Construction of C(sp2)-X (X = Br, Cl) Bonds through a Copper-Catalyzed Atom-Transfer Radical Process: Application for the 1,4-Difunctionalization of Isoquinolinium Salts.

A highly efficient Cu-catalyzed 1,4-difunctionalization of isoquinolinium salts was developed with ether and X- (X = Br, Cl) as the halogen source under mild conditions. This transformation involves the combination of oxidative coupling and copper-catalyzed halogen atom-transfer radical processes. This method not only provides an efficient way to prepare various substituted azaarenes but also achieves the selective construction of C(sp2)-X (X = Br, Cl) bonds from a halogen anion and nucleophilic carbon atom via a free-radical process.