Bidentate Ligand Driven Intramolecularly Te O Bonded Organotellurium Cations from Synthesis, Stability to Catalysis.

A new series of unsymmetrical phenyl tellurides derived from 2-N-(quinolin-8-yl) benzamide ligand has been synthesized in a practical manner by the copper-catalyzed method by using diaryl ditelluride and Mg as a reductant at room temperature. In order to augment the Lewis acidity of these newly formed unsymmetrical monotellurides, these have been transformed into corresponding unsymmetrical 2-N-(quinolin-8-yl)benzamide tellurium cations. Subsequently, these Lewis acidic tellurium cations were used as chalcogen bonding catalysts, enabling the synthesis of various substituted 1,2-dihydroquinolines by activating ketones with anilines under mild conditions. Moreover, the synthesized 2-N-(quinolin-8-yl)benzamide phenyl tellurium cation has also catalyzed the formation of ß-amino alcohols in high regioselectivity by effectively activating epoxides at room temperature. Mechanistic insight by 1 H and 19 F NMR study, electrostatic surface potential (ESP map), control reaction in which tellurium cation reacted explosively with epoxide, suggested that the enhanced Lewis acidity of tellurium center seems responsible for efficient catalytic activities under mild conditions enabling ß-amino alcohols with excellent regioselectivity and 1,2-dihydroquinolines with trifluoromethyl, nitro, and pyridylsubstitution, which were difficult to access.

Blue-Light Irradiated Mn(0)-Catalyzed Hydroxylation and C(sp3 )-H Functionalization of Unactivated Alkanes with C(sp2 )-H Bonds of Quinones for Alkylated Hydroxy Quinones and Parvaquone.

Site-selective C(sp3 )-H functionalization of unreactive hydrocarbons is always challenging due to its inherited chemical inertness, slightly different reactivity of various C-H bonds, and intrinsically high bond dissociation energies. Here, a site-selective C-H alkylation of naphthoquinone with unactivated hydrocarbons using Mn2 (CO)10 as a catalyst under blue-light (457 nm) irradiation without any external acid or base and pre-functionalization is presented. The selective C-H functionalization of tertiary over secondary and secondary over primary C(sp3 )-H bonds in abundant chemical feedstocks was achieved, and hydroxylation of quinones was realized in situ by employing the developed methodology. This protocol provides a new catalytic system for the direct construction of high-value-added compounds, namely, parvaquone (a commercially available drug used to treat theileriosis) and its derivatives under ambient reaction conditions. Moreover, this operationally simple protocol applies to various linear-, branched-, and cyclo-alkanes with high degrees of site selectivity under blue-light irradiated conditions and could provide rapid and straightforward access to versatile methodologies for upgrading feedstock chemicals. Mechanistic insight by radical trapping, radical scavenging, EPR, and other controlled experiments well corroborated with DFT studies suggest that the reaction proceeds by a radical pathway.

Directing Group Strategy for the Isolation of Organoselenium(VI) Benzoselenonates: Metal-Free Catalysts for Hydrogen Evolution Reaction.

The exploration of fourth-period organoelements, particularly organoseleniums in their highest VI oxidation state, is limited owing to their stability and synthesis. Herein, the isolation of a new class of quinolinyl-embedded, hexavalent selenium(VI) benzoselenonates has been discussed and further evaluated for a metal-free electrocatalytic hydrogen evolution reaction (HER). The Se(VI) benzoselenonates exhibited high Faradaic efficiency (F.E.) of metal-free H2 gas production up to 86% with a very good turnover number (TON) up to 43 and moderate overpotential (η) of 500 mV; in the presence of mild acetic acid source in a less deprotonating DMF solvent. Taken together with various (NMR, UV-vis, and EPR) spectroscopic and DFT computation studies, a plausible HER pathway is proposed, which suggests that the electrochemical reduction of quinolinyl ring is the initiation step and Se(VI) acts as the reaction site by involving a hydridic type of intermediate for the electrochemical H2 gas generation.

2-Benzamide Tellurenyl Iodides: Synthesis and Their Catalytic Role in CO2 Mitigation.

Benzamide-derived organochalcogens (chalcogen=S, Se, and Te) have shown promising interest in biological and synthetic chemistry. Ebselen molecule derived from benzamide moiety is the most studied organoselenium. However, its heavier congener organotellurium is under-explored. Here, an efficient copper-catalyzed atom economical synthetic method has been developed to synthesize 2-phenyl-benzamide tellurenyl iodides by inserting a tellurium atom into carbon-iodine bond of 2-iodobenzamides in one pot with 78-95 % yields. Further, the Lewis acidic nature of Te center and Lewis basic nature of nitrogen of the synthesized 2-Iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides enabled them as pre-catalyst for the activation of epoxide with CO2 at 1 atm for the preparation of cyclic carbonates with TOF and TON values of 1447 h-1 and 4343, respectively, under solvent-free conditions. In addition, 2-iodo-N-(quinolin-8-yl)benzamide tellurenyl iodides have also been used as pre-catalyst for activating anilines and CO2 to form a variety of 1,3-diaryl ureas up to 95 % yield. The mechanistic investigation for CO2 mitigation is done by 125 Te NMR and HRMS studies. It seems that the reaction proceeds via formation of catalytically active Te-N heterocycle, an ebtellur intermediate which is isolated and structurally characterized.

Coordination Behavior of the Tellurium Incorporated Mercuraazametallamacrocycle and Investigation of d10 ⋠⋠⋠d10 Interactions between Closed Shell (Ag+ Hg2+ ) Metal Ions.

Herein, a new tellurium and mercury containing mercuraazametallamacrocycle has been prepared via (2+2) condensation of bis(o-aminophenyl)telluride and bis(o-formylphenyl)mercury(II). The isolated bright yellow solid of mercuraazametallamacrocycle has adopted unsymmetrical figure-of-eight conformation in the crystal structure. To study the metallophilic interactions between closed shell metal ions, the macrocyclic ligand has been treated with two equiv. of AgOTf (OTf=trifluoromethansulfonate) and AgBF4 , which afforded greenish-yellow bimetallic silver complexes. The isolated silver complexes displayed intramolecular Hg⋅⋅⋅Ag, Te⋅⋅⋅Ag interactions as well as intermolecular Hg⋅⋅⋅Hg interactions and formed an extended 1D molecular chain by directing six atoms to interact as TeII ⋅⋅⋅AgI ⋅⋅⋅HgII ⋅⋅⋅HgII ⋅⋅⋅AgI ⋅⋅⋅TeII in a non linear fashion. The Hg⋅⋅⋅Ag, Te⋅⋅⋅Ag interactions have also been studied in solution by 199 Hg, 125 Te NMR spectroscopy, absorption, and emission spectroscopy. In DFT calculations, the Atom in Molecule (AIM) analysis, non-covalent interactions (NCI), natural bonding orbital (NBO) analysis strongly supported for experimental evidences and revealed that the intermolecular Hg⋅⋅⋅Hg interaction is stronger than the intramolecular Hg⋅⋅⋅Ag interactions.

Blue Light Irradiated Metal-, Oxidant-, and Base-Free Cross-Dehydrogenative Coupling of C(sp2)-H and N-H Bonds: Amination of Naphthoquinones with Amines.

Herein, we report a blue-light-driven amination of C(sp2)-H bond of naphthoquinones and quinones with the N-H bond of primary and secondary amines for the synthesis of 2-amino-naphthoquinones and 2-amino-quinones. The coupling of naphthoquinones with a wide array of aliphatic, aromatic, chiral, primary, and secondary amines having electron donating (-CH3, -OCH3, -SCH3), withdrawing (-F, -Cl, -Br, -I), and CO2H, -OH, -NH2 groups with acidic protons selectively occurred to afford C-N coupled 2-amino-naphthoquinones in 60-99% yields and hydrogen gas as a byproduct in methanol solvent without using any additional reagents, additives, and oxidant under the blue light irradiation. Mechanistic insight by DFT computation, controlled experiments, kinetic isotopic effect, and substitution effect of the substrates suggest that the reaction proceeds by radical pathway in which naphthoquinone forms a highly oxidizing naphthoquinonyl biradical upon irradiation of blue light (457 nm). Consequently, electron transfer from electron-rich amine to an oxidizing naphthoquinonyl biradical leads to a naphthoquinonyl radical anion and aminyl radical cation, followed by proton transfer and delocalization leading to a carbon-centered naphthoquinonyl radical. The cross-coupling of naphthoquinonyl carbon-centered and aminyl nitrogen radicals forms a C-N bond, with subsequent elimination of hydrogen gas (which was also confirmed by GC-TCD), affording 2-amino-1,4-naphthoquinone under metal-, reagent-, base-, and oxidant-free conditions.

Detailed Insights into the Inhibitory Mechanism of New Ebselen Derivatives against Main Protease (Mpro) of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2).

SARS-CoV-2 main protease (Mpro/3CLpro) 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 Mpro, which affects its enzymatic activity and virus survival. Herein, we synthesized various ebselen derivatives to understand the mechanism of Mpro inhibition by ebselen. Using ebselen derivatives, we characterized the detailed interaction mechanism with Mpro. We discovered that modification of the parent ebselen inhibitor with an electron-withdrawing group (NO2) increases the inhibition efficacy by 2-fold. We also solved the structure of an Mpro complex with an ebselen derivative showing the mechanism of inhibition by blocking the catalytic Cys145 of Mpro. Using a combination of crystal structures and LC-MS data, we showed that Mpro hydrolyzes the new ebselen derivative and leaves behind selenium (Se) bound with Cys145 of the catalytic dyad of Mpro. 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-Mpro, which represents the inactive state of the protein where the substrate binding pocket is blocked. The inhibited structure of H41N-Mpro shows gatekeeper residues in the substrate binding pocket responsible for blocking the substrate binding; mutation of these gatekeeper residues leads to hyperactive Mpro.

Synthesis of cobalt(II) phenolate selenoether complexes to mimic hydrogenase-like activity for hydrogen gas production.

Selenium-derived electrocatalysts have been well explored for electrocatalytic hydrogen evolution reactions to mimic hydrogenase-like activity; however, the stability of these synthetic mimics is yet to be enhanced. In this study, we report the synthesis and characterization of a series of 1,10-phenanthroline-cobalt(II) phenolate selenoether complexes using 1,10-phenanthroline and 6-nitro-1,10-phenanthroline-Co(II)-dichloride and substituted bis-selenophenolate ligands. The synthesized cobalt(II) phenolate selenoether complexes have been characterized by CHN analysis, mass spectrometry, single crystal XRD, and UV-visible absorption spectroscopy. These complexes show electrocatalytic proton reduction from acetic acid at an overpotential of 0.45-0.56 V vs. Fc+/Fc and surpass previously reported selenium and sulfur-containing electrocatalysts. Furthermore, gas analysis from control potential electrolysis confirms that the cobalt(II) selenoethers act as electrocatalysts to produce H2 with a faradaic efficiency of 43-83% and show a turnover number of 3.24-58.60 molcat-1. The hydrogen evolution reaction (HER) was probed using deuterated acetic acid, which demonstrates an inverse kinetic isotopic effect (KIE) and is consistent with the formation of metal hydride intermediates. Furthermore, control experiments (post-dip analysis and multiple CV studies) have been performed to support the catalysis being due to a homogeneous process. Acid titration using UV-visible spectroscopy reveals that protonation is the prior step for electrocatalysis and assists in the formation of a cobalt hydride intermediate, which upon reaction with a proton generates hydrogen gas.

Light-Driven Carbon-Carbon Coupling of α-sp3-CH of Aliphatic Alcohols with sp2-CH Bond of 1,4-Naphthoquinones.

Here, an α-selective Csp3-H bond functionalization of primary aliphatic alcohols with 1,4-naphthoquinones yielded Csp2-Csp2 coupled products driven by blue-LED light under catalyst, metal, base, and reagent-free conditions. In this transformation, cleavage of three C-H bonds (two sp3-C-H, one sp2-C-H, and one O-H) and four new bonds formed, leading to fluorescent 2-acylated-1,4-naphthohydroquinones.

A base-free copper-assisted synthesis of C2-symmetric spirotelluranes and biaryls based on divergent stoichiometry of Na2Te.

A one pot Cu(I)-assisted synthetic methodology has been developed for the preparation of biologically important C2-symmetric spirodiaza, benzyloxy and benzoxytelluranes from 2-bromo-N-aryl benzamides, benzyl alcohols, and benzoic acids by using the tellurium dianion (Te2-) under base-free conditions. Furthermore, C-C coupled biaryl 1,1'-diamides have been prepared by using an excess of Na2Te under the same reaction conditions. The synthesized spirodiazatelluranes served as a potent catalyst for the reduction of H2O2 and nitro-Michael reactions.

Tetravalent Spiroselenurane Catalysts: Intramolecular Se···N Chalcogen Bond-Driven Catalytic Disproportionation of H2O2 to H2O and O2 and Activation of I2 and NBS.

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 8-aminoquinoline ligand. Further, the synthesized spiroselenuranes, when assayed for their antioxidant activity, show disproportionation of hydrogen peroxide into H2O and O2 with first-order kinetics with respect to H2O2 for the first time by any organoselenium molecules as monitored by 1H NMR spectroscopy. Electron-donating 5-methylthio-benzamide ring-substituted spiroselenurane disproportionates hydrogen peroxide at a high rate of 15.6 ± 0.4 × 103 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 H2O2 at rates of 7.9 ± 0.3 × 103 and 2.9 ± 0.3 × 103 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 H2O2 has also been confirmed by a gas chromatograph-thermal conductivity detector (GCTCD) and a portable digital polarographic dissolved O2 probe. Additionally, the synthesized spiroselenuranes exhibit thiol peroxidase antioxidant activities for the reduction of H2O2 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 I2 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 77Se NMR, mass spectrometry, UV-visible spectroscopy, single-crystal 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 H2O2, I2, and NBS. The reaction of H2O2, I2, 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.

Isolation of monomeric copper(II) phenolate selenoether complexes using chelating ortho-bisphenylselenide-phenolate ligands and their electrocatalytic hydrogen gas evolution activity.

A series of novel copper(II) phenolate selenoether complexes have been synthesized and structurally characterized for the first time from copper(I) phenanthroline and various substituted ortho-bisphenylselenide-phenol chelating ligands. The synthesized complexes exhibit Jahn-Teller distortion in their geometry and varied from distorted square planar to distorted octahedral by varying the substituent in the bis-selenophenolate ligand. The synthesized complexes electrocatalyze the hydrogen evolution reaction (HER) with a faradaic efficiency of up to 89%, and it was observed that the distorted square pyramidal geometry is the optimum geometry for the maximum efficiency of these copper complexes.

Proton reduction by a bimetallic zinc selenolate electrocatalyst.

The development of alternative energy sources is the utmost priority of developing society. Unlike many prior homogeneous electrocatalysts that rely on a change in the oxidation state of the metal center and/or electrochemically active ligand, here we report the synthesis and structural characterization of a bimetallic zinc selenolate complex consisting of a redox silent zinc metal ion and a tridentate ligand that catalyzes the reduction of protons into hydrogen gas electrochemically and displays one of the highest reported TOF for a homogeneous TM-metal free ligand centered HER catalyst, 509 s-1. The current-voltage analysis confirms the onset overpotential of 0.86 V vs. Ag/AgCl for the HER process. Constant potential electrolysis (CPE) has been carried out to study the bulk electrolysis of our developed protocol, which reveals that the bimetallic zinc selenolate catalyst is stable under cathodic as well as anodic potentials and generates hydrogen gas with a faradaic efficiency of 75%. Preliminary studies on the heterogeneous catalyst were conducted by depositing the bimetallic zinc selenolate catalyst on the electrode surface.

Janus -faced oxidant and antioxidant profiles of organo diselenides.

To date, organoseleniums are pre-eminent for peroxide decomposition and radical quenching antioxidant activities. On the contrary, here, a series of Janus-faced aminophenolic diselenides have been prepared from substituted 2-iodoaniline and selenium powder using copper-catalyzed methodology. Subsequently, condensation with substituted salicylaldehyde afforded the Schiff base, which on reduction, yielded the desired substituted aminophenolic diselenides in 72%-88% yields. The generation of reactive oxygen species (ROS) from oxygen gas by the synthesized aminophenolic diselenides was studied by analyzing the oxidation of dichlorofluorescein diacetate (DCFDA) dye and para-nitro-thiophenol by fluorescence and UV-Visible spectroscopic methods. Furthermore, density functional theory calculations and crystal structure analysis revealed the role of functional amine and hydroxyl sites present in the Janus-faced organoselenium catalyst for the activation of molecular oxygen, where NH and phenolic groups bring the oxygen molecule close to the catalyst by N-H⋯O and O-H⋯O intermolecular interactions. Additionally, these functionalities stabilize the selenium-centered radical in the formed transition states. Antioxidant activities of the synthesized diselenides have been explored as the catalyst for the decomposition of hydrogen peroxide using benzenethiol sacrificial co-reductant by a well-established thiol assay. Radical quenching antioxidant activity was studied by the quenching of DPPH radicals at 516 nm by UV-Visible spectroscopy. The structure activity correlation suggests that the electron-rich phenol and electron-rich and sterically hindered selenium center enhance the oxidizing property of the aminophenolic diselenides. Janus-faced diselenides were also evaluated for their cytotoxic effect on HeLa cancer cells via MTT assay, which suggests that the compounds are effective at 15-18 µM concentration against cancer cells. Moreover, the combination with therapeutic anticancer drugs Erlotinib and Doxorubicin showed promising cytotoxicity at the nanomolar concentration (8-28 nM), which is sufficient to suppress the growth of the cancer cells.

Radical Chain Breaking Bis(ortho-organoselenium) Substituted Phenolic Antioxidants.

The presence of a chalcogen atom at the ortho-position of phenols enhances their radical chain-breaking activity. Here, a copper(I)-catalyzed reaction of 2,6-dibromo- and 2,6-diiodophenols with diorganodiselenides has been studied for the introduction of two organoselenium substituents at both ortho-positions of the phenolic radical chain-breaking antioxidants, which afforded 2,6-diorganoseleno-substituted phenols in 80-92% yields having electron-donating CH3 , and electron-withdrawing CN and CHO functionalities. Additionally, 2,6-diiodophenols with electron-withdrawing CHO and CN groups also afforded novel 5,5'-selenobis(4-hydroxy-3-(phenylselanyl)benzaldehyde) and 5,5'-selenobis(4-hydroxy-3-(phenylselanyl)benzonitrile) consisting of three selenium and two phenolic moieties along with 2,6-diorganoseleno-substituted phenols has been synthesized. The electron-withdrawing CHO group has been reduced by sodium borohydride to the electron-donating alcohol CH2 OH group, which is desirable for efficient radical quenching activity of phenols. The developed copper-catalyzed reaction conditions enable the installation of two-arylselenium group ortho to phenolic radical chain-breaking antioxidants, which may not be possible by conventional organolithium-bromine exchange methods due to the sluggish reactivity of trianions (dicarba and phenoxide anion), which are generated by the reaction of organolithium with 2,6-dibromophenols, with diorganodiselenides. The antioxidant activities of the synthesized bis and tris selenophenols have been accessed by DPPH, thiol peroxides, and singlet oxygen quenching assay. The radical quenching antioxidant activity has been studied for the synthesized compounds by 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. The bis-selenophenols show comparable radical deactivating activity, while tris seleno-bisphenols show higher radical deactivating activity than α-tocopherol. Furthermore, the tris seleno-bisphenol shows comparable peroxide decomposing activity with ebselen molecules.

Synthesis of Chiral-Substituted 2-Aryl-ferrocenes by the Catellani Reaction.

A palladium-catalyzed and norbornene-mediated methodology has been developed for the synthesis of chiral 2-aryl-ferroceneamides from chiral 2-iodo-N,N-diisopropylferrocencarboxamide, iodoarenes, and alkenes using a JohnPhos ligand and potassium carbonate as a base in dimethylformamide at 105 °C. The developed three-component coupling protocol allows the compatibility of electron-withdrawing fluoro, chloro, ester, and nitro and electron-donating methyl, methoxy, dimethoxy, benzyl ether-substituted iodo-benzenes, other iodoarenes, such as iodo-naphthalene, heteroarenes, such as iodothiophene, and terminating substrates, such as methyl, ethyl, tert-butyl acrylates, and substituted styrenes with 2-iodo-N,N-diisopropylferrocencarboxamide. Furthermore, the developed three-component Catellani method proceeded with the retention of the configuration of the planar chiral ferrocene, which depends on the role of the participating carbon-iodine bond in ferrocene. Consequently, the developed protocol enabled the formation of densely substituted chiral 2-aryl ferroceneamides, exhibiting good to excellent enantioselectivity. The conversion of an ester of the synthesized chiral 2-aryl ferroceneamides has also been carried out to further accommodate the easily expendable acid and alcohol functionalities.

8-Aminoquinoline-Assisted Synthesis and Crystal Structure Studies of Ferrocenyl Aryl Sulfones.

A copper-catalyzed 8-aminoquinoline-directed oxidative cross-coupling of the C-H bond of ferrocene with sodium arylsulfinates has been achieved. The robust copper catalyst tolerates a range of methyl, tert-butyl, bromo, chloro, iodo and nitro functional groups in the phenyl ring, and set the stage for the synthesis of substituted ferrocene sulfones. Furthermore, X-ray crystal structure study on several ferrocenyl sulfones reveals the tetrahedral geometry around sulfur; interestingly, the O-S-O angle is larger than the electropositive substituent C-S-C angle which could be explained by Bent's rule. Further, unusual intramolecular O(S)⋅⋅⋅N(amide) short contacts (2.925-3) and O(S)⋅⋅⋅C=O were also noticed in ferrocenyl sulfones.

Copper-Mediated Selective Mono- and Sequential Organochalcogenation of C-H Bonds: Synthesis of Hybrid Unsymmetrical Aryl Ferrocene Chalcogenides.

An 8-aminoquinoline-directed, copper/1,10-phenanthroline-mediated selective mono-organothiolation of the C-H bond in ferroceneamide has been developed using aryl/alkyl disulfide substrates. The sequential ferrocene C-H organochalcogenation (chalcogen = S, Se, and Te) has also been established for the synthesis of novel hybrid unsymmetrical aryl chalcogenides with the aid of a catalytic amount of Cu(OAc)2 under ambient reaction conditions. The developed protocol results in a broad functional group tolerance to allow alkyl-, aryl-, heteroaryl-, bromo-, chloro-, and nitro-containing diorgano dichalcogenides as coupling partners. Furthermore, the 8-aminoquinoline directing group is easily removed to afford the aldehyde functionality after C-H organochalcogenation. A mechanistic understanding of the copper-mediated selective mono-organothiolation reaction suggests that the rigid bicoordinated 1,10-phenanthroline ligand and freshly generated copper(II) from Cu(I) in the less polar solvent acetonitrile are crucial to the selective mono-C-H functionalization of ferroceneamide.

An efficient copper-catalyzed synthesis of symmetrical bis(N-arylbenzamide) selenides and their conversion to hypervalent spirodiazaselenuranes and hydroxy congeners.

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. The developed protocol tolerates substituents in both N-aryl and benzamide rings of the 2-halobenzamide substrates and provides an array of bis(N-arylbenzamide) selenides in practical yields. The resulting selenides were transformed into hypervalent spirodiazaselenuranes by oxidation using aqueous hydrogen peroxide. (N-(1-Naphthyl)) spirodiazaselenurane is also structurally characterized by a single crystal X-ray study. Hydroxy-substituted spiroselenuranes have been prepared by careful demethylation of methoxy-substituted selenides followed by oxidation by hydrogen peroxide. Antioxidant properties for the decomposition of hydrogen peroxide and for the deactivation of radicals of hydroxy-substituted spiroselenuranes have been studied by the thiol assay and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay. Both hydroxy-substituted spiroselenuranes exhibit dual mimic functions of glutathione peroxidase (GPx) selenoenzyme and α-tocopherol for decomposition of hydrogen peroxide and deactivation of radicals, respectively.

An Organodiselenide with Dual Mimic Function of Sulfhydryl Oxidases and Glutathione Peroxidases: Aerial Oxidation of Organothiols to Organodisulfides.

A novel organodiselenide, which mimics sulfhydryl oxidases and glutathione peroxidase (GPx) enzymes for oxidation of thiols by oxygen and hydrogen peroxide, respectively, into disulfides has been presented. The developed catalyst oxidizes an array of organothiols into respective disulfides in practical yields by using aerial O2 to avoid any reagents/additives, base, and light source. The synthesized diselenide also catalyzes the reduction of hydrogen peroxide into water by following the GPx enzymatic catalytic cycle with a reduction rate of 49.65 ± 3.7 µM·min-1.