Ketones ruthenates

Methylthiomethyl p-tolyl sulfone, 192 Potassium ruthenate, 259 Trimethylsilyl chlorochromate, 327 a-Substituted ketones (see also Halo carbonyl compounds, Hydroxy aldehydes and ketones) a-Acetoxy ketones Benzeneselenenyl chloride-Silver acetate, 27... 

Griffith, Ley et al.n discovered that, in variance with the instability and complex behaviour of perruthenate and ruthenate ions in aqueous solution, TPAP in organic media is quite stable and behaves as a very good oxidant for alcohols. Normally, it is employed in catalytic quantities in dry CH2CI2 with addition of TV-methylmorpholine /V-oxide (NMO) as the secondary oxidant. Catalytic TPAP in the presence of NMO is able to oxidize alcohols to adehydes and ketones under very mild conditions in substrates adorned by complex functionalities, and it has become one of the routine oxidants for alcohols in most Synthetic Organic Chemistry laboratories. 

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]. 

Potassium ruthenate, K2RUO4, is prepared in situ from ruthenium trichloride and aqueous persulfate. The reagent catalyzes persulfate oxidations of primary alcohols to acids, secondary to ketones, and primary amines to nitriles or acids at room temperature in high yields [196],... 

High yields of ketones result from the gentle oxidation of alcohols with compounds of ruthenium. Ruthenium tetroxide oxidizes cyclohexanol to cyclohexanone in carbon tetrachloride at room temperature in 93% yield [940], Instead of the rather expensive ruthenium tetroxide, which is required in stoichiometric amounts, catalytic amounts of ruthenium trichloride may be used in the presence of sodium hypochlorite as a reoxidant with the same results [701]. Sodium ruthenate [937] and potassium ruth-enate [196], which are prepared from ruthenium dioxide and sodium periodate in sodium hydroxide and from ruthenium trichloride and potassium persulfate, respectively, also effect oxidations to ketones at room temperature. 

Table II shows results for the electro-oxidation of secondary alcohols and ketones. In alkaline electrolyte, secondary butanol was not oxidized to methyl ethyl ketone but was cleaved to acetate. Similarly methyl ethyl ketone was cleaved to acetate, although some CO2 and propionate formed, indicative of cleavage on the other side of the carbonyl group. Butanediol (2 ) went to acetate yielding less CO2. At pH 9 in borax buffer 2 Trtanol went exclusively to methyl ethyl ketone at 89% conversion, suggesting that enolization in alkali is a necessary part of the cleavage process. Cyclohexanol and cyclohexanone were both converted to adipic acid. Figure 12 summarizes the various types of electro-organic oxidations, thus far discussed, which are observed to occur on lead ruthenate in alkaline electrolyte.

Enolization via long-range migration. An unsaturated ketone with a remote double bond uninterrupted by a quaternary carbon or heteroatom is capable of forming a Ru-enolate by heating with the title complex in benzene. Such an enolate can be trapped by aldehydes and the resulting ruthenated aldols afford 1,3-diketones through eliminated of [Ru]-H. ... 

Oxidations. By using Phl=0 (in presence of KBr) as an oxidant, alcohols are oxidized to acids and ketones in water in excellent yields. When catalyzed by either poly(4-vinylpyridine)-supported sodium ruthenate or a (salen)chromium complex chemoselective oxidation of alcohols (e.g., allylic alcohols to alkenoic acids) occurs, which is contrary to the effect of (salen)manganese and (porphyrin)iron complexes (giving epoxy alcohols). ... 

The arylation of aromatic ketones with arylboronates proceeds by an oriho-ruthenation with RuH2(CO)(PPh3)3 as the catalyst [137]. In this transformation, the final C—C bond is formed in a transmetallation-reductive elimination process. In a different reaction, ortHo-arylated compounds are obtained from o-aminoaryl ketones and arylboronates through substitution of the amino function catalyzed by the same Ru(II) complex [138], A nitrogen-directed homocouphng of aromatic compounds takes place with Ru(II) catalysts in the presence of aUylic chlorides or acetates by a mechanism that presumably involves Ru(IV) intermediates [139],... 

Chaudret and coworkers synthesized an ortho-ruthenated acetophenone complex (26) having axial tricyclohexylphosphine ligands. Complex 26 showed almost no catalytic activity, and on the basis of this observation and the activity of 22, they proposed that the binding of the CO Hgand to the ruthenium suppresses the catalytic activity of the ruthenium complex. Fogg and coworkers prepared ortho-ruthenated benzophenone complex 27, which showed only low catalytic activity and was proposed to be a catalytic sink in the alkylation of aromatic ketones. Weber and coworkers synthesized a unique zero-valent ruthenium complex (23), which was effective for the alkylation of aromatic ketones. Subsequently, Whittlesey and coworkers synthesized complex 25, which did not catalyze the hydroarylation. However, the authors stated it was highly Hkely that alternative isomers of 25 could be involved in the catalytic pathways. Further hints toward this end came with the characterization of the two N,0-coordinated acetylpyrrolyl complexes 24 and 28. Complex 24 was found to be an active catalyst of the reaction but was shown to isomerize to its inactive isomer 28 at 80 °C. 

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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