Peroxides nickel

Nickel peroxide is a solid, insoluble oxidant prepared by reaction of nickel (II) salts with hypochlorite or ozone in aqueous alkaline solution. This reagent when used in nonpolar medium is similar to, but more reactive than, activated manganese dioxide in selectively oxidizing allylic or acetylenic alcohols. It also reacts rapidly with amines, phenols, hydrazones and sulfides so that selective oxidation of allylic alcohols in the presence of these functionalities may not be possible. In basic media the oxidizing power of nickel peroxide is increased and saturated primary alcohols can be oxidized directly to carboxylic acids. In the presence of ammonia at —20°, primary allylic alcohols give amides while at elevated temperatures nitriles are formed. At elevated temperatures efficient cleavage of a-glycols, a-ketols 

21-Trihydroxy-5j -pregnane-l 1,20-dione from 3a,21-Dihydroxy-5j5-preg-nane-ll,20-dione. To 3.48 g (10 mmoles) of 3a,21-dihydroxy-5i5-pregnane-11,20-dione in 100 ml of methanol is added 50 ml of 0.025 M (1.25 mmoles) methanolic cupric acetate. After 20 sec the color changes from blue to amethyst. Air is bubbled into the solution rapidly to hasten the oxidation. A sequence of further color changes ensues but after ca. 10 min the reaction mixture is blue once more. After 15 min the solution is added to 1 liter of water and the mixture is extracted twice with 200 ml of ethyl acetate. The extract is washed with dilute sodium bicarbonate and water, filtered and evaporated to dryness. 

The combined aqueous washes are acidified with dilute hydrochloric acid and extracted with ethyl acetate. Evaporation of this extract yields 86 mg of 3a-hydroxy-ll-oxo-5j -etianic acid, mp 291-293° (dec.). 

The residue from the neutral fraction is crystallized from aqueous acetone to yield 3.4 g (94%) of 3a,21,21-trihydroxy-5j -pregnane-ll,20-dione, mp 153-155°. 

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When heated in the presence of a carboxyHc acid, cinnamyl alcohol is converted to the corresponding ester. Oxidation to cinnamaldehyde is readily accompHshed under Oppenauer conditions with furfural as a hydrogen acceptor in the presence of aluminum isopropoxide (44). Cinnamic acid is produced directly with strong oxidants such as chromic acid and nickel peroxide. The use of t-butyl hydroperoxide with vanadium pentoxide catalysis offers a selective method for epoxidation of the olefinic double bond of cinnamyl alcohol (45). 

Pyridazine-3,6-diones (diazaquinones) are prepared from cyclic hydrazides by oxidation with lead tetraacetate or other oxidizing agents, such as r-butyl hypochlorite, chlorine or nickel peroxide. 

Oxidation ol alcohols to caitx>xyllc acids (or ketones) with nickel peroxide... 

A multiwavelength approach might have been considered as an alternative to chemical derivatisation. Ruddle and Wilson [62] reported UV characterisation of PE extracts of three antioxidants (Topanol OC, Ionox 330 and Binox M), all with identical UV spectra and 7max = 277 nm, after reaction with nickel peroxide in alkaline ethanolic solutions, to induce marked differentiation in different solvents and allow positive identification. Nonionic surfactants of the type R0(CH2CH20) H were determined by UV spectrophotometry after derivatisation with tetrabromophenolphthalein ethyl ester potassium salt [34]. Magill and Becker [63] have described a rapid and sensitive spectrophotometric method to quantitate the peroxides present in the surfactants sorbitan monooleate and monostearate. The method, which relies on the peroxide conversion of iodide to iodine, works also for Polysorbate 60 and other surfactants and is more accurate than a titrimetric assay. 

Isoxazolines 79, obtained from aromatic nitrile oxide cycloadditions to cyclohex-2-enone, reacted with nickel peroxide to give 3-aryl-6,7-dihydro[l] benzoisoxazol-4(5// )-ones 80. In contrast, the corresponding 2-bromocyclohex-2-enone underwent nitrile oxide cycloaddition, followed by dehydrobromination, to afford the regioisomeric 3-aryl-4,5-dihydro[l]benzoisoxazol-7(6//)-ones 81 (Scheme 1.23) (242). 

Cycloaddition of 5,6-dihydropyran-2-one with aromatic nitrile oxides leads to 3-aryl-3a,6,7,7a-tetrahydropyrano[3,4-d]isoxazol-4(47/)-ones 98. The latter react with nickel peroxide to give the corresponding dihydropyranoisoxazolones 99. Similar to 2-bromocyclohex-2-enone, 3-bromo-5,6-dihydropyran-2-one undergoes nitrile oxide cycloaddition, followed by dehydrobromination, to form regioi-someric 3-aryl-5,7-dihydropyrano 4,3-c/ isoxazol-7(4//)-ones 100 (Scheme 1.24) (242). 

The nickel hydroxide electrode resembles in its applications and selectivity the chemical oxidant nickel peroxide. The nickel hydroxide electrode is, however, cheaper, easy to use and in scale-up, and produces no second streams/ waste- and by-products [196], Nickelhydroxide electrode has been applied to the oxidation of primary alcohols to acids or aldehydes, of secondary alcohols to ketones, as well as in the selective oxidation of steroid alcohols, cleavage of vicinal diols, in the oxidation of y-ketocarboxylic acids, of primary amines to nitriles, of 2,6-di-tert-butylphenol to 2,2, 6,6 -tetra-rert-butyldiphenoquinone, of 2-(benzylideneamino)-phenols to 2-phenyloxazols, of 1,1-dialkylhydrazines to tetraalkyltetrazenes. For details the reader is referred to Ref. [195]. 

Methods for oxidative transformations continue to receive attention. Nickel peroxide on graphite oxidizes geraniol to citral in 89% yield. Three groups report " the oxidative rearrangement of tertiary vinyl carbinols. Linalool is con-... 

Treatment of carbazole with potassium permanganate in acetone (or nickel peroxide in ether ) gave mainly 9,9 -bicarbazole 9 (23%) together with the trimer 10 (8%). In the potassium permanganate oxidation,... 

Carbazole oxidized by nickel peroxide in the absence of light and in the presence of 2-methyl-2-nitrosopropane gave the radical 71, an observation taken as additional evidence for the intermediacy of radical cations, trapped in this case by the nitrosoalkane, in oxidative dimerization of carbazoles (see Section II,A,2). 

Dimerization can also be achieved using nickel peroxide " or through a photooxidation reaction. In these cases, 4-monosubstituted-5(4//)-oxazolones 293 are converted to the corresponding 4,4 -bis(oxazolones) 294 (Scheme 7.97 ... 

Some of the ring expansion reactions discussed in Section 2.03.3.3.1 can be extended to five-membered heterocycles containing two or more heteroatoms. Reaction of imidazoles and pyrazoles with dichlorocarbene, for example, gives chloropyrimidines together with small amounts of chloro-pyrazines or -pyridazines, and oxidative ring expansion of 1-aminopyrazole with nickel peroxide gives 1,2,3-triazine (this, in fact, constitutes the only known synthesis of the unsubstituted triazine). There are, however, a number of interesting and useful transformations which are unique to five-membered polyheteroatom systems. 

Synthesis of tetramethylallene via the cycloelimination reaction of 4-keto-3,3,5,5-tetramethylpyrazolinehydrazone using nickel peroxide at room temperature [132]. 

Comparison of the Nickel Hydroxide Electrode with Nickel Peroxide.125... 

For reactive and short chain alcohols the nickel hydroxide electrode and nickel peroxide exhibit the same reactivity (Table 4).,The oxidation of long chain alcohols, which is possible in good yields at the electrode has not been reported for nickel peroxide. The close similarity in yield and products indicates that in both oxidations the same reagent is effective. 

Table 4. Comparison of yields in the chemical (nickel peroxide) and anodic oxidation (nickel hydroxide electrode) of primary alcohols...

The oxidation of various secondary alcohols, including the allylic alcohols carveol (5) and P-ionol (4), leads to the corresponding ketones in 70-80 % yield (Eq. (3), Table 7). Oxidation of (—)-carveol (J) with nickel peroxide (2.5 eq., 50 °C, benzene) yielded only 33 % ketone. 

Compared to the anodic oxidation of Z-4-octene-l,8-diol (80%, Table 8) its oxidation with pyridinium dichromate in dimethyl formamide gave as the best chemical alternative only 65 % diacid Nickel peroxide oxidation under mild conditions (1.3 eq. peroxide, 25 °C, 1 M NaOH) led to 45% hydroxy acid 75, whereas under more vigorous conditions (3 eq. peroxide, 80 °C, 1 M NaOH) maleic acid was formed ... 

For the oxidation of 2,6-di-t-butylphenol (42) to diphenoquinone (45) nickel peroxide has proved to be the most suitable reagent At the nickel hydroxide electrode 42 can be oxidized in 92 % yield to 45 (Eq. (8)). For this conversion a temperature of 50-70 °C is necessary, at 25 C the oxidation is very slow. 

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