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J . Org. Chem. 2019, 84, 4680−4694. DOI:10.1021/acs.joc.8b02269 ◆ Cationic Cu(I) salts generally outperform other Cu(I) or Cu(II) sources in the Chan−Lam arylation of secondary sulfonamides. We attribute the superiority of cationic Cu(I) sources to the absenceof potentially competing X-type ligands (AcO−, Cl−, etc.) that could inhibit coordination of the sulfonamide. ◆ In acetonitrile, 19 still has poor solubility (2.9 mg/mL) when [Cu(ACN)4]PF6 is present; however, upon addition of triethylamine, the mixture clarifies and immediately turns dark green. We attribute this behavior to the oxidation of Cu(I) by air to generate a 2:1 complex between the anion of 19 and a Cu(II) center. ◆ Given the correlation between the Cu loading and amount of dissolved 19, we also assessed the influence of Cu loading on the Chan−Lam reaction itself. While a detailed kinetic study is required to elucidate the reaction mechanism, it is clear that the optimal amount of Cu is 0.5−0.6 equi
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