimide (NBS) or expensive bromine carrying agents. Most of them are still hazardous due to liberated bromine. A new in-situ bromination of activated aromatic compounds which is quick, cheap, safe, effective and greener method was studied by using solid KBrO3 and aqueous NaBr in glacial acetic acid in 45 minutes at room temperature. Vanillin, 2- Nitroaniline, 4-Niroaniline, 4-Aminobenzoic acid (A1-A4) were subjected to the bromination in triplicates and higher average yield of brominated products 78.67%, 89.79%, 88.68% and 73.24% obtained respectively. Furthermore, this insitu bromination process was enhanced by adding 10%(w/w) amount of silica gel and increased average yields obtained for 5- Bromo-4-hydroxy-3-methoxy-benzaldehyde (88.02%), 4-Bromo-2- nitroaniline (93.45%), 2-Bromo-4-nitroaniline (93.14%) and 2-Bromo-4- aminobenzoic acid (85.21%) at the same reaction conditions.