In contrast to the CuCl/CuCl2-system introduced before we were interested in the influence of the copper species used on the reaction control and the resulting conversion. Several experiments were compared using all possible combinations of CuCl, CuBr, CuCl2, and CuBr2. All experiments were carried out for 21 h. The new reaction conditions are summed up in Table (entry 6-9) and the corresponding SEC traces are shown in Figure .