Benzeneseleninic anhydride oxidation

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. 

Benzeneseleninic anhydride oxidizes hydrazines to azo-compounds and hydrazones to acylazo-compounds. Azo-compounds have also been synthesized by photolysis of iminophosphoranes, reaction of hydrazones with allyl acetate under nickel catalysis/ reaction of A/-methyl-N-tosylhydrazones with amines/ and deoxygenation of azoxy-compounds/ ... 

P-Azo-[2-methyl-1,2-dicarbadecaborane( 14)], 2624 2-Azoxyanisole, 3653 1,4-Benzenediol-oxygen complex, 2334 Benzeneperoxy sulfonic acid, 2341 Benzeneseleninic acid, 2335 Benzeneseleninic anhydride, 3495 Benzenethiol, 2344 2,2 -Bi-l,3-dithiole, 2215 2,2 -Bipyridyl 1-oxide, 3258 Bis(cyclopentadienyl)lead, 3294 Bis-A(imidosulfurdiiluoridato)mercury, 4342 Bismuth trisulfide, 0234... 

Among other oxidizing agents286 that have been used to accomplish the conversion of ArCHj to ArCHO are ceric ammonium nitrate,287 ceric trifluoroacetate,288 benzeneseleninic anhydride,257 KMnCV-EtjN,289 and silver(II) oxide.290 Oxidation of ArCHj to carboxylic acids is considered at 9 11. 

Oxidation of phenols and hydroquinones.3 Both 1- and 2-naphthol are oxidized by benzeneseleninic anhydride to 1,2-naphthoquinone in comparable yield (62-63%). This orr/io-selectivity is general and is explained by a mechanism outlined in equation (I). As expected, the reagent oxidizes hydroquinones to the quinones in 84-92% yield. 

Benzeneselenenyl halides, 34-37 Benzeneselenenyl iodide, 36 Benzeneseleninic anhydride, 37—39 Benzenesulfenyl chloride, 39-40 Benzenesulfonyl fluoride, 40 Benzenesulfonylnitrile oxide, 40-41 1 -Benzenesulfonyl-2-trimethylsilylethane, 41-42... 

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... 

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." ... 

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. 

Baeyer-Villiger oxidation, 56, 196, 324, 509 Barium manganate, 23 Barium oxide, 23 Beckmann rearrangement, 472 Benzal chlorides, 465 Benzeneboionic acid, 23-24 7) -Benzenechiomium tricarbonyl, 117 Benzeneselenenic acid, 24 Benzeneselenenic anhydride, 2S Benzeneselenenyl bromide, 25-32 Benzeneselenenyl chloride, 25-32 Benzeneseleninic acid, 32 Benzeneseleninic anhydride, 32-34 Benzeneselenocyanate-Copper(II) chloride, 34-35... 

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 oxidation of alcohols to aldehydes can also be accomplished by benzeneseleninic anhydride, (0 115860)20, either as such [525] or prepared in situ from diphenyldiselenide, (0 115)2862, and rert-butyl hydroperoxide [1140]. Benzylic alcohols are oxidized more rapidly than allylic... 

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