Chemistry of biologically important synthetic organoselenium compounds.

2,3-Dihydroimidazol-2-ylidenes and their main group element chemistry

Chiral and achiral organochalcogen compounds bearing a heteroatom in close proximity are easily accessible via the directed aromatic lithiation route. The lithium chalcogenolates prepared by the insertion of selenium or tellurium into the C-Li bond are used to synthesize various chalcogen compounds such as Se/Te, N donor ligands, dichalcogenides, monomeric metal chalcogenolates, and macrocycles. The differences in the stability and reactivity of the organochalcogen compounds derived from various substrates are described in terms of electronic and stereochemical properties of donor atoms.

Heteroatom-directed aromatic lithiation: a versatile route to the synthesis of organochalcogen (Se, Te) compounds.

A survey of tellurium-centered secondary-bonding supramolecular synthons

Iodothyronine deiodinases (IDs) are mammalian selenoenzymes that catalyze the conversion of thyroxine (T4) to 3,5,3'-triiodothyronine (T3) and 3,3',5'-triiodothyronine (rT3) by the outer- and inner-ring deiodination pathways, respectively. These enzymes also catalyze further deiodination of T3 and rT3 to produce a variety of di- and monoiodo derivatives. In this paper, the deiodinase activity of a series of pen-substituted naphthalenes having different amino groups is described. These compounds remove iodine selectively from the inner-ring of T4 and T3 to produce rT3 and 3,3'-diiodothyronine (3,3'-T2), respectively. The naphthyl-based compounds having two selenols in the pen-positions exhibit much higher deiodinase activity than those having two thiols or a thiol selenol pair. Mechanistic investigations reveal that the formation of a halogen bond between the iodine and chalcogen (S or Se) and the pen-interaction between two chalcogen atoms (chalcogen bond) are important for the deiodination reactions. Although the formation of a halogen bond leads to elongation of the C-I bond, the chalcogen bond facilitates the transfer of more electron density to the C-I sigma* orbitals, leading to a complete cleavage of the C-I bond. The higher activity of amino-substituted selenium compounds can be ascribed to the deprotonation of thiol/selenol moiety by the amino group, which not only increases the strength of halogen bond but also facilitates the chalcogen chalcogen interactions.

Regioselective Deiodination of Thyroxine by Iodothyronine Deiodinase Mimics: An Unusual Mechanistic Pathway Involving Cooperative Chalcogen and Halogen Bonding

Tuning seleniumiodine contacts: from secondary soft–soft interactions to covalent bonds

The title compound, C9H11ISe, displays the following dimensions involving selenium: Se—I 2.5360 (11) A, Se—C1 1.923 (6) A and C—Se—I 100.2 (2)°. Short Se⋯I and I⋯I contacts link the mol­ecules into ribbons parallel to the b axis.

Mesityl­selenenyl iodide

Erratum to: ‘Tuning selenium–iodine contacts: from secondary soft–soft interactions to covalent bonds’ [Journal of Organometallic Chemistry 623 (2001) 14–28]

The report on recent preparative, n.m.r. spectroscopic and structural results concerning steric effects in organoselenium and -tellurium chemistry covers: 1. extremely bulky ditellurides and diselenides, including rotational barriers and unusual conformations, 2. bulky metal arylselenelolates and tellurolates, including compounds with bonds from Se or Te to Li, Na, K, Si, Ge, Sn, Zn, Cd, Hg and Au, 3. steric effects on silyltelluride/acyl halide and silylphosphane/tellurium reactions, 4. reaction of various diselenides and ditellurides with iodine and bromine, including iodine catalysis of Se-Se bond cleavage/bond formation equilibria.

Andreas Martens-von Salzen

Papers

Tuning seleniumiodine contacts: from secondary soft–soft interactions to covalent bonds

Mesitylselenenyl iodide

Erratum to: ‘Tuning selenium–iodine contacts: from secondary soft–soft interactions to covalent bonds’ [Journal of Organometallic Chemistry 623 (2001) 14–28]

New Sterically Congested Organoselenium and Tellurium Compounds

Andreas Martens-von Salzen

Papers

Tuning seleniumiodine contacts: from secondary soft–soft interactions to covalent bonds

Mesityl­selenenyl iodide

Erratum to: ‘Tuning selenium–iodine contacts: from secondary soft–soft interactions to covalent bonds’ [Journal of Organometallic Chemistry 623 (2001) 14–28]

New Sterically Congested Organoselenium and Tellurium Compounds

Mesitylselenenyl iodide