Thermo-switchable hydrophobic deep eutectic solvent for CuAAC

Abstract

The use of a deep eutectic solvent with thermo-switchable hydrophobicity properties (lidocaine: decanoic acid) is presented. Upon a gentle thermal trigger, the solvent separated into aqueous and organic layers. This system is well adapted for the CuAAC reaction using an N-heterocyclic carbene copper catalyst. An alkyne–azide cycloaddition of hydrophilic compounds, such as carbohydrates, could be conducted with good yields in the aqueous layer after the thermal separation. The method presented herein causes low contamination of the products by metals and the solvent can be reused at least five times.