## 3 Results and Discussion  
The ratio between bromide and chloride concentrations in solution was expected to reflect the prevalent form of the radical deactivator metal complex, as a result of the fast halide exchange processes [22]. A higher concentration of Cu\({}^{(II)}\)Br\(\cdot L\) would potentially be associated with a dominant AERC, whereas an abundance of Cu\({}^{(II)}\)Cl\(\cdot L\) was expected to predominantly favour ATRC. The development of the AERC should, therefore, be based on a cyclization process requiring a minimal starting amount of metal chlorides. The ARGET-ATRC of dichloroamide **1** (Figure 1) [25], that can work with only 0.01 mol of CuCl\({}_{2}\) for each mol of substrate (see Section 2.2), was thus considered a suitable starting point. The inclusion of increasing amounts of NaBr within the reaction mixture was then expected to lead to the formation of increasing amounts of brominated compounds, as depicted in Figure 3.  
The desired product (**3**) may arise from the entrapment of the transient radical **1\({}^{\prime\prime}\)** by Cu\({}^{(II)}\)Br\(\cdot L\)., i.e., through the AERC mechanism. Conversely, the same metal complex may promote the formation of the constitutional isomeric lactam **3a** via a radical substitution at the 3 position of the ATRC product **2**[6]. An analogous substitution mechanism may also apply to the formation of dibromide **3b** from the AERC product **3**. However, the formation of **3a** and **3b** was expected to be less likely due to the low operating temperature (37 \({}^{\circ}\)C) and the higher C-Cl bond dissociation energy (83 kcal/mol), compared to that of the C-Br bond (77 kcal/mol) [27]. When a moderate amount of NaBr (0.25 mol for each mol of **1**) was included into the described ARGET-ATRC reaction mixture, a new product was formed, together with the standard product **2**. This new compound, which exhibited higher retention in GC-MS (r.t. \(\sim\)13.95 min) compared to **2** (GC r.t. \(\sim\)12.90 min), was characterized by a MS pattern compatible with a bromochlorolactam. Further characterization through multinuclear NMR spectroscopy, after careful chromatographic fractionation, confirmed the identity of compound **3**. The limited effectiveness of the radical substitution mechanisms that produce **3a** or **3b** under AERC conditions was then confirmed. This was further confirmed by heating a purified sample of compound **2** at 50 \({}^{\circ}\)C for 24 h in the presence of 10 mol% of the Cu\({}^{(\text{II})}\)Br\({}_{2}\)-TPMA metal complex. Under these conditions, **2** converted to another compound, characterized by a molecular ion very near to that of lactam **3** but showing a different GC retention time (\(\sim\)13.85 min) and mass fragmentation (Figure 4). It was thus assigned to **3a**. As the operativity of the AERC mechanism was demonstrated, further experimentation was directed towards increasing the production of **3**. Therefore, a set of ATRC on **1** were set up, incorporating increased amounts of NaBr. Unfortunately, the GC yield of **3** did not correlate linearly with the amount of added bromide. This unexpected behavior was attributed to the chemical complexity of the system. Indeed, the ARGET-ATRC involves  
Figure 4: MS characterization of **3** and **3a**. Figure 3: Competition between ATRC (ending in blue drawing) and AERC of **1**. Possible further substitution products are also described. a multitude of chemical species, such as Na\({}_{2}\)CO\({}_{3}\), ascorbic acid, and the metal complex, whose mutual interactions and relative solubilities can be altered by the added salts. To simplify the composition of the reaction mixture, a supplemental activator reducing agent (SARA) process was considered. In the SARA radical mechanism, copper compportionation is assumed to dominate over disproportionation [28], making it possible to utilize Cu\({}^{0}\) as both a reducing agent and a metal source for the catalytic complex. This eliminates the need for the addition of the copper salt and the reductant.