Aryl selenium compounds

Aryl selenium compounds also form adducts with hydrogen peroxide, ArSe (O)OOH, that are able to carry out epoxidation [188,189], albeit at low rates [190,191]. Improvements can be made by substitution of the aromatic ring with electron-withdrawing trifluoromethyl groups [192], for example, to form the lizs-[3,5-Ws-(trifluoromethyl)phenyl]diselenide. 

ArCHO — ArOH. Aromatic aldehydes undergo Baeyer-Villiger reaction when treated with H202 (30%) in the presence of several selenium compounds as catalysts, of which areneseleninic acids are most effective. The resulting aryl formates are readily hydrolyzed to phenols. 

Selenium analogues RN=SeCl2 are unknown for R = aryl or alkyl and thermally unstable when R = CE3 or C2E5. The perfluoroalkyl derivatives are prepared by the reaction of dichloroamino compounds and Sc2Cl2 in CCI3E (Eq. 8.18), but they decompose at room temperature to the corresponding diazene and a mixture of selenium chlorides. 

The addiction to nicotine that makes smoking withdrawal so difficult for many is believed to be mediated by a subset of nicotinic acetylcholine receptors. A bridged bicylcic aryl-benzepine that acts as a partial agonist at those sites is now approved as an aid for tobacco smoking withdrawal. The synthesis starts with the known ben-zonorbomenone (3-1). Treatment of that compound with selenium dioxide leads to the oxidation of the carbon adjacent to the carbonyl group and thus the formation... 

Recent progress on the use of hypervalent iodine reagents for the construction of heteroatom-heteroatom bonds is reviewed. Reactions of aryl-A3-iodanes with heteroatom substrates derived from third-row elements and beyond are considered first, and an unusual example of heteroatom-heteroatom bond formation with diaryliodonium salts is then discussed. Finally, the use of sulfonylimino(aryl)iodanes for imidations of phosphorus, sulfur, selenium, and arsenic compounds, including enantioselective transformations (S,Se), and alternate hypervalent iodine approaches to N-sulfonylsulfilimines and N-sulfonylarsinimines are summarized. 

The use of hypervalent iodine reagents for heteroatom-heteroatom bond forming reactions is well established in the context of classical oxidation chemistry [1-11]. For example, oxidations of anilines to azobenzenes, thiols to disulfides, and sulfides to sulfoxides with aryl-A3-iodanes were documented decades ago [1-5]. During the last ten years, particular attention has also been given to oxidative transformations of compounds derived from heavier elements, including the interception of reaction intermediates or initially formed products with external nucleophiles. A second important development is the utilization of sulfonyliminoiodanes, ArI = NS02R, for heteroatom-nitrogen bond formation, especially for imidations of sulfur, selenium, phosphorus and arsenic com-... 

Aryl-1,2,3-selenadiazoles upon prolonged heating are converted into selenophenes. Since the latter compounds have also been obtained from the reaction of arylalkynes with selenium, 1,2,3-selenadiazoles seem to be indirect precursors of selenophenes (Scheme 49) (73JHC953, 79JHC1405). 

Substitutions to halide compounds are the most typical reactions of nucleophilic selenium species (Scheme 18). Alkyl or aryl selenolates (R SeM), which are prepared in situ by the methods described in Sect. 2, react with halides to give... 

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