Seleninate ester, formation

Treatment of the isomeric dihydroselenines 93 containing electron-withdrawing groups in both the 2- and 6-positions with w-chloroperbenzoic acid also leads to formation of Pummerer-type oxidation products, the 4H-selenines 94 and the corresponding w-chlorobenzoate ester by-products (Equation 39) <1999J(P1)1155>. The esters could be converted to the corresponding 477-selenines by treatment with polyphosphoric acid trimethylsilyl ester (PPSE), a useful reagent for eliminations under neutral conditions. These 4/7-selenines were key intermediates in the synthesis of selenabenzenes. 

Scheme 28, by application of the known thiol ester-thiopyrone phototransformation to selenium-containing systems. 5/f-[l]Benzoselenino[2,3-6]-pyridine, 4.ff-selenolo[2,3-6][l]benzoselenine, and 9/f-seleno[3,2-6][l]benzo-selenine have similarly been obtained by the corresponding selenol ester-seleninone conversion. Phenyl areneselenosulphonates undergo facile photo-induced homolysis of the selenium-sulphur bond in the presence of alkenes, a free-radical chain reaction leads to the formation of -phenylselenosulphones. ... 

Cyclic seleninate esters have been implicated in catalytic cycles in which diselenides act as glutathione peroxidase mimetics <2003JA13455> (see Section 9.15.11). Treatment of the diselenides 48 and 49 with excess / -rt-butylbydro-peroxide leads to the formation of the first unsubstituted isolable cyclic seleninates 50 and 51 (Equations 9 and 10). The six-membered ring compound 50 proved to be a less effective catalyst than 51 in the former reactions. 

The role played by benzeneseleninic acid or by phenylseleninyl chloride in promoting the rearrangement of A-aryl-benzohydroxamic acids PhOONArOH to p-hydroxy-benzanilides relies on the formation of seleninate or selenenate esters, respectively, followed by Claisen-type shifts to ortho- and then para-positions. ... 

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