Biocatalytic oligomerization of azoles; experimental and computational studies

Azoles are an important class of small molecules in pharmaceuticals and in pesticides which are found in surface water and effluents of wastewater treatment plants. With increasing research on novel characteristics of such compounds, they are considered emerging contaminants, thus, the efficiency of existing technologies for their treatment becomes an important matter. Peroxidases have proven to be effective in transformation of phenols and anilines via radical coupling. Here, the feasibility of oxidative polymerization of selected azoles with soybean peroxidase is demonstrated. The sensitivity of such treatment to the most important parameters, pH, enzyme activity and peroxide concentration, was investigated. Enzymatic treatment was shown to be effective with >= 70% transformation efficiency in all cases, with hydroxybenzotriazole having the highest efficiency among the substrates tested, thus providing a baseline for future study of real wastewater and environmental samples. Radical-coupling products after treatment were shown by mass spectrometry to be dimers and trimers and structures are proposed based on regiochemistry predicted from radical spin-density computations. Ionization energy and reduction potential of the compounds studied were also computed to look for a correlation with enzyme reactivity.

Automated summary

Azoles are important small molecules found in pharmaceuticals and pesticides that are now considered emerging contaminants. Peroxidases have been shown to effectively transform these compounds, with enzymatic treatment achieving a transformation efficiency of >= 70% in all cases. Mass spectrometry analysis revealed the formation of dimers and trimers as radical-coupling products after treatment, with structures proposed based on predicted regiochemistry.