Fluoroalkylation of Porphyrins: Generation of 2- and 20Perfluoroalkyl-5,10,15-triarylporphyrin Radicals and their Intramolecular Cyclizations

Treatment of 5,10,15-triarylporphyrin (1) with perfluoroalkyl iodides (RfI,2) in the presence of Na2S2O4/NaHCO3 in DMSO-CH2Cl2 at 65 °C for 3 hours gave a mixture of 2-polyfluoroalkyl-5,10,15-triarylporphyrins 3 and 5,10,15-triaryl-20-polyfluoroalkylporphyrins 4. When 1,3diiodohexafluoropropane (2e) was reacted under the same conditions for 8 hours, the products were 5,10,15-triaryl-2,20(hexafluoropropanediyl)porphyrins 5. Both 3e and 4e afforded the same compounds 5 at 65 °C after a reaction time of 6 hours. Either 2-(2chlorotetrafluoroethyl)-5,10,15-triphenylporphinato zinc(II) (Zn3aa) or 5,10,15-triphenyl-20-(2-chlorotetrafluoroethyl)porphinato zinc(II) (Zn4aa) resulted in 5,10,15-triaryl-2,20-(tetrafluoroethanediyl)porphinato zinc(II) (Zn7) in excess Na2S2O4/NaHCO3 in DMSO-CH2Cl2 at 100 °C after 3 hours. Both Zn5a and Zn7 can be hydrolyzed quantitatively to 5,10,15triaryl-2,20-(20’-oxo)(tetrafluoropropanediyl)porphinato zinc(II) (Zn8) and 5,10,15-triphenyl-2,20-(20’-oxo)(difluoroethanediyl)porphinato zinc(II) (Zn9), respectively in the presence of silica gel at room temperature.