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).