The electrochemical behaviour of [2H] benziso-1,2-selenazol-3-one (2b) in non aqueous media was studied using a platinum electrode. The corresponding Se-monoxide 3 was isolated and characterised. Comparison with [2H] benziso-1,2-thiazol-3-one (2a), [3H] benzo-1,2-dithiol-3-one (4a) and [3H] benzo-2,1-thioselenol-3-one (4b) was performed. In the case of compounds 2a,b the impact of the availability of the lone pair of the nitrogen atoms adjacent to the selenium atom on the electrochemical behaviour is discussed.

The electrochemical behaviour of [2H]benziso-1,2-thiazol-3-one in non-aqueous media has been studied using platinum electrode. A new indirect electrochemical synthesis of [2H]benziso-1,2-thiazol-3-one S-oxide mediated by chloride anion was performed in quantitative yield.

The electrochemical oxidation of 2-phenyl-1,2-benzisoselenazol-3(2H)-one and several of its derivatives was investigated in dried acetonitrile by conventional and microelectrode techniques. The unsubstituted benzisoselenazolone (1a) as well as its derivatives substituted in position 4′ by methyl (1b) and methoxy (1c) groups are oxidized by controlled potential electrolysis into their selenoxides (2a–c). The intermediary cation radicals (CRs), eventually stabilized in the medium by addition of a water scavenger (trifluoroacetic anhydride, 1%), were detected by high-speed cyclic voltammetry at potential scan rates up to 30 kV s−1. The corresponding reaction mechanism is of an ECE-type, in which the chemical step consists of the hydrolysis of the formed CR by residual water. A comparison with its sulphur analogues, 2-phenyl-1,2-benzisothiazol-3(2H)-ones (3), showed that the selenium CRs are three orders of magnitude more reactive towards residual water then their sulphur analogues. Similar studies of benzisoselenazolones substituted on the N-aryl ring by electro-donating groups, 2-(3,4-dimethoxyphenyl)- (1d), 2-(3,4-methylenedioxyphenyl)- (1e) and 2-(4-dimethylaminophenyl)-1,2-benzisoselenazolone (1f), gave rise to no selenoxide formation, although intermediary CRs were detected at potential scan rates below 30 V s−1.

The electrochemical oxidation of dibenzo(c,e)-1,2-diselenine (1a) in dry acetonitrile was studied by conventional and microelectrode techniques. Steady-state voltammetry and cyclic voltammetry proved the occurrence of an electro-chemical-electronic (ECE)-type mechanism for the first oxidation signal. The chemical step involves the reaction of the cation radical with residual water. The first electron transfer proceeds with a heterogeneous rate constant of 0.14 ± 0.01 cm s−1, whereas a pseudo-first-order kinetic rate constant of 20.7 ± 2.8 s−1 is computed for the chemical step, giving a half-life of 33 ± 4 ms for the cation radical of 1a. A comparison of these two rate constants with those of dibenzo(c,e)-1,2-dithiin (1b), selenanthrene (2a) and thianthrene (2b) indicates that the electron transfer rate depends on the nature of the oxidized chalcogen, whereas the stabilization of the cation radical is also dependent on the geometry of the heterocycle.

The electrochemical behaviour of 2-(benzylseleno)benzanilide was investigated by voltammetry using a rotating platinum electrode, cyclic voltammetry, controlled potential coulometry and electrolysis. The measurements were made in acetonitrile medium. Comparison in terms of potential values and obtained products were made between 2-(benzylseleno)benzanilide, benzyl phenyl selenide and their sulphur analogues.

The electrochemical behaviour of benzyl phenyl selenide was investigated by voltammetry using a rotating platinum disk electrode, cyclic voltammetry, controlled potential coulometry and electrolysis. The measurements were made in acetonitrile solution. In contrast to the case of benzyl phenyl sulfide, the oxidation products diphenyl diselenide, benzaldehyde and N-benzylacetamide result from the evolution of benzyl phenyl selenoxide and not from the corresponding initially formed radical cation

A series of triterpene compounds characterized by a stringent structure-activity relationship were identified as potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) replication. Currently studied botulinic derivatives have 50% inhibitory concentrations (IC50) against HIV-1 strain IIIB/LAI in the 10 nM range in several cellular infection assays but are inactive against HIV-2. These compounds did not significantly inhibit the in vitro activities of several purified HIV-1 enzymes. Rather, they appeared to block virus infection at a postbinding, envelope-dependent step involved in the fusion of the virus to the cell membrane.

The electrochemical behaviour of 2-(benzylseleno)benzanilide was investigated by voltammetry using a rotating platinum electrode, cyclic voltammetry, controlled potential coulometry and electrolysis. The measurements were made in acetonitrile medium. Comparison in terms of potential values and obtained products were made between 2-(benzylseleno)benzanilide, benzyl phenyl selenide and their sulphur analogues.

The electrochemical oxidation of thioselenanthrene (1c) in acetonitrile was studied by conventional and microelectrode techniques. Steady-state and cyclic voltammetry proved the occurrence of a DISP2 mechanism for the first oxidation signal. Controlled potential coulometry led to the formation of the corresponding selenoxide. The first electron transfer proceeds with a high heterogeneous rate constant (0.58 ± 0.10 cm s−1), whereas a pseudo-first-order apparent rate constant of 8.87 ± 1.11 s−1 was computed for the chemical step, giving a half-lifetime of 78 ± 10 ms for the cation-radical of 1c. In order to compare their cation-radical stabilities, similar measurements were also realized for phenoxathiine (1d) and phenoxaselenine (1e).

The electrochemical behaviour of 2-(methylseleno)benzanilide, one of the major metabolites of Ebselen, together with a series of 2-methylseleno-(4′-X-phenyl)benzamides were investigated by voltammetry using a rotating platinum electrode, cyclic voltammetry, controlled potential coulometry and electrolysis. The measurements were realized in acetonitrile solution. The influence of temperature and acid on the nature of the oxidized products is shown. Comparison with their thio analogs is discussed.

The electrochemical oxidation of 2-phenyl-1.2-benzisothiazol-3(2H)-ones and related compounds in acetonitrile solution was studied by voltammetry using a rotating platinum electrode, cyclic voltammetry, controlled potential coulometry and electrolysis. Further oxidation of studied compounds gave the corresponding sulfoxide. Comparison of the cyclic compound and related open-chain compounds was discussed.

The electrochemical oxidation of dibenzo(c,e)-1,2-diselenine 1b has been investigated in acetonitrile medium by voltammetry at rotating platinum electrode, cyclic voltammetry and constant potential coulometry. The exhaustive oxidation of compound 1b exclusively leads to the formation of the monoxide of dibenzo(b, d)selenophene with concomitant extrusion of selenium dioxide. The influence of the duration and the temperature of the electrolysis is reported. Each step of the electrochemical oxidation is described in detail. Comparison with the chemical and electrochemical oxidation of dibenzo)c, e)-1,2-dithiine and the chemical oxidation of cyclic vic-diselenide is discussed.

The electrochemical oxidation of benzo(b)selenophene and dibenzo(b,d)selenophene in non-aqueous media has been studied using platinum and glassy carbon electrodes. The selenoxide of dibenzo(b,d)selenophene has been isolated. A mechanism consistent with voltammetric measurements has been established. The electrochemical oxidation of dibenzo(b,d)thiophene was discussed and compared with its seleno analog.

The electrochemical properties of dibenzo(c,e)-1,2-dithiin in acetonitrile solution are investigated by voltammetry at rotating platinum and vitrous carbon disk electrodes, and by cyclic voltammetry and constant potential coulometry. Attention is particularly devoted to the first charge transfer step and the subsequent chemical reactions. Evidence for an ECE process is given. Comparison of the chemical and electrochemical oxidation of dibenzo(c,e)-1,2-dithiin and related open-chain compounds is discussed.

Abstract The electrochemical oxidation of dibenzo(c, e)-1,2-diselenine 1b has been investigated in acetonitrile medium by voltammetry at rotating platinum electrode, cyclic voltammetry and constant potential coulometry. The exhaustive oxidation of compound 1b exclusively leads to the formation of the monoxide of dibenzo(b, d)selenophene with concomitant extrusion of selenium dioxide. The influence of the duration and the temperature of the electrolysis is reported. Each step of the electrochemical oxidation is described in detail. Comparison with the chemical and electrochemical oxidation of dibenzo(c, e)-1,2- dithiine and the chemical oxidation of cyclic vic-diselenide is discussed.

The electrochemical oxidation of benzo(b)selenophene and dibenzo(b,d)selenophene in nonaqueous media has been studied using platinum and glassy carbon electrodes. The selenoxide of dibenzo(b,d)selenophene has been isolated. A mechanism consistent with voltammetric measurements. has been established. The electrochemical oxidation of dibenzo(b,d)thiophene was discussed and compared with its seleno analog.

The bimolecular rate constants (k) of quenching of molecular singlet oxygen 1O2 (1 delta g) by organo-selenium compounds exhibiting glutathione peroxidase activity and by sulfur analogs have been determined by time resolved phosphorescence detection of 1O2 in CD3OD and C6D6, with no solvent effect. The rate constants of quenching by the Se-containing compounds were found to be approximately one order of magnitude higher than those of the S-containing homologs. A linear correlation was observed between log k and the Hammett constant omega ortho with p = -0.89, the rate constant being higher for molecules with an electron-donating substituent and lower for those with an electron-withdrawing substituent. This observation is consistent with the involvement of a charge transfer complex in the deactivation of singlet oxygen.

The electrochemical behaviour of 7-substituted benzisoselenazol-3-(2H)-ones (BISAs) was investigated by voltammetry using a rotating platinum electrode, cyclic voltammetry, controlled potential coulometry and electrolysis. The measurements were realized in “dry” neutral and acidic acetonitrile. Further oxidation od studied compounds gives the corresponding selenoxide. The role played by the protons during the reduction of this selenoxide has been demonstrated. The presence of a substituent in the 7-position of the benzisoselenazolin-3-one system strongly influence the values of the first oxidation potential. The nature of this interaction is discussed. A good correlation between thr first oxidation potential and the σortho Hammett coefficient is obtained. These results provide further evidence for the lack of association between the direct oxidation of BISAs into the corresponding selenoxide and the high (GSP-Px)-like activity of the 7-substituted BISAs.

The electrochemical properties of selenoxanthene, selenoxanthene-9-ol and selenoxanthone in non-aqueous and mixed media are investigated by voltammetry at rotating platinum and vitrous carbon disk electrodes, cyclic voltammetry, chronopotentiometry and constant potential coulometry. In “dry” acetonitrile selenoxanthene leads to selenoxanthylium cation. In the presence of water, selenoxanthene-9-ol is obtained. Further oxidation of selenoxanthene-9-ol gives the selenoxanthone which can be oxidized to the corresponding selenoxide. Influence of acids and bases is shown.