“…To prevent this, ethyl trichloroacetate (ETA) reactivator is often used. Another method of stabilizing the vanadium active center is applying ligands with electron-donating atoms, oxygen or nitrogen [ 14 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]. In our previous works it was found that the vanadium metallocene and post-metallocene catalysts with oxazoline ligand activated by the traditional organoaluminium compound (AlEt 2 Cl) and ETA can be successfully used for COC synthesis [ 35 , 36 , 37 , 38 , 39 , 40 , 41 ].…”