Acid Activation and Chemical Oxidation in the Synthesis of meso‐Tetraphenylporphyrin using a Mixed‐Solvent System

Abstract

The specific roles of solvents in the synthesis of meso-tetraphenylporphyrin (TPP) using a classical mixedsolvent of acetic acid, propionic acid, and nitrobenzene are unclear to date. In this work, we explored the acid-activation process between benzaldehyde and pyrrole using DFT calculations. The catalytic role of carboxylic acids was proven by the formation of a carbocation intermediate. Moreover, the oxidation behavior of nitrobenzene or its analogs was studied by UV/Vis spectroscopy. In particular, the formation of the corresponding amides derived from the reduction of nitrobenzene and its analogs directly confirmed their oxidation behaviors. Specifically, yields of up to 38% of TPP can be obtained from nominally pure to quite pure using the mixedsolvent method with meta-nitrotoluene as the oxidant.[a] Dr.

An Efficient and Robust Method for Selective Conversion of Aniline to Azobenzene Using nano‐TiO2‐P25‐SO3H, under Visible Light Irradiation

“…Nitrobenzene is an indispensable raw material, which can highly be employed in producing a variety of chemical products. More specifically, compelling reasons for selecting nitrobenzene as the oxidant in this novel route for the synthesis of azobenzene are pointed out in the following (53–73):…”

Main Strategies for the Synthesis of meso-Arylporphyrins

“…It was found that the acidity (p K a ) of the medium and the nature of acid catalyst (organic acid, Lewis acid) are crucial for the efficient cyclotetramerization of pyrrole with aldehyde [ 102 ]. In order to reveal the specific role of acid catalysis in combination with chemical oxidation of intermediate products, Sun et al [ 103 ] found that the most effective acid activation of the starting compounds is achieved in a mixture of propionic and acetic acids using nitrobenzene or its derivatives to oxidize intermediate porphyrinogen [ 104 – 106 ]. Highly pure meso -tetraphenylporphyrin was thus obtained in 38% yield in the presence of m -nitrotoluene [ 103 ].…”

“…In order to reveal the specific role of acid catalysis in combination with chemical oxidation of intermediate products, Sun et al [ 103 ] found that the most effective acid activation of the starting compounds is achieved in a mixture of propionic and acetic acids using nitrobenzene or its derivatives to oxidize intermediate porphyrinogen [ 104 – 106 ]. Highly pure meso -tetraphenylporphyrin was thus obtained in 38% yield in the presence of m -nitrotoluene [ 103 ]. Furthermore, other nitrobenzene derivatives proved to be good oxidants providing more than 30% yield of tetraarylporphyrins containing no chlorin impurity [ 103 ] (Table 1 ).…”

“…Highly pure meso -tetraphenylporphyrin was thus obtained in 38% yield in the presence of m -nitrotoluene [ 103 ]. Furthermore, other nitrobenzene derivatives proved to be good oxidants providing more than 30% yield of tetraarylporphyrins containing no chlorin impurity [ 103 ] (Table 1 ).…”

Green Mechanochemistry: Synthesis of Highly Efficient Meso-Substituted Tetra Phenyl Porphyrin Sensitizers for Emerging Organic Photovoltaics Technology

“…Under the inert atmosphere of nitrogen gas, they achieved the final TPP product with a yield of up to ~38% from the nominally pure to fairly pure form. The mixed solvent used for this was m-nitrotoulene, DMSO, and nitrobenzene as oxidants along with the acid catalyst 12,13 . Diane F. Marsh & et al, extended this study and prepared metalloporphyrins, e.g.…”