Chalcogen-bonding interactions have recently gained considerable attention in the field of synthetic chemistry, structure, and bonding. Here, three organo-spiroselenuranes, having a Se(IV) center with a strong intramolecular Se•••N chalcogen-bonded interaction, have been isolated by the oxidation of the respective bis(2-benzamide) selenides derived from an 8aminoquinoline ligand. Further, the synthesized spiroselenuranes, when assayed for their antioxidant activity, show disproportionation of hydrogen peroxide into H 2 O and O 2 with first-order kinetics with respect to H 2 O 2 for the first time by any organoselenium molecules as monitored by 1 H NMR spectroscopy. Electron-donating 5-methylthio-benzamide ring-substituted spiroselenurane disproportionates hydrogen peroxide at a high rate of 15.6 ± 0.4 × 10 3 μM min −1 with a rate constant of 8.57 ± 0.50 × 10 −3 s −1 , whereas 5-methoxy and unsubstituted-benzamide spiroselenuranes catalyzed the disproportionation of H 2 O 2 at rates of 7.9 ± 0.3 × 10 3 and 2.9 ± 0.3 × 10 3 μM min −1 with rate constants of 1.16 ± 0.02 × 10 −3 and 0.325 ± 0.025 × 10 −3 s −1 , respectively. The evolved oxygen gas from the spiroselenurane-catalyzed disproportion of H 2 O 2 has also been confirmed by a gas chromatograph−thermal conductivity detector (GCTCD) and a portable digital polarographic dissolved O 2 probe. Additionally, the synthesized spiroselenuranes exhibit thiol peroxidase antioxidant activities for the reduction of H 2 O 2 by a benzenethiol co-reductant monitored by UV−visible spectroscopy. Next, the Se•••N bonded spiroselenuranes have been explored as catalysts in synthetic oxidation iodolactonization and bromination of arenes. The synthesized spiroselenurane has activated I 2 toward the iodolactonization of alkenoic acids under base-free conditions. Similarly, efficient chemo-and regioselective monobromination of various arenes with NBS catalyzed by chalcogen-bonded synthesized spiroselenuranes has been achieved. Mechanistic insight into the spiroselenuranes in oxidation reactions has been gained by 77 Se NMR, mass spectrometry, UV−visible spectroscopy, singlecrystal X-ray structure, and theoretical (DFT, NBO, and AIM) studies. It seems that the highly electrophilic nature of the selenium center is attributed to the presence of an intramolecular Se•••N interaction and a vacant coordination site in spiroselenuranes is crucial for the activation of H 2 O 2 , I 2 , and NBS. The reaction of H 2 O 2 , I 2 , and NBS with tetravalent spiroselenurane would lead to an octahedral-Se(VI) intermediate, which is reduced back to Se(IV) due to thermodynamic instability of selenium in its highest oxidation state and the presence of a strong intramolecular N-donor atom.

A copper catalyzed efficient synthetic method has been developed to access bis(N-arylbenzamide) selenides from 2-halo-N-arylbenzamide substrates and disodium selenide in HMPA at 110 °C.

SARS-CoV-2 main protease (M pro /3CL pro ) is a crucial target for therapeutics, which is responsible for viral polyprotein cleavage and plays a vital role in virus replication and survival. Recent studies suggest that 2-phenylbenzisoselenazol-3(2H)-one (ebselen) is a potent covalent inhibitor of M pro , which affects its enzymatic activity and virus survival. Herein, we synthesized various ebselen derivatives to understand the mechanism of M pro inhibition by ebselen. Using ebselen derivatives, we characterized the detailed interaction mechanism with M pro . We discovered that modification of the parent ebselen inhibitor with an electron-withdrawing group (NO 2 ) increases the inhibition efficacy by 2-fold. We also solved the structure of an M pro complex with an ebselen derivative showing the mechanism of inhibition by blocking the catalytic Cys145 of M pro . Using a combination of crystal structures and LC−MS data, we showed that M pro hydrolyzes the new ebselen derivative and leaves behind selenium (Se) bound with Cys145 of the catalytic dyad of M pro . We also described the binding profile of ebselen-based inhibitors using molecular modeling predictions supported by binding and inhibition assays. Furthermore, we have also solved the crystal structure of catalytically inactive mutant H41N-M pro , which represents the inactive state of the protein where the substrate binding pocket is blocked. The inhibited structure of H41N-M pro shows gatekeeper residues in the substrate binding pocket responsible for blocking the substrate binding; mutation of these gatekeeper residues leads to hyperactive M pro .

To date, organoseleniums are pre-eminent for peroxide decomposing and radical quenching antioxidant activities. On the contrary, here a series of Janus-faced aminophenolic diselenides have been prepared from substituted 2-iodoaniline and...

A one pot Cu(I)-assisted synthetic methodology has been developed for the preparation of biologically important C2-symmetric spirodiaza, benzyloxy, benzoxytelluranes from 2-bromo-N-aryl benzamides, benzyl alcohols, and benzoic acid by using tellurium...