A Visible Light and Iron-mediated Carbocationic Route to Polysubstituted 1-Halonaphthalenes by Benzannulation using Allylbenzenes and Polyhalomethanes
A wide array of polysubstituted 1-bromo and chloronaphthalenes are obtained from coupling of allylbenzenes and polyhalomethanes. The reaction is mediated by iron metal under visible light irradiation and proceeds via a Kharasch addition intermediate followed by intramolecular FeIII mediated Friedel-Crafts alkylation, with the formation of two Csp2?Csp2 bonds in the process. This method gives easy access to 1-halonaphthalenes with substituent(s) at C-5 to C-8 that are otherwise hard to synthesize. (Figure presented.).