Ruthenium tetraoxide, oxidation

Epimerization of 50 at C-3 furnished carba-a-DL-allopyranose (60). Stepwise, 0-isopropylidenation of 50 with 2,2-dimethoxypropane afforded compound 56. Ruthenium tetraoxide oxidation of 56 gave the 3-oxo derivative 57, and catalytic hydrogenation over Raney nickel converted 57 into the 3-epimer 58 exclusively. Hydrolysis of 58, and acetylation, provided the pentaacetate 59, which was converted into 60 on hydrolysis. ... 

The optimized ruthenium tetraoxide oxidation conditions reported by Sharpless and co-workers44 gave a significantly higher and consistent... 

C. Oxidation with Ruthenium Tetraoxide and Chromate Based... 

Unlike palladium(II), osmium tetraoxide and ruthenium tetraoxide catalyze the dihydroxylation of one or both double bonds of an allene. The osmium tetraoxide-catalyzed dihydroxylation of unsymmetrically substituted allenes 45 can lead to two different a-ketols, 46 and 47, depending on which of the double bonds is oxidized. David et al. studied this reaction using NMO as a stoichiometric oxidant and found good product selectivity in a few cases, but the yields were only moderate (Scheme 17.15) [16]. They showed that the most substituted double bond was oxidized preferably when the bulkiness of the allene substituents did not interfere. 

P. E. Morris, D. E. Kiely, Ruthenium Tetraoxide Phase-Transfer-Promoted Oxidation of Secondary alcohols to Ketones, J. Org. Chem. 52 (1987) 1149-1152. 

Synthesis of D-apiose from 1,2-O-isopropylidene- -L-threofuranose (28) has been accomplished.128 Oxidation with ruthenium tetraoxide... 

Uronic acid degradation of the fully methylated Klebsiella type 47 capsular polysaccharide120 results in a partially methylated polysaccharide having a disaccharide repeating-unit (see Section IV,2, p. 218), in which the hydroxyl groups at C-3 in the L-rhamnose residues are free. Oxidation with ruthenium tetraoxide consequently gave the product 82, which, on treatment with base, followed by... 

Isopropylidene-/ -D-fhra>-pentofuranosyl-2-ulose)adenine (22) was obtained38 from 9-(3,5-0-isopropylidene-/ -D-xylofuranosyl) adenine (21) by oxidation with ruthenium tetraoxide.37... 

In contrast to those results, no useful discrimination between endo and exo hydroxyl groups could be found when employing ruthenium tetraoxide as an oxidant.213 Compounds 4,3, and 5 each affords the diketone 9 exclusively this was isolated as the bis(2,4-dinitrophenylhydrazone). 

Oxidation of l,2 5,6-di-0-isopropylidene-a-D-glucofuranose (217) with ruthenium tetraoxide, using a phase-transfer catalyst, gave the 3-ulose derivative 218, which by further hydrolysis afforded D-n Zw-hexos-3-ulose 219. Benzyltriethylammonium chloride (BTEAC) was used as the catalyst. Using the same oxidant and conveniently derivatized starting materials, a-D-xy/o-hexofuranos-5-ulose, a-D-n Zw-hexofuranos-5-ulose, and /f-L-arabino-hexofuranos-5-ulose derivatives were obtained.436... 

Ruthenium tetraoxide is a powerful oxidant it is more reactive than osmium tetraoxide, and combines explosively with ether or benzene, so that it is generally used as a dilute solution in carbon tetrachloride. Beynon et al.155 first demonstrated the usefulness of this reagent in carbohydrate chemistry by converting methyl 4,6-0-benzylidene-2-deoxy-a-D-n bo- and -D-uraZu rao-hexopyranosides into methyl 4,6-0-benzylidene-2-deoxy-a-D-eryt/zro-hexopyranosid-3-ulose. 

The use of ruthenium tetraoxide as an oxidant in organic chemistry has been reviewed161 and several applications to the carbohydrate field have been described (Ref. 1, p. 1147). 

Oxidation of organic compounds by ruthenium tetraoxide has been reviewed. The oxidation of various types of organic compounds such as alkanes, alkenes, allenes, aromatic rings, alcohols, amines, and sulfides has been discussed The cyclic oxoruthe-nium(VI) diesters that are formed in the initial step of the oxidation of alkenes are considered to be intermediates in the formation of 1,2-diols.70 The development of new and selective oxidative transformations under ruthenium tetroxide catalysis during the past 10 years has been reviewed. The state of research in this field is summarized and a systematic overview of the reactivity and the reaction mode of ruthenium tetroxide is given.71... 

For the ruthenium tetraoxide-catalysed oxidation of propan-l-ol by diperiodato-cuprate(III), hexacyanoferrate(III), periodate, and chloramine-T, a mechanism of direct reaction between Ru(VIII) and propan-l-ol in a slow step to give propanal and Ru(VI) followed by a fast oxidation of Ru(VI) to Ru(VIII) by the co-oxidant has been proposed.73... 

Initially, the oxidation conditions chosen for 154 to 157 were the modified ruthenium tetraoxide conditions of Sharpless and co-workers.44 The crude oxidation products were converted to methyl esters 106,160, 161, and 162 and their C-2 epimers 163 to 166 using either diazomethane or trimethylsilyldiazomethane.77 The epimer ratios were determined from integration of the H NMR spectra of the crude esterification products to ensure that accurate ratios were obtained without losing minor isomers during chromatography. The results obtained are summarized in Scheme 60 and Table 15. 

A variety of other oxidation conditions were investigated overall, the ruthenium tetraoxide method gave the most consistent results and, importantly, required the least purification. The results obtained are summarized in Table 16. 

The oxidation catalyst is believed to be ruthenium tetraoxide based on work by Engle,149 who showed that alkenes could be cleaved with stoichiometric amounts of ruthenium tetraoxide. Suitable solvents for the Ru/peracid systems are water and hexane, the alkene (if liquid) and aromatic compounds. Complex-ing solvents like dimethylformamide, acetonitrile and ethers, and the addition of nitrogen-complexing agents decrease the catalytic system s activity. It has also been found that the system has to be carefully buffered otherwise the yield of the resulting carboxylic acid drops drastically.150 The influence of various ruthenium compounds has also been studied, and generally most simple and complex ruthenium salts are active. The two exceptions are Ru-red and Ru-metal, which are both inferior to the others. Ruthenium to olefin molar ratios as low as 1/20000 will afford excellent cleavage yields (> 70%). vic-Diols are also... 

Carlsen PHJ, Katsuki T, Martin VS, Sharpless KB (1981) A Greatly Improved Procedure for Ruthenium Tetraoxide Catalyzed Oxidations of Organic Compounds. J Org Chem 46 3936... 

Overend and coworkers have employed ruthenium tetraoxide in carbon tetrachloride for the oxidation of single hydroxyl groups in acetals of methyl glycosides. Similar oxidations may be performed in the presence of sulfonic ester groups, the oxidant being continuously regenerated with potassium metaperiodate. 

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