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 β‐dicarbonyl compounds. The new conditions were utilized in the synthesis of 2′′′‐dehydroxycalodenin B in only four synthetic steps. Not just a solvent: The use of fluorinated solvents leads to a significant rate acceleration and enhancement of the chemoselectivity of the iron‐catalyzed oxidative coupling of phenols. This method was used for the synthesis of 2′′′‐dehydroxycalodenin B.