The mechanistic aspects in hydroxylation reactions catalyzed by fluorinated porphyrins of manganese and iron: Role of aqueous phosphate

The role of aqueous phosphate in the selective hydroxylation of cyclohexane to cyclohexanol (60-68% yields) and cyclohexene to 2-cyclohexene-1-ol (98% yield) has been discussed. Fluorinated porphyrins of manganese and iron were used as catalysts in acetonitrile with aqueous-K₂HPO₄ and t-BuOOH as co-catalyst and oxidant, respectively. The generation of the oxo-manganese reactive intermediate was identified by ¹H, ¹⁹F NMR, EPR, UV-Vis and mass spectral studies. The formation of phosphate adduct of the oxo-manganese reactive intermediates has been proposed on the basis of high binding constant of dipotassium hydrogen phosphate with the catalyst.