Selenium compounds play an important role in redox homeostasis in living organisms. One of their major functions is to suppress the harmful effects of hydrogen peroxide, hydroperoxides and downstream reactive oxygen species that lead to oxidative stress, which has in turn been implicated in many diseases and degenerative conditions. The glutathione peroxidase (GPx) family of selenoenzymes plays a key protective role by catalyzing the reduction of peroxides with glutathione. Considerable effort has been expended toward the discovery of small-molecule selenium compounds that mimic GPx. To date, ebselen has been the most widely studied such compound, including in several clinical trials. However, despite its proven lack of significant toxicity, it displays only moderate catalytic activity and very poor aqueous solubility. The cyclic seleninate esters and spirodioxyselenuranes have recently been investigated as potential next generation GPx mimetics, along with structurally related selenenate esters, diazaselenuranes and pincer selenuranes. Their catalytic activities, redox mechanisms and structure-activity relationships are described in this Review, along with a description and discussion of the relative merits of assays for measuring their activities.

1,8-Naphthalene peri-dichalcogenides undergo protonation by Bronsted acids to produce electrophilic cations. Single electron transfer (SET) from the remaining unprotonated electron-rich peri-dichalcogenide to the cation then generates a radical cation and a radical. Thus, the formation of radical species results in severe peak broadening and coalescence of NMR signals when trifluoroacetic acid or other strong acids are added to the peri-dichalcogenide, and the process can be reversed by treatment with base. Further evidence for the formation of radicals stems from EPR, radical quencing with sodium dithionite, and computational experiments. The electron transfer is enhanced by the presence of 2,7-dialkoxy substituents that further increase the electron-donating ability of the dichalcogenides. This is an unusual example of a proton-coupled electron transfer process where an electron-rich molecule reacts with its own conjugate acid via a single electron transfer process.

A six‐step, stereoselective synthesis of cyclin‐dependent kinase 2 (CDK2) inhibitor GNE‐140 was developed. The key bonds were assembled through palladium‐catalyzed Negishi cross‐coupling and Buchwald–Hartwig C−N coupling steps. The stereodiad was established through a single‐step, CuH‐catalyzed enone reduction proceeding in >99 : 1 er and 89 : 11 dr. GNE‐140 was obtained in 25 % overall yield with 98.6 A% HPLC purity.

Several 2,7-dialkoxy-substituted naphthalene-1,8- peri- diselenides were prepared and tested for catalytic antioxidant activity in an NMR-based assay employing the reduction of hydrogen peroxide with stoichiometric amounts of benzyl thiol. Acidic conditions enhanced their catalytic activity, whereas basic conditions suppressed it. The highest activity was observed with a 2,7-bis(triethyleneglycol) derivative. These compounds serve as mimetics of the antioxidant selenoenzyme glutathione peroxidase. Studies based on NMR peak-broadening effects and EPR spectroscopy indicated that a thiol-dependent SET reaction occurs under the conditions of the assay, which can be reversed by the addition of triethylamine. In contrast, peak broadening induced by proton-catalyzed electron transfer during the treatment of naphthalene-1,8- peri -diselenides with trifluoroacetic acid can be suppressed by the addition of excess thiol. These observations provide new insights into the redox mechanisms of these processes.

A synthetic methodology for a protecting-group-free formation of 3-aryl-substituted 4-aminopyrazoles from acetophenones via a telescoped oximation and hydrazine condensation of 1,3-ketoaldehydes to generate nitrosopyrazoles, and copper-catalyzed NaBH4 reduction of the nitroso group, was demonstrated. The synthesis tolerates a broad scope of substrates with a variety of substituents on the phenyl ring to afford the desired products.