Ruthenium tetroxide, oxidation

Oxidation of a mixture of perfluorononene isomers to a mixture of per-fluorocarboxylic acids is accomplished with two agents, potassium permanganate and ruthenium tetroxide. Oxidation with potassium permanganate is slower and gives lower yields than oxidation with ruthenium tetroxide [40] (equation 32). 

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. 

Methods for the Synthesis of a-Methylene Lactones P. A. Grieco, Synthesis, 1975, 67-82. Ruthenium Tetroxide Oxidations J. L. Courtney and K. F. Swansborough, Rev. Pure Appl. Chem., 1972, 22, 47-54. 

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],... 

Cyclic sulfites (68) also are opened by nucleophiles, although they are less reactive than cyclic sulfates and require higher reaction temperatures for the opening reaction. Cyclic sulfite 77, in which the hydroxamic ester is too labile to withstand ruthenium tetroxide oxidation of the sulfite, is opened to 78 in 76% yield by reaction with lithium azide in hot DMF [82], Cyclic sulfite 79 is opened with nucleophiles such as azide ion [83] or bromide ion [84], by using elevated temperatures in polar aprotic solvents. Structures such as 80 generally are not isolated but as in the case of 80 are carried on (when X = N3) to amino alcohols [83] or (when X = Br) to maleates [84] by reduction. Yields are good and for compounds unaffected by the harsher conditions needed to achieve the displacement reaction, use of the cyclic sulfite eliminates the added step of oxidation to the sulfate. 

The synthesis of telechelic oligomers by oxidative cleavage has been extensively studied by numerous authors and Cheradame [117] reviewed the main reactions leading to telechelic polymers starting from high molecular polymers. As he showed, ozonolysis remains one of the preferred method in addition to Ruthenium tetroxide oxidation to obtain a-co functional oligomers. 

Ruthenium tetroxide oxidizes an alcohol to furnish an aldehyde. However, the oxidation does not stop at this stage. As soon as the corresponding aldehyde hydrate has been formed from the aldehyde at equilibrium—which is ensured by the high water content in the reaction mixture—the oxidation continues to form the carboxylic acid (example Figure 17.12). Mecha-... 

H2-labelled thioridazine 56 (the phenothiazine-type antipsychotic agent) has been obtained recently39 for metabolic and pharmacokinetic studies by a new route (equation 16) from 2-(2-hydroxyethyl)piperidine 57. The key steps in this sequence of reactions involve ruthenium tetroxide oxidation of the 7V,0-diacetylated starting material 58 and subsequent lithium aluminium deuteride reduction of the 2-(2-acetoxyethyl)-6-piper-idinone (59, R = Ac). Treatment of 60 with thionyl chloride produced 2-(2-chloroethyl)-l-methyl[6,6-2H2]piperidine which, on N(10)-alkylation of 2-methylthio-10i/-phenothia-zine, yielded 56. For each of the seven steps in the conversion of 57 to 56 the yield has been at least 76%40. 

Secondary positions tend to be more reactive towards oxidation than tertiary positions, unless steric hindrance (Uctates otherwise. Good examples of this are the chromic acid oxidation of the ether (12)4 and the ruthenium tetroxide oxidation of the ether (13), both of which lead to lactone formation (Scheme 2). Oxidation of the quassinoid intermediate (14), on the other hand, is completely nonselective (equation 15). ... 

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. ... 

Where functional groups are present which are more readily oxidized than the ether group, multiple reactions can occur. For example, in their total synthesis of (-i-)-tutin and (-i-)-asteromurin A, Yamada et al. observed concomitant oxidation of a secondary alcohol function in the oxidation of the ether (30) with ruthenium tetroxide (equation 24). The same group successfully achieved the simultaneous oxidation of both ether functions of the intermediate (31) in their related stereocontrolled syntheses of (-)-picrotox-inin and (-i-)-coriomyrtin (equation 25). Treatment of karahana ether (32) with excess ruthenium tetroxide resulted in the formation of the ketonic lactone (33) via oxidation of both the methylene group adjacent to the ether function and the exocyclic alkenic group (equation 26). In contrast, ruthenium tetroxide oxidation of the steroidal tetral drofuran (34) gave as a major product the lactone (35) in which the alkenic bond had been epoxidized. A small amount of the 5,6-deoxylactone (17%) was also isolated (equation 27). This transformation formed the basis of a facile introduction of the ecdysone side chain into C-20 keto steroids. 

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. 

The oxidation products of mixed ethers may differ when different oxidants are used. Whereas ruthenium tetroxide oxidizes benzyl methyl... 

I friadate-ruthenium tetroxide oxidation. This reaction, attributed to Pappo and leeker, is illustrated by a procedure of Stork et al. for effecting the oxidative... 

Apart from an alkaline hydrolysis affecting mainly ester and amide bonds a boron tribromide treatment and a ruthenium tetroxide oxidation were applied to the extracted residues. The BBr3-treatment cleaves aromatic and aliphatic ether and ester bonds. The oxidation using RuCU attacks the aromatic carbon atoms and releases, therefore, mainly unalterated aliphatic moieties. 

Fig. 7 Molecular structures of selected anthropogenic compounds released by ruthenium tetroxide oxidation...

The ruthenium tetroxide oxidation of 3-oxoperhydropyrrolo[l,2-c]oxazole (225) gave the 7a-hydroxyl derivative (226) in high yield (Equation (26)) <85CPB5042>. 

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