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The review aims at being an exhaustive summary of the use of Huisgen azide-alkyne dipolar addition in the synthesis of tetrapyrrolic compounds, mainly porphyrins, phthalocyanines, chlorins and bacteriochlorins.

This work describes the synthesis of ruthenium(IV) $\mu$-oxo porphyrin complexes of general formula [Ru^IV(TPP)(X)]₂O which have been applied as catalysts in nitrene transfer reactions using aryl azides (ArN${}_3)$ as nitrene sources. Collected data indicated that the catalytic efficiency of [Ru^IV(TPP)(OCH${}_3)$]₂O was comparable to that of Ru^II(TPP)CO because of their analogous reactivity towards aryl azides to give the same catalytically active bis-imido species Ru^VI(TPP)(ArN)₂. The reaction of [Ru^IV(TPP)(OCH${}_3)$]₂O with Ph₃CN₃ or (CH${}_3{)}_3$SiN₃ afforded [Ru^IV(TPP)(N${}_3)$]₂O which was fully characterised, its molecular structure was also determined by single crystal X-ray analysis.

Click chemistry has become a very popular and efficient concept for synthetic chemists for the construction of new molecules. Among the click chemistry approaches known to date, it is undoubted that the copper-catalyzed alkyne-azide 1,3-dipolar cycloaddition (CuAAC) has played a key role. Such reactions in general offer virtually unlimited possibilities to prepare new molecules for $e.g$. materials science applications. As such, the synthesis of porphyrin–fullerene conjugates obtained via CuAAC are summarized within the present review article.

This work describes the aziridination process of $\alpha$-methylstyrene by using electron poor aromatic azides in the presence of metal-based porphyrins as catalysts. Different ruthenium and cobalt-based porphyrins were successfully employed for the synthesis of $N$-aryl aziridines performed under a traditional batch methodology and under continuous flow conditions. In general, yields obtained using ruthenium-based catalysts in a traditional batch process were higher than those observed when the reaction was performed under flow conditions. However, cobalt-based porphyrins showed better activities and short reaction times when employed in a flow system process. DFT calculations were also performed in order to understand the influence of substituents on the porphyrin ring in the aziridination process.

Man has always used his environment to heal himself. Until 1869 all medicines came mainly from plants (e.g. opium for pain relief, Figure 8.46, Section 8.8.1) or animals (e.g. badger skin and meat to relieve snake or scorpion bites). In 2010, there were 1000 active ingredients in drugs sold in pharmacies, of which 10% were unmodified natural products, 29% were derivatives of natural products (hemisynthesis) and 61% were synthetic products. Using bio-informatics and artificial intelligence methods, an estimated 166 billion different molecules can be prepared by combining 17 atoms comprising C, N, O, S, F, Cl, Br and I, and by applying known synthesis methods and standard stability criteria. By applying medicinal chemistry criteria (structure/biological activity relationships) to this molecular space called GBD17, it is estimated that 10 million of these molecules could become drugs…

The bioconversion of xenobiotics often involves oxidation-reduction reactions and one representative example is the reductive decolorization of azo dyes. The bioreduction of an azo dye as model xenobiotic by a mixed microbial culture (activated sludge) was thus chosen as a model system in the present study. The aim was to investigate the effect of a respiratory inhibitor, namely sodium azide (a cytochrome oxidase inhibitor) on this bioconversion, when carried out by two different activated sludge mixed culture inocula. Different biomass conditioning pretreatments were also studied, i.e., using a mixed culture freshly harvested from the growth bioreactor or after aerobic incubation in the absence of carbon source (starved). The azide inhibition effect was observed to lessen with the increase in starvation time for both mixed cultures. This result points to the existence of an alternative dye bioconversion mechanism, triggered in the starved biomass, in which the involved pathways are not inhibited by azide. For one of the inocula, this alternative mechanism was found to be dependent on the availability of glucose in the bioconversion medium.

Cyanide and azide, powerful poisons that block respiration, are constantly released in the environment because of their extensive industrial use. In this research the effect of millimolar concentrations of cyanide and azide on Salmonella. typhimurium growth and on its membrane proteins, using cytochromes as a probe, was investigated. S. typhimurium was more resistant to azide than to cyanide; the yield after 24 h growth was 74% of the control in 5 mM azide compared to 28% in 5 mM cyanide, and 24% of the control in 10 mM azide compared to 0% in 10 mM cyanide. When cyanide was added to a suspension of oxidized S. typhimurium cells, a cytochrome d-CN complex was formed, detectable by difference spectrophotometry, but no complex was detectable when azide replaced cyanide. When both compounds were added to the cells, azide competitively inhibited the cytochrome d-CN complex formation, illustrating the binding of azide to cytochrome d as well. Secondary and Dixon plots were parabolic, suggesting that two azide molecules bound to cytochrome d. Data also showed that cyanide had more affinity than azide for cytochrome d in S. typhimurium.