An Improved Method for the Bromination of Metalated Haloarenes via Lithium, Zinc Transmetalation: A Convenient Synthesis of 1,2-Dibromoarenes.

A facile protocol for the synthesis of 1,2-dibromoarenes is described. A standard ortho-lithiation/bromination procedure, when applied to bromoarenes, resulted in poor yields of the corresponding 1,2-dibromoarenes (13-62% yield). However, transmetalation of the transient aryllithium intermediate to an arylzinc species with ZnCl2, followed by bromination, resulted in dramatically improved yields of the synthetically useful 1,2-dibromoarenes (68-95% yield).