“…With AIBN as the best radical promoter, a variety of solvents such as chlorobenzene, ethanol, toluene, and p -xylene were further screened, and no reaction took place in these solvent systems (Table S1, entries 4–8). When CF 3 CO 2 H was employed as solvent, only 2,2′-dithiodianilinium trifluoroacetate was obtained in moderate yield (Table , entry 6, see the Supporting Information (SI) for its crystal structure). Further optimization was carried out with the use of various amounts of AIBN (Table , entries 1 and 7–9), and we were glad to find that increasing the amount of AIBN from 5 to 20 mol % almost doubled the yield of 3a (84% based on 1a ); however, the yield of 3a is not further increased when the amount of AIBN is over 20 mol %.…”