Iron and Copper Salts in the Synthesis of Benzo[b]furans

Intramolecular C-O bond forming reactions of aryl 2-bromobenzyl ketones lead to benzo[b]furans. The cyclizations can be catalyzed by 10 mol% of iron trichloride (of 98% or of 99.995% purity) or sub-mol% quantities of copper(II) chloride (of 99.995% purity).