A variety of organo-sulfur, -selenium and -tellurium compounds can be oxidized to their corresponding higher oxidation state species. Thiols are reasonably stable in air and are oxidized by various reagents to disulfides (equation 1), while selenols, although isolable, are unstable in air and are oxidized readily to diselenides (equation 2). Tellurols are very sensitive to air and are normally present as ditellurides (equation 3). These disulfides, diselenides and ditellurides are further oxidized to various higher oxidation products depending on the specific reaction conditions. Sulfides (1; M = S), selenides (1; M = Se) and tellurides (1; M = Te) are generally oxidized to the corresponding sulfoxides (2; M = S), selenoxides (2; M = Se) and telluroxides (2; M = Te), which in turn are further oxidized to sulfones (3; M = S), selenones (3; M = Se) and tellurones (3; M = Te), respectively (Scheme 1). These oxidized species are also written in the alternative formats of (4) and (5), and syntheses of chiral sulfoxides and selenoxides by direct oxidation are known. A variety of chemical oxidizing agents can be employed for these transformations and some electrochemical, photochemical and enzymatic oxidations are also known.

Oxidation of Sulfur, Selenium and Tellurium

Organic selenium compounds: The chemical properties of some aryl selenonium compounds and the preparation of diaryl selenonium acetates

This review assembles the results of studies out in my laboratory and related to nucleophilic substitutions and cyclization reactions involving unsaturated and functionalized phenylsele-nides. Three modes of activation of the phenylselanyl group were used. The halogen treatment has produced dihalo adducts whose decomposition has led to various halogenated unsaturated and functionalized structures, sometimes with rearrangement. The PhSe+ activation was involved during the selenium-induced cyclization of homoallylic amines, allowing the formation of β-halopyrrolidines. The synthesis of aziridines was achieved, for the first time, through the intermediate formation of β-amino methylselenoniurn salts. Br+ and PhSe+ activations have also allowed the preparation of these azahetorocycles.

Inter and Intramolecular Nucleophilic Substitutions of Activated Phenylselanyl Groups

CHAPTER I - Organoselenium Oxidations

Hexafluoropropene oxide : a fluorinating reagent for the formation of element-fluorine bonds

CCXCIX.—The quadrivalency of selenium. Part III. The instability of the compounds of quadrivalent selenium derived from phenyl methyl and phenyl ethyl selenides and phenyl- and p-tolyl-seleno-glycollie acids

Owen Kempster Edwards

Papers

CCXCIX.—The quadrivalency of selenium. Part III. The instability of the compounds of quadrivalent selenium derived from phenyl methyl and phenyl ethyl selenides and phenyl- and p-tolyl-seleno-glycollie acids