Seleninic anhydride

An elegant application of Se NMR spectroscopy, in conjunction with N NMR spectroscopy, involves the detection of the thermally unstable eight-membered rings (RSeN)4 (3.13) from the reactions of a mixture of seleninic anhydrides (RSeO)20 (R=Ph, Pr) and N-enriched... 

Oximes, Hydrazones, and Semicarbazones.—Hydrazones and semicarbazones of 3-oxo-A - and -A -steroids may be smoothly converted into the parent ketones by treatment with benzene seleninic anhydride. ... 

A similar mechanism has also been proposed for deprotection of S,S -thioacetals using seleninic anhydride/ ... 

Reactions Involving Enols or Enolic Derivatives.—The full account was reported for the dehydrogenation of ketones using benzene seleninic anhydride.77 Further studies were reported on catalysts specific for the isomerization of A5-cholestenone to A4-cholestenone.78... 

Methods of synthesis of seleninic acids are based on oxidation of diselenides (or selenocyanates) with HNOj [38k, 42[ or H2O2 [23a, 42d, 43[. Seleninic anhydrides are prepared by dehydration of seleninic acids [42 e, 44[ or by oxidation of diselenides with ozone (Scheme 15.14) [44, 45]. 

Valerolactones.— The unstable dihydropyran anion (73) may be useful for the preparation of a-substituted valerolactones the intermediate dihydropyrans are converted into the latter by acid hydrolysis and Collins oxidation. A new route to the c/s-fused valerolactone portion of vemolepin has been developed which could have other applications. It has been briefly noted that benzene-seleninic anhydride can be used to dehydrogenate fused valerolactones to the a,j8-unsaturated derivatives the conditions, however, are somewhat drastic (120 °C, 42 h). Unsaturated valerolactones can also be obtained from vinyl-oxirans by a light-induced reaction with pentacarbonyliron followed by carbonyl-ation. ... 

Ketosteroids are smoothly oxidized to the l,4-dien-3-ones by benzene seleninic anhydride. Barton and his group have now made this reaction catalytic in selenium by developing the use of iodylarenes for the in situ oxidation of diphenyldiselenide to the anhydride. m-Iodylbenzoic acid was chosen to aid the isolation of the product and the recovery of the aryl iodide. 

---