Theoretical guidance and feedback on the design, preparation, and efficient catalytic oxidation of novel imidazole-modified iron porphyrin catalysts

Abstract

This study develops a new efficient synthesis method for 5-bromo-1,3-difluoro-2-nitrobenzene. Using 4-bromo-2,6-difluoroaniline as a raw material, the process employs a novel imidazole-modified iron porphyrin catalyst, tert-butylhydrogen peroxide as an oxidant, and dichloromethane as a solvent, yielding approximately 70% product after 24 hours at room temperature. The catalyst design was inspired by the imidazole group of a bifunctional small molecule (DFSM) in promoting the formation of the P450 enzyme's Fe^IV+˙O intermediate. This insight led to the creation of imidazole-modified iron porphyrin catalysts with varying side-chain carbon chain lengths. Theoretical calculations demonstrated that a 2-carbon chain length catalyst effectively extracts hydrogen atoms from the oxidant, enhancing Fe^IV+˙O formation and boosting catalytic efficiency. Consequently, two types of side-chain imidazole-modified catalysts, FeC_nIPP (–CH₃, n = 2–6) and FeTAC₂IPP (–NH₂), were synthesized by modifying tetra-p-methylphenylporphyrin iron (FeTMPP) and tetra-p-aminophenyl porphyrin iron (FeTAPP) structures. Experimental results showed that FeC₂IPP and FeTAC₂IPP achieved product yields 3.31-fold and 1.58-fold higher than those of the unmodified catalysts. To enhance the stability of the iron porphyrins, a graphene-oxide-immobilized catalyst (GO-FeTAC₂IPP) was developed. This catalyst is recyclable up to five times while maintaining over 90% of its initial yield. This study provides a novel method for the efficient synthesis of nitro compounds, enabling the conversion of various amino substrates into nitro compounds. The findings offer a new technical pathway for related fields with promising applications.