Carboxylic acids with potassium ruthenate

Sodium ruthenate [957] and potassium ruthenate [196 oxidize allylic and benzylic alcohols to carboxylic acids at room temperature. Cinnamyl alcohol is transformed into cinnamic acid with sodium ruthenate in 1 M sodium hydroxide at 10 °C after 1 h in 70% yield [957]. In oxidations with potassium ruthenate, only catalytic amounts can be used in the presence of a persulfate, which reoxidizes the reduced ruthenium salt [196. ... 

Sodium ruthenate, Na2Ru04, is prepared in situ from ruthenium tetroxide (in solution in carbon tetrachloride) and 1 M sodium hydroxide by shaking for 2 h at room temperature. The reagent remains in the aqueous layer, which acquires bright-orange color [937]. It oxidizes primary alcohols to carboxylic acids and secondary alcohols to ketones and is comparable with but stronger than potassium ferrate [937]. 

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]. 

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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