Ruthenium tetroxide preparation

The oxidation of alcohols with ruthenium tetroxide prepared by oxidation of ruthenium trichloride hydrate with sodium bromate takes place at room temperature. However, aldehydes may undergo further oxidation to carboxylic acids [940]. 

Preparation of Ruthenium Tetroxide Solution. Ruthenium dioxide (0.4 g) is suspended in 50 ml carbon tetrachloride. A solution of 3.2 g sodium metaperiodate in 50 ml water is added and the mixture stirred 1 hr at 0°. The black ruthenium dioxide gradually dissolves. 

Preparation of Ruthenium Tetroxide (/5) In a 250-ml flask equipped with a magnetic stirrer and cooled in an ice-salt bath is placed a mixture of 0.4 g of ruthenium dioxide and 50 ml of carbon tetrachloride. A solution of 3.2 g of sodium metaperiodate in 50 ml of water is added and the mixture is stirred 1 hour at 0°. The black ruthenium dioxide gradually dissolves. The clear yellow carbon tetrachloride layer is separated and filtered through glass wool to remove insoluble materials. The solution may be used immediately or stored in the cold in the presence of 50 ml of sodium metaperiodate solution (1 g/50 ml). As prepared above, the solution is about 0.037 M in ruthenium tetroxide and contains 0.3 g/50 ml. 

The sequence has been applied to the synthesis of 1,4-cyclohexanedione from hydroquinone 10), using W-7 Raney nickel as prepared by Billica and Adkins 6), except that the catalyst was stored under water. The use of water as solvent permitted, after hltration of the catalyst, direct oxidation of the reaction mixture with ruthenium trichloride and sodium hypochlorite via ruthenium tetroxide 78). Hydroquinone can be reduced to the diol over /o Rh-on-C at ambient conditions quantitatively (20). 

From the reaction of 5-0-benzoyl-l,2-0-isopropylidene-o -D-en/t/iro-pentofuranos-3-ulose (prepared in 80% yield by oxidation of 5-0-benzoyl-l,2-0-isopropylidene- -D-xylofuranose (35,36) with ruthenium tetroxide) with an excess of diazomethane in methanol-ether, two main products (m.p. 44°-45°C. and 76°-77°C.), both epoxides, could be isolated by chromatography of the product on a silica column. An... 

If a mixture of diphenyl sulphide and the corresponding sulphoxide are treated with osmium tetroxide in boiling ether for 48 hours the sulphide is unchanged whilst the sulphoxide is converted into the sulphone in 96% yield with concomitant production of osmium trioxide140. It thus seems that this method would be useful synthetically for the preparation of sulphones from sulphoxides containing sulphide functionalities. Ruthenium tetroxide may be used in place of osmium(VIII) oxide148. 

A novel oxidation of sulphilimines using ruthenium tetroxide (generated in situ from ruthenium dioxide in a two-phase system) for the preparation of sulphoximines has been reported and proceeds in yields greater than 85%185. 

Hydroxy-5-oxo-3,5-seco-4-norandrostane-3-carboxylic acid has been prepared by ozonolysis of testosterone2-4 or of testosterone acetate, followed by alkaline hydrolysis,5 and by the oxidation of testosterone acetate with ruthenium tetroxide.9... 

Another approach to (R)-(-)-phoracantholide I (245) used a ring enlargement of cyclohexanone (255) which had been alkylated with chiral synthon 256 (Scheme 14) [206]. Thus, compound 257 was prepared in 35% yield on a 7-g scale by alkylation of cyclohexanone with chiral 256. Cyclization with Am-berlyst A-15 provided enol ether 258 that was directly submitted to ruthenium tetroxide oxidation to give oxolactone 259 in a 47% yield. Reduction of the latter with catecholborane via its tosylhydrazone afforded (R)-(-)-phoracan-tholide I (245) in 31% yield. 

Mention may be made, finally, of an unsuccessful attempt, recently described by Berkowitz and Bylander,141 to prepare the still unknown substance glycollic lactone by ruthenium tetroxide oxidation of ethylene oxide in carbon tetrachloride at 0°. Tarry products were obtained, which could have been Canned by ruthenium dioxide-oatalyred polymerisation f thiB highly strained a-lactone. 

The use of cyclic sulfates in synthetic applications has been limited in the past because, although cyclic sulfites are easily prepared from diols, a convenient method for oxidation of the cyclic sulfites to cyclic sulfates had not been developed. The experiments of Denmark [70] and of Lowe and co-workers [71 ] with stoichiometric ruthenium tetroxide oxidations and of Brandes and Katzenellenbogen [72a] and Gao and Sharpless [68] with catalytic ruthenium tetroxide and sodium periodate as cooxidant have led to an efficient method for this oxidation step. Examples of the conversion of several diols (67) to cyclic sulfites (68) followed by oxidation to cyclic sulfates (69) are listed in Table 6D.7. The cyclic sulfite/cyclic sulfate sequence has been applied to 1,2-, 1,3-, and 1,4-diols with equal success. Cyclic sulfates, like epoxides, are excellent electrophiles and, as a consequence of their stereoelectronic makeup, are less susceptible to the elimination reactions that usually accompany attack by nucleophiles at a secondary carbon. With the development of convenient methods for their syntheses, the reactions of cyclic sulfates have been explored, Most of the reactions have been nucleophilic displacements with opening of the cyclic sulfate ring. The variety of nucleophiles used in this way is already extensive and includes H [68], [68,73-76], F" [68,72,74], PhCOCT [68,73,74], NOJ [68], SCN [68],... 

Pseudo-cc-DL-allopyranose (61) has been prepared from 54 by epimerization of the C-3 configuration as follows. O-Isopropylidenation of 54 with 2,2-dimethoxypropane gave l,2 4,6-di-0-isopropylidene-pseudo-a-DL-glucopyranose (56). On oxidation with ruthenium tetroxide and sodium metaperiodate, 56 gave the 3-oxo derivative (57), which was converted into l,2 4,6-di-0-isopropylidene-pseudo-a-DL-allopyranose (58) exclusively by catalytic hydrogenation under the presence of Raney nickel. Conven-. tional acetylation of 58 furnished the 3-O-acetyl derivative (59). Hydrolysis of 59 with aqueous acetic acid, followed by acetylation afforded pseudo-a-DL-allopyranose pentaacetate (60), which gave the free pseudo-sugar 61 on usual alkaline hydrolysis [22] (Scheme 13). 

Increased reactivity toward nucleophiles may render the five-membered cyclic sulfates unstable, for instance, because of an intramolecular nucleophilic attack <1997J(P1)3173>. Thus, when the sulfate 44 is prepared by oxidation of the corresponding sulfite with ruthenium tetroxide, it undergoes a clean rearrangement at room temperature to the isomeric six-membered cyclic sulfate of 2-benzoyloxypropane-l,3-diol (Scheme 5) <1997J(P1)3173>. 

A convenient method of preparing a fairly pure specimen of potassium chlor-ruthenite consists in adding freshly distilled ruthenium tetroxide to concentrated hydrochloric acid and digesting on the water-bath until evolution of chlorine ceases. This requires about two days. 

Ruthenium tetroxide dissolves to a slight extent in water. It is also soluble in caustic alkali, from which solutions a black precipitate of finely divided ruthenium is obtained on addition of alcohol.2 Both the aqueous solution and the pure substance itself possess an odour resembling that of ozone. Its vapour, however, is not poisonous like that of the corresponding tetroxide of osmium. In contact with alcohol the solid tetroxide is reduced with explosive violence.3-4 When covered with water, to which a concentrated solution of caesium chloride is subsequently added and a little hydrochloric acid, ruthenium tetroxide is gradually converted into the oxy-salt, Cs2Ru02CI4. The corresponding rubidium salt has likewise been prepared.3... 

Methyl />-tolyl sulfone has been prepared by oxidation of methyl 7>-tolyl sulfide with hydrogen peroxide 4 r or ruthenium tetroxide,6 by alkylation of sodium -toluenesullinate with methyl iodide 7,8 or with methyl potassium sulfate,9 by decarboxylation of -tolylsulfonylacetic acid,7 by thermal decomposition of tetramethylammonium -toluenesulfinate,10 by reaction of cw-bis-(%tolylsulfonvl)-ethene with sodium hydroxide (low yield),11 by the reaction of methanesulfonyl chloride with toluene in the presence of aluminum chloride (mixture of isomers),12 by... 

Trithioles and 1,3,2-dioxathiolanes. 1,2,3-Trithiolanes are prepared by reaction of alkenes with elemental sulfur . The synthesis of 1,3,2-dioxathiolane -oxides (cyclic sulfites) and 1,3,2-dioxathiolane S, -dioxides (cyclic sulfates) is discussed in comprehensive reviews <1997AHC(68)89, 2000T7051>. The most widely used method for the preparation of 1,3,2-dioxathiolane A-oxides 557 is the reaction of the corresponding 1,2-diols 556 with thionyl chloride in the presence of pyridine or triethylamine (Scheme 251). More reactive 1,3,2-dioxathiolane S,A-dioxides 558 are usually obtained by oxidation of sulfites 557 with sodium periodate, which is mediated by ruthenium tetroxide generated in situ from a catalytic amount of ruthenium trichloride <1997AHC89, 2000T7051, CHEC-III(6.05.10.3)183>. 

The physical properties, preparation and reactions of ruthenium tetroxide have been reviewed by Lee and van den Engh, Rylander," Haines and Hetuy and Lange. A more vigorous oxidant than osmium tetroxide, its reaction with double bonds produces only cleavage products. " Under neutral conditions aldehydes are formed from unsaturated secondary carbons while carboxylic acids are obtained under alkaline or acidic conditions. For example, Shalon and Elliott" found that ruthenium tetroxide reacted with compound (11) to give the corresponding aldehyde under neutral conditions, but that a carboxylic acid was formed in acidic or alkaline solvents (equation 23). 

When used in stoichiometric amounts, ruthenium tetroxide is usually prepared by oxidation of hydrated mthenium dioxide or trichloride with aqueous periodate or hypochlorite and then extracted into carbon tetrachloride. However, since ruthenium compounds are expensive it is more common to use only catalytic amounts of RUO2-2H2O or RuCb H20 in the presence of a cooxidant that continuously regenerates ruthenium tetroxide. 

The investigation of potential perfumery compounds from manool has continued with the preparation of some 12-methylene derivatives [e.g. (30)]. A relatively stable ozonide (31) has been obtained from manool. The crystal structure of the ruthenium tetroxide oxidation product (32) obtained from manool has been determined. The sulphur derivatives of the perfumery acetals obtained from manool have been prepared. ... 

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