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.
- cross-dehydrogenative coupling
- fluorinated solvents
- iron catalysis
- oxidative cross-coupling