Benzeneseleninic anhydride ketones

Dehydrogenation of steroidal ketones to give the a,/8-unsaturated species can be accomplished efficiently using benzeneseleninic anhydride.Ketone to enone conversion can also be attained by hydride-ion abstraction from the corresponding trialkylsilyl enol ether [equation (26)]. ... 

J-ENONES Benzeneseleninic anhydride. I LAVANONES Thallium(IU) nitrate. IIYDROARENES Manganese dioxide. INDOLES Bcn/rncsclcninic anhydride. KETONES lodylhenzcne LACTONES Benzene,soloninic anhydride. 

A number of additional methods are available. Among die most useful is the angular hydroxylation by benzeneseleninic anhydride. Oxidation of primary or secondary a-centers produces ot,p-unsaturated ketones, but where the a-center is tertiary, stereoselective hydroxylation is possible, e.g. (20). The initially formed seleno enolate undergoes 2,3-sigmatropic rearrangement and subsequent hydrolysis reveals the a-hydroxy ketone in good yield. 

Where the dienol form of an a,3-unsaturated ketone is availalde, autoxidadon giving the a -hydroxy ketone through the a -hydroperoxide is possible, as seen for saturated ketones (see Section 2.3.2.l.l.iii). Benzeneseleninic anhydride (see Section 2.3.2.l.l.iv) effects a -hydroxylation at tertiary centers, e.g. (118) to (119), again in the same manner as for saturated ketones. ... 

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). ... 

Benzylic oxidation. Barton et al have reported several examples of oxidation of benzylic hydrocarbons to aldehydes and ketones by benzeneseleninic anhydride. Phenylselenylated by-products are also obtained. 

Benzeneseleninic anhydride, C5HjSe(0)0(0)SeC5Hs, which is prepared in situ from diphenyldiselenide and tert-hniyX hydroperoxide, is used for the oxidation of alcohols to aldehydes or ketones [525]. This reagent is a suitable dehydrogenating agent for the introduction of double bonds a to carbonyl groups [526] and the regeneration of ketones from their oximes, semicarbazones, and phenylhydrazones [527]. 

The use of benzeneseleninic anhydride in the conversion of thiocarbonyl compounds into the corresponding oxo-derivatives has been reported in full similar reactions were achieved using diaryl telluroxides. ° Steroidal ketones reacted with tris(phenylseleno)borane or tris(methylseleno)borane to give phenyl or methyl selenoacetals. 

Oximes, Semicarbazones, Hydrazones, and Related Derivatives.—Lead tetraacetate was used to regenerate ketones from the semicarbazones and allowed a novel synthetic approach to 18-hydroxycorticosterone from 18-hydroxy-ll-oxoprogesterone. The use of benzeneseleninic anhydride as a deprotecting agent for phenylhydrazones, semicarbazones, oximes, and related derivatives has been described in full. ... 

Benzeneseleninic anhydride (PhSe0)20 is highly recommended for the regeneration of ketones from hydrazones, oximes, and semicarbazones. Ketones have been regenerated from the same range of derivatives using a stoicheiometric amount of titanous chloride in buffered acetic acid and dioxan. ... 

Benzeneseleninic anhydride converts hydrazones, oximes, and semicarbazones into the parent ketones, and oxidizes phenols to ortho-qmnone derivatives [e.g. (80) gives (81)]. The combination of PhSe(0)0H and H2O2 accomplishes epoxidation... 

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... 

The use of benzeneseleninic anhydride has been extended to the synthesis of aldehydes and ketones by benzylic oxidation. A similar result is obtained by the use of DDQ as oxidant. ... 

By Oxidation of Alcohols.—Barium manganate is readily available and stable, and has been recommended for the oxidation of primary and secondary alcohols to aldehydes and ketones respectively. Chromic acid adsorbed on to silica geP and the recyclable poly[vinyl(pyridinium chromate)] effect the same changes, while acid-stable primary and secondary alcohols are oxidized rapidly using potassium dichromate, sulphuric acid, methylene chloride, and a phase-transfer catalyst." Benzeneseleninic anhydride is an alternative reagent for the oxidation of alcohols under essentially neutral conditions. ... 

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