Oxyselenides oxidation

The reaction of cyclohexene with AT-(phenylseleno)phthalimide in the presence of (S,S)-hydrobenzoin in methylene chloride afforded two diastereomeric oxyselenides (38 and the (li , 2R) diastereomer) in a 1 1 ratio. Compound 38 was separated and converted into the olefin 39 via selenoxide elimination. The second PhSeOTf promoted oxyselenenylation reaction gave only the cis fused bicyclic dioxane 40. Oxidation and subsequent elimination provided the olefin 41. This is the key intermediate for the syntheses of the cyclitols 42 and 43, that were obtained from a series of classical reactions as indicated in the Scheme. Oxyselenenylation reactions have also been employed to promote glycosylation reactions [43]. 

When the oxyselenides are further oxidized, PhSeOH is eliminated and allylic oxy-compounds are formed [58]. This procedure can be accomplished using catalytic amounts of PhSeSePh, as in Eq. (27) [59, 60],... 

Oxyselenides such as P40vSe and P40gSe3 have structures based on those of the oxides (Chapter 4.2). 

The reaction of the electrophilic selenium 450 with an olefin 451 and water or methanol produces the oxyselenide 452. Subsequent electrochemical oxidation of 452 provides the corresponding selenoxide 453 that undergoes a syn elimination to produce the desired trans product 454 and regenerates the selenenic acid 450. The addition of sulfate is crucial because it prevents the conversion of phenylselenenic acid into inert phenylseleninic acid by disproportionation or electro oxidation. 

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