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

Abstract

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 reports 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 environmentally friendly. RESULTS Compared with the traditional synthesis, tetrabromoethylcyclohexane is obtained with equivalent yield (90%), at room temperature, in a short reaction time (∼2 h compared with the previous 17 h) and with a strong reduction of the use of organic solvents; finally two isomers are obtained instead of four. 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 syntheses 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 bonds in water were confirmed with the synthesis of tetrabromoethylcyclohexane. Given the wide use of brominated compounds in the chemical industry, this procedure could be of wide interest. © 2015 Society of Chemical Industry