Sustainable improvement of the tetrabromoethylcyclohexane synthesis using Amino ILs as Catalysts in Water. A facile and environmentally-friendly procedure

BACKGROUND: Due to environmental concerns, there is a need to eliminate or drastically reduce the use of conventional organic solvents, as these are environmentally harmful. This paper focuses on a novel one-pot synthesis of tetrabromoethylcyclohexane (TBECH) in aqueous medium, using amino-functionalized ionic liquids, which catalyze the reaction and make it more environmental friendly. RESULTS: Compared to the traditional synthesis, tetrabromoethylcyclohexane is obtained with equivalent yield (90%), at room temperature, in short reaction time ( 2h compared to the previous 17h) and with a strong reduction of the use of organic solvents; finally 2 isomers are obtained instead of 4. Furthermore, a novel procedure to prepare the ionic liquids has been designed and two new ones have also been synthesised. The calculated environmental factors (EFs), which measure the environmental sustainability, showed a strong reduction of the use of organic solvents for all the synthesis of ionic liquids and TBECHs. CONCLUSIONS: The excellent properties of amino-functionalized ionic liquids as solvents and catalysts for chemo- and diastereo-selective bromination of C=C bond in water were confirmed with the synthesis of tetrabromoethylcyclohexane. Given the large uses of brominated compounds in chemical industry, this procedure could be specially appreciated.