Oxidation reactions Potassium ruthenate

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]. 

A feature of both systems is the autocatalysis by SO4 and COa (derived from the reductant) radicals. A simple rate law is observed in the Ag -catalysed oxidation of aspartic acid (Rate = A a[S208 ][Ag ][Asp] ). Medium effects are important with inhibition by ions in the order Mg + > K+ > Na+ > H+ and NOs > S04 . The uncatalysed oxidations of glyoxal and glyoxylic acid have also been investigated. Potassium ruthenate (K2RUO4), which can be readily prepared from reaction of ruthenium trichloride with aqueous persulphate, can be used cata-lytically in the presence of 8208 for the oxidation of organic substrates under mild conditions. RuO " is considered to act as a two-electron oxidant. 

Potassium ruthenate (K2RUO4) was used as a catalyst for the oxidation of benzy-lamine with K2S2O8 [109]. Primary amines can be converted to nitriles readily by aerobic oxidation reactions. James and coworkers reported that aerobic oxidative transformation of primary amines to nitriles can be carried out in the presence of a ruthenium porphyrin complex Ru(TMP)(0)2 (1) (100%) (Eq. (7.59)) [110]. 

Primary alcohols and aldehydes can also be eflBciently oxidized to acids by catalytic amounts of potassium ruthenate (K2[Ru04]) in the presence of potassium persulphate and aqueous alkali. This method is amenable to large-scale reactions, and seems especially suitable for the preparation of unsaturated and aromatic acids. 

Aromatic nitriles are now also available in good yields from aryl iodides by reaction with sodium cyanide impregnated on alumina/ from primary aralkyl-amines by oxidation with a potassium ruthenate-potassium persulphate system/ ... 

Potassium ruthenate, K2RUO4, can be used catalytically in the presence of persulphate to oxidize primary and secondary alcohols to the corresponding carboxylic acids and ketones. There is no significant reaction with tertiary alcohols, alkenes, or alkynes. The reaction proceeds at room temperature in high yield (>80%), and although catalyst turnover numbers have not been fully determined initial results suggest that they will be reasonable. 

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