FeSO4· 7H2O was proven to work as effective promoter for the direct arylation of benzoquinones with aryl boronic acids in the presence of K2S2O8. In the arylation, slow addition of iron solution was crucial to efficiently proceed with the reaction. Interestingly, the Fe-mediated arylation could be converted into a catalytic reaction by using hydroquinones, instead of benzoquinones, or addition of ascorbic acid.
