Abstract
Iron(III) fluorinated porphyrins play a central role in the biomimetics of heme enzymes and enable cleaner routes to the oxidation of organic compounds. The present work reports significant improvements in the eco-compatibility of the synthesis of 5,10,15,20-tetrakis-pentafluorophenylporphyrin (H2TPFPP) and the corresponding iron complex [Fe(TPFPP)Cl], and the use of [Fe(TPFPP)Cl] as an oxidation catalyst in green conditions. The preparations of H2TPFPP and [Fe(TPFPP)Cl] typically use toxic solvents and can be made significantly greener and simpler using microwave heating and optimization of the reaction conditions. In the optimized procedure it was possible to eliminate nitrobenzene from the porphyrin synthesis and replace DMF by acetonitrile in the metalation reaction, concomitant with a significant reduction of reaction time and simplification of the purification procedure. The Fe(III)porphyrin is then tested as catalyst in the selective oxidation of aromatics at room temperature using a green oxidant (hydrogen peroxide) and green solvent (ethanol). Efficient epoxidation of indene and selective oxidation of 3,5-dimethylphenol and naphthalene to the corresponding quinones is observed.
Highlights
A study of microwave synthesis was performed in order to achieve a faster and greener route
The optimization of the procedure started from previous reports of metaloporphyrin synthesis [23,30] and involved a systematic evaluation of the reaction conditions
The syntheses of H2 TPFPP and [Fe(TPFPP)Cl] have been optimized using microwave methods to allow the production of these important fluorinated porphyrins in a more eco-sustainable manner, and the use of the prepared [Fe(TPFPP)Cl] has been investigated in green catalytic oxidation reactions
Summary
Fluorinated porphyrins have been attracting considerable attention as components of photonic materials and in biological applications, such as imaging or photodynamic therapy, owing to their versatile photophysics, electron withdrawing properties and resistance to oxidative degradation [1,2,3,4,5]. Green procedures for halogenated were porphyrins synthesis by andlong reaction times, the use of high temperatures and harmful or corrosive solvents. Their metalation using Fe have not been described. With theusing aim ofFe demonstrating a more eco-compatible process from catalyst synthesis toofoxidative their metalation have not been described Such methods are potentially significant catalysis, the environmentally present work reports the optimization of the synthesis and metalation. With the aim of demonstrating a more eco-compatible process from catalyst synthesis to oxidative catalysis, the present work reports the optimization of the synthesis and metalation of H2 TPFPP using microwave heating.
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