Significant Enhancement in the Efficiency and Selectivity of Iron-Catalyzed Oxidative Cross-Coupling of Phenols by Fluoroalcohols

Significant enhancement of both the rate and the chemoselectivity of iron-catalyzed oxidative coupling of phenols can be achieved in fluorinated solvents, such as 1,1,1,3,3,3-hexafluoropropan-2-ol (HFIP), 2,2,2-trifluoroethanol (TFE), and 1-phenyl-2,2,2-trifluoroethanol. The generality of this effect was examined for the cross-coupling of phenols with arenes and polycyclic aromatic hydrocarbons (PAHs) and of phenol with b-dicarbonyl compounds. The new conditions were utilized in the synthesis of 2'''-dehydroxycalodenin B in only four synthetic steps.