Big Chemical Encyclopedia

Chemical substances, components, reactions, process design ...

Articles Figures Tables About

Ethers oxidation with ruthenium tetroxide

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. [Pg.243]

Oxidations with ruthenium tetroxide Lactones from cyclic ethers s. lA, 221 RuOi CHa -V CO... [Pg.85]

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... [Pg.154]

Ethers in which at least one group is primary alkyl can be oxidized to the corresponding carboxylic esters in high yields with ruthenium tetroxide. Molecular oxygen with a binuclear copper (II) complex " or PdCVCuCVCO " also converts ethers to esters. Cyclic ethers give lactones. " The reaction, a special case of 19-14,... [Pg.1534]

In the acetonitrile modification reported by Sharpless and coworkers, hydrolysis t parently does not take place to any tqipreciable extent. Consequently the yield of ester can be significantly increased (equation 11). This improved procedure, along with some minor variants, therefore appears to be the method of choice for effecting the oxidation of ethers with ruthenium tetroxide, and has been widely adopted. [Pg.238]

In 1959, Henbest and Nicholls reported the conversion of the ether (1) into the corresponding lactone (2), on treatment with chromic acid in acetone at room temperature (equation 2)P Mechanistic studies on the oxidation of ethers by both ruthenium tetroxide and chromic acid were duly carried out. A more detailed analysis of the mechanistic aspects of these reagents appears in a review published by Mailer. ... [Pg.236]

Ethers in which at least one group is primary alkyl can be oxidized to the corresponding carboxylic esters in high yields with ruthenium tetroxide. Molecular... [Pg.1759]

The conversion of primary alcohols and aldehydes into carboxylic acids is generally possible with all strong oxidants. Silver(II) oxide in THF/water is particularly useful as a neutral oxidant (E.J. Corey, 1968 A). The direct conversion of primary alcohols into carboxylic esters is achieved with MnOj in the presence of hydrogen cyanide and alcohols (E.J. Corey, 1968 A,D). The remarkably smooth oxidation of ethers to esters by ruthenium tetroxide has been employed quite often (D.G. Lee, 1973). Dibutyl ether affords butyl butanoate, and tetra-hydrofuran yields butyrolactone almost quantitatively. More complex educts also give acceptable yields (M.E. Wolff, 1963). [Pg.134]

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 trioxide . 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) oxide . [Pg.985]

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. [Pg.227]

Although a number of different reagents have been discovered for the selective oxidation of ethers, e.g. halogens, iodine tris(trifluoroacetate), trichloroisocyanuric acid, UFs, A(,N-dibromobenzenesul-fonamide and lead tetraacetate, few have assumed any synthetic importance. Of these, the most significant are the metallic oxidants chromic acid and ruthenium tetroxide. DDQ has also been widely used for the oxidative d rotection of benzyl ethers. It is the aim of this chapter to review the latest developments in ether oxidation by these, and other reagents, with particular emphasis on chemo- and regio-selectivity. Several reviews on the subject have appeared previously. " The related oxidation of acetals has been reviewed recently" and will not be dealt with here. [Pg.235]

The relative reactivity of primary and secondary positions adjacent to oxygen can be strongly dependent on the nature of the oxidant. For example, treatment of the methyl ethers (8) and (10) with chromium trioxide in acetic acid leads to the formation of the formates (9) and (11), respectively (equations 13 and 14). In direct contrast, n-decyl methyl ether is oxidized exclusively to methyl n-decanoate (83% yield) by ruthenium tetroxide (equation 11). Under similar reaction conations, 3 -cholestanol methyl ether gives cholestan-3-one as the mqjor product, togedier with traces of the corresponding formate. Therefore, at least in the case of ruthenium tetroxide, primary positions appear to be more reactive than tertiary. [Pg.239]

The diols (97) from asymmetric dil droxylation are easily converted to cyclic sii e esters (98) and thence to cyclic sulfate esters (99).This two-step process, reaction of the diol (97) with thionyl chloride followed by ruthenium tetroxide catalyzed oxidation, can be done in one pot if desired and transforms the relatively unreactive diol into an epoxide mimic, ue. the 1,2-cyclic sulfate (99), which is an excellent electrophile. A survey of reactions shows that cyclic sulfates can be opened by hydride, azide, fluoride, thiocyanide, carboxylate and nitrate ions. Benzylmagnesium chloride and thie anion of dimethyl malonate can also be used to open the cyclic sulfates. Opening by a nucleophile leads to formation of an intermediate 3-sidfate aiuon (100) which is easily hydrolyzed to a -hydroxy compound (101). Conditions for cat ytic acid hydrolysis have been developed that allow for selective removal of the sulfate ester in the presence of other acid sensitive groups such as acetals, ketals and silyl ethers. [Pg.431]


See other pages where Ethers oxidation with ruthenium tetroxide is mentioned: [Pg.238]    [Pg.243]    [Pg.238]    [Pg.238]    [Pg.243]    [Pg.13]    [Pg.236]    [Pg.239]    [Pg.240]    [Pg.239]    [Pg.192]    [Pg.265]    [Pg.239]    [Pg.240]    [Pg.1526]    [Pg.739]    [Pg.1181]    [Pg.215]    [Pg.20]    [Pg.469]    [Pg.171]    [Pg.236]    [Pg.242]    [Pg.236]    [Pg.240]    [Pg.242]   
See also in sourсe #XX -- [ Pg.1534 ]




SEARCH



Ethers oxidation

Oxidation ruthenium

Ruthenium oxidation with

Ruthenium oxide

Ruthenium tetroxide

Ruthenium tetroxide oxidation

Tetroxides

© 2024 chempedia.info