2-Seleno-1-alkylbenzimidazoles and their diselenides: Synthesis and structural characterization of a 2-seleno-1-methylbenzimidazole complex of mercury

Abstract

2-Seleno-1-methylbenzimidazole, H(sebenzimMe), can be synthesized from 1-methylbenzimidazole by sequential treatment with (i) BunLi, (ii) elemental selenium and (iii) HCl(aq). This method is also applicable to the synthesis of 2-seleno-1-t-butylbenzimidazole, H(sebenzimBut). Single crystal X–ray diffraction and NMR spectroscopic data demonstrate that H(sebenzimMe) and H(sebenzimBut) exist as the selone rather than the selenol tautomers, which is in accord with the results of density functional theory (B3LYP) calculations. The data also indicate that the selone is best represented as a C+–Se− zwitterion rather than as a C=Se doubly bonded species. Aerobic oxidation of H(sebenzimMe) and H(sebenzimBut) in the presence of Et3N yields the diselenides, (sebenzimMe)2 and (sebenzimBut)2. In addition, H(sebenzimMe) reacts with HgCl2 to give [H(sebenzimMe)]2HgCl2, the first structurally characterized example of a 2-seleno-1-alkylimidazole mercury complex.

Stable and Persistent Acyclic Diaminocarbenes with Cycloalkyl Substituents and Their Transformation to β‐Lactams by Uncatalysed Carbonylation with CO

“…[3a] The distances are in between the values typical of carbon-selenium single and double bonds, which has been rationalised in terms of as ignificant contribution of zwitterionic structures that feature single N 2 C + ÀSe À dative bonds. [41] We finally come to the structures of the b-lactam derivatives 3a ( Figure 5) and 3c (see FigureS4i nt he Supporting Information) and to the structure of the hydrochloride 3bHCl ( Figure 6). For comparison, the structure of the hydrochloride of the b-lactam derivative obtainedb yc arbonylation of the "Alder carbene" (AHCl) is shown in FigureS5i nt he Supporting Information.…”

Total Synthesis and Functional Characterization of Selenoneine

“…[5] Selenols can efficiently react with triplet oxygen ( 3 O 2 )w hereas autoxidation of thiols usually depends on catalysis by transition metals. [6] Although diselenide bonds are more stable than disulfide bonds, [7] selenium generally forms weaker bonds with period 2e lements,a llowing selenium compounds to engage more readily in making and breaking covalent bonds.Because of this versatility selenium has also been included in the design of artificial enzymes, [8] enzyme models, [9] protein ligation strategies,p rotein folding studies, [7,10] or molecular probes. [11] Furthermore,t he observation that ebselen ( Figure 1a)a nd other synthetic organoselenides can catalyse peroxide reduction and form covalent bonds to specific proteins highlighted the therapeutic potential of such compounds.…”

“…Protocols to synthesize 2-mercaptoimidazoles, including ergothioneine are well established, [21] but these procedures invariably fail in the synthesis of 2-selenoimidazoles.Asuggested synthesis of selenoneine proved irreproducible in our hands and others. [20b,23] Approaches that were devised to make N-monosubstituted or N,N'-disubstituted 2selenoimidazoles are comparatively inefficient [9,22] and impose narrow restrictions on the range of permissible Nsubstituents.…”

Total Synthesis and Functional Characterization of Selenoneine

“…[6] Although diselenide bonds are more stable than disulfide bonds, [7] selenium generally forms weaker bonds with period 2 elements, allowing selenium compounds to engage more readily in making and breaking covalent bonds. Because of this versatility selenium has also been included in the design of artificial enzymes, [8] enzyme models, [9] protein ligation strategies, protein folding studies, [10] [7] or molecular probes. [11] Furthermore, the observation that ebselen ( Figure 1a) and other synthetic organoselenides can catalyse peroxide reduction and form covalent bonds to specific proteins highlighted the therapeutic potential of such compounds.…”

“…A suggested synthesis of selenoneine proved irreproducible in our hands and others. [20b, 22] Approaches that were devised to make N-monosubstituted or N,N'-disubstituted 2-selenoimidazoles are comparatively inefficient [9,23] and impose narrow restrictions on the range of permissible N-substituents.…”