Carboxylic acids with nickel peroxide

Oxidation of alcohols to carboxylic acids (or ketones) with nickel peroxide (see 1st edition). 

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... 

Nickel peroxide, an undefined black oxide of nickel, is prepared from nickel sulfate hexahydrate by oxidation in alkaline medium with an ozone-oxygen mixture [929] or with sodium hypochlorite [930, 931, 932, 933]. Its main applications are the oxidation of aromatic side chains to carboxyls [933], of allylic and benzylic alcohols to aldehydes in organic solvents [929, 932] or to acids in aqueous alkaline solutions [929, 930, 932], and of aldehydes to acids [934, the conversion of aldehyde or ketone hydrazones into diazo compounds [935] the dehydrogenative coupling of ketones in the a positions with respect to carbonyl groups [931] and the dehydrogenation of primary amines to nitriles or azo compounds [936]. 

The unusual oxidant nickel peroxide converts aromatic aldehydes into carboxylic acids at 30-60 °C after 1.5-3 h in 58-100% yields [934. The oxidation of aldehydes to acids by pure ruthenium tetroxide results in very low yields [940. On the contrary, potassium ruthenate, prepared in situ from ruthenium trichloride and potassium persulfate in water and used in catalytic amounts, leads to a 99% yield of m-nitrobenzoic acid at room temperature after 2 h. Another oxidant, iodosobenzene in the presence of tris(triphenylphosphine)ruthenium dichloride, converts benzaldehyde into benzoic acid in 96% yield at room temperature [785]. The same reaction with a 91% yield is accomplished by treatment of benzaldehyde with osmium tetroxide as a catalyst and cumene hydroperoxide as a reoxidant [1163]. 

This is a black, hydrous mixture of higher oxides of nickel made by treating nickel sulfate in alkaline solution with sodium hypochlorite. In alkaline solution, saturated aliphatic primary alcohols of adequate water-solubility are oxidized to the carboxylic acids (30°, 3-5 hrs.). Benzyl alcohol is oxidized by the alkaline reagent to benzoic acid, but with benzene as solvent and a slight excess of nickel peroxide it is oxidized to benzaldehyde. Allylic alcohols also can be oxidized to aldehydes by this method. 

Nickel peroxide, which is readily obtainable, has proved to be a useful oxidation agent Permanganate oxidation is an effective general method for the conversion of aliphatic nitro into oxo compounds a,/3-Ethyleneketones as well as 1,4-naphthoquinones can be cheaply and safely epoxidized with hypochlorite A rapid direct preparation of peroxy acids in methanesulfonic acid has been published An efficient method for the oxidative removal of the methyl group in position 19 of steroids has been described The application of hydride transfer for carboxylations has been continued. 

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