Big Chemical Encyclopedia

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

Articles Figures Tables About

Molybdenum peroxide

DMSO, molybdenum peroxide, benzene, reflux, 7-20 h, 60% yield. This method was used to m onoprotect 1,2-diols. The method is not general because oxidation to a-hydroxy ketones and diketones occurs with some substrates. On the basis of the mechanism and the results it would app>ear that overoxidation has a strong conformational dependence. [Pg.21]

Another approach to an oxidative desulphonylation reaction is to oxidize an a-sulphonyl carbanion with an oxidizing agent that is also nucleofugal. An example of this was presented by Little and Sun Ok Myong203 who used a molybdenum peroxide complex (M0O5.Pyridine.HMPA) as the oxidant. However, this reagent is expensive and... [Pg.961]

Ketones and carboxylic esters can be a hydroxylated by treatment of their enolate forms (prepared by adding the ketone or ester to LDA) with a molybdenum peroxide reagent (MoOs-pyridine-HMPA) in THF-hexane at -70°C. The enolate forms of amides and estersand the enamine derivatives of ketones can similarly be converted to their a hydroxy derivatives by reaction with molecular oxygen. The M0O5 method can also be applied to certain nitriles. Ketones have also been Qc hydroxylated by treating the corresponding silyl enol ethers with /n-chloroperoxy-... [Pg.915]

Molybdenum peroxide immobilized by coordination of a chelating polymer Diaion CR-20. [Pg.434]

Other methods for a-hydroxy ketone synthesis are addition of O2 to an enolate followed by reduction of the a-hydroperoxy ketone using triethyl phosphite 9 the molybdenum peroxide-pyridine-HMPA oxidation of enolates 10 photooxygenation of enol ethers followed by triphenylphosphine reduction 11 the epoxidation of trimethyl silyl enol ethers by peracid 1 - the oxidation of trimethylsilyl enol ethers by osmium tetroxide in N-methylmorpholine N-... [Pg.142]

Direct conversions of sulfones to carbonyl compounds have been realized by oxidative desulfonation of the a-carbanions. Molybdenum peroxide (Mo05-Py-HMPA) [266], or bis(trimethylsilyl)peroxide (Mc3SiOOSiMej, BTSP, Table 3.3) [267] were used as oxidants. Hwu s method with BTSP is attractive and was found useful for the preparation of 180-Iahelled compounds [267] in this one-pot reaction Me3SiO behaves as a leaving group and a back-attacking species. [Pg.42]

Enolates may be converted directly into a-hydroxy-ketones by reaction with the molybdenum peroxide complex MoOs,py,HMPA. The 17-ketone (188), transformed into its enolate with lithium di-isopropylamide at —70°C, gives the 16a-hydroxy-17-ketone (189) in 75% yield.172 Carbonyl transposition to the vicinal position can be effected in high yield by a new five-step process.173 A 17-oxo-steroid (188) was transformed into the 16-ketone (193) via the phenylthioketone (190) and the 16-phenylthio-16-ene (192) by the route illustrated in Scheme 5. [Pg.252]

In addition to molecular oxygen, a number of reagents have been developed for introduction of oxygen into a caibon-4ithium or carbon-magnesium bond. These include peroxides, molybdenum peroxide-pyridine-hexamethylphosi ioramide (MoOPH), sulfonyloxaziridines, nitrobenzene" and oxidation of the boronate" after transmetallation. [Pg.330]

Alkylation or allylation reactions of a-metalloalkyl sulfones followed by oxidation of the caibon center bearing the sulfonyl group (Bu"Li and dimethyl disulfide, or a three-fold excess of molybdenum peroxide or a slight excess of bis(trimethylsilyl) peroxide, BTSP ) have led to novel routes to... [Pg.160]

A convenient synthetic method for the conversion of aryl bromides to phenols is the reaction of the corresponding organometalUc reagents with molybdenum peroxide-pyridine-hexamethylphosphoramide (MoOs-Py-HMPA = MoOPH)". This method provides a mild one-pot reaction sequence for the synthesis of phenols under basic conditions. Phenols are obtained in good to excellent yields with several prototype compounds. Other strongly basic carbanions have been hydroxylated with MoOPH, including aryllithium derivatives" . Table 2 shows some examples of this type of reaction" . ... [Pg.416]

MoOPH [pronounced moof and more correctly oxidoperoxymolybdenum(aqua)-(hexa-methylphosphoric triamide)] is a molybdenum peroxide complex 245 that hydroxylates lithium enolates.39... [Pg.800]

CCRIS 1163 EINECS 215-204-7 HSDB 1661 Mo-12021 Molybdena Molybdenum oxide Molybdenum peroxide Molybdenum trioxide Molybdenum(VI) oxide Molybdenumperoxide ... [Pg.421]

Enolate hydroxylation is a problem of long standing. Direct oxygenation succeeds with the fully substituted enolates of certain o,a-disubstituted ketones and a variety of carboxylic acid derivatives (ester anions, acid dianions, amide anions), but the reaction of enolates, RCH = C(0")R or CH2 = C(0")R, with oxygen results in complex products of overoxidation. The stable molybdenum peroxide reagent MoOj Py-HMPA (MoOPH), first prepared by Mimoun, allows the conversion of RCH = C(0Li)R into RCH(0H)C0R in generally good yields (Table I). In some cases, the a-diketone is formed as a byproduct. [Pg.67]

Molybdenum peroxide oxidizes enolates to a-hydroxyketones both ketone and ester enolates can be oxidized/ This reagent is prepared by dissolving... [Pg.383]

Lithium diisopropylamide s. under Molybdenum peroxide complex i-Pr2NLi... [Pg.47]

Molybdenum peroxide complex j lithium bis (trimethylsilyl) amide <-... [Pg.40]

Anionic molybdenum peroxide complex Sulfoxides and sulfones from thioethers... [Pg.318]

See other pages where Molybdenum peroxide is mentioned: [Pg.655]    [Pg.970]    [Pg.655]    [Pg.970]    [Pg.428]    [Pg.727]    [Pg.428]    [Pg.434]    [Pg.132]    [Pg.699]    [Pg.302]    [Pg.486]    [Pg.1752]    [Pg.140]    [Pg.189]    [Pg.1006]    [Pg.207]    [Pg.25]    [Pg.72]    [Pg.396]    [Pg.292]    [Pg.366]    [Pg.243]    [Pg.313]   
See also in sourсe #XX -- [ Pg.699 ]

See also in sourсe #XX -- [ Pg.597 ]



SEARCH



© 2024 chempedia.info