Oxidation with benzeneseleninic anhydride

Phenylselenoenones can be prepared from allylic alcohols by oxidation with benzeneseleninic anhydride " or from enones by treatment with phenylselenyl... 

Dehydrogenation of 3-kelo steroids. The dehydrogenation of 3-keto steroids to l,4-diene-3-ones with benzeneseleninic anhydride (8, 31) can be carried out in comparable yield by use of a process in which the benzeneseleninic anhydride is used in catalytic amounts and is continuously regenerated from diphenyl diselenide by oxidation with iodylbenzene. In practice, m-iodylbenzoic acid is a more convenient reagent, since m-iodobenzoic acid is easily recovered. 12-Keto and 12-hydroxy steroids arc oxidized by the catalytic system to A9(1 - -keto steroids in high yield. In fact, methyl desoxycholate (1) can be oxidized in this way directly to the trienedione 2 in 64% yield.1... 

Little work appears to have been carried out with benzeneseleninic anhydride on substrates other than steroidal or triterpenoid compounds, but it seems likely that the stronger conditions required to effect oxidation with this reagent makes it less attractive than Ae two-step procedure described above. Indeed, in the few instances repotted it failed to convert hydrocinnamamitte into ciimamamide, and is said to be of no value for the dehydrogenation of acyclic esters. There are, however, several reports in which either catalytic or stoichiometric benzeneseleninic anhydride has effectively dehydrogenated cyclic ketones in high yield, a typical example being illustrated in equation (12). ... 

SCHEME 176. Oxidation of phenols with benzeneseleninic anhydride and benzeneseleninic acid... 

From a synthetic point of view, indolines are used to provide different reactivity properties from the indoles. Once a required sequence of reactions is achieved, the indoline can then be oxidized readily to the indole. One of the most effective methods for the conversion of indolines to indoles involves treatment with benzeneseleninic anhydride, together with three equivalents of a sacrificial scavenger such as indole or dihydropyran to remove the phenylselenating by-product the method has been used in the synthesis of ergot alkaloids (Equation (100)) <85TL4183, 90JCS(pi)707>. 

Barton DHR, Hui RAHF, Lester DJ, Ley SV (1979) Preparation of aldehydes and ketones by oxidation of benzylic hydrocarbons with benzeneseleninic anhydride. Tetrahedron Lett 20 3331-3334... 

Oxidation of phenols (10,23-24). The earlier report of oxidation of phenols with 1 mainly to o-quinones has been confirmed recent reports of oxidation to p-quinones has been shown to involve contamination of 1 with benzeneseleninic acid, C(,H5Se02H (2), which is para-selective for this oxidation. Solvents also can play a role. THF and benzene are the solvents of choice for 1, and CH2C12 is the best solvent for para-oxidation with 2. In acetic anhydride, both 1 and 2 are ortho-selective. In addition, phenylselenoquinones can be formed in oxidations with both 1 and 2, but this reaction can be inhibited by addition of indole. 

Pyiidineseleninic anhydride was also shown to be more reactive towards benzylic oxidation than the previously reported benzeneseleninic anhydride. This was rationalized as an effect of the greater electron-withdrawing properties of the pyridine nucleus in rendering the Se 0 bond a better enophile. Alternatively, the 2-p) ineseleninic anhydride may exist in equilibrium with a pyridinium salt which is the effective oxidant (equation 51). 

As a result of the powerful oxidizing potential of benzeneseleninic anhydride, it is incompatible with the presence of a number of functional groups, although many common moieties are well tolerated. Thus, it has been shown to convert thiocarbonyl compounds such as xanthates, thiocarbonates, thioamides and thiones, and hydrazones, oximes, thiosemicarbazones and hydroxyhttnines, into the corresponding carbonyl compounds under relatively mild conditions. Furthermore, hydrazo derivatives are converted to the azo compounds. ... 

Many reagents convert primary amines into nitriles. Some of these have been mentioned above and represent serious limitations on methods for generating carbonyl compounds. Other ways of oxidizing amines to nitriles are the use of nickel peroxide,lead tetraacetate," copper(I) chloride plus oxygen and pyridine," iodine pentafluoride and benzeneseleninic anhydride. double bromination-dehy-drobromination can be effected for the preparation of nitriles with 2 equiv. of NBS and trimethyl-amine. Likewise, fluorination and elimination of HP gives nitriles." ... 

Seleninic acids and their anhydrides, RSe(O)OH and RSe(O)OSe(O)R, are used as versatile and specific oxidizing reagents for a variety of organic compounds. In contrast with selenenic acids, seleninic acids (and their anhydrides) are stable, especially, benzeneseleninic acid, PhSe(O)OH, and benzeneseleninic anhydride, PhSe(O)OSe(O)Ph, which are commercially available. 

Zinc and acetic acid reduced the 1,4-naphthoquinone E into hydroquinone F with concomitant removal of the protective group. Ring closure of F was effected under the Mitsunobu conditions to give G. Barton s benzeneseleninic anhydride [(PhSe0)20] smoothly oxidized G to furnish (R)-ent-nocardione B (143 ) as dextrorotatory needles with orange color. Naturally occurring (—)-nocardione B (143) was therefore shown to possess (/ -configuration.35... 

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