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Ketones heterocyclic, oxidation

Many heterocyclic rings are made by the formation of a carbon-heteroatom bond and it is important when planning this to get the oxidation level of the carbon electrophile right. If we disconnected either C-N bond of the pyrrole 8, we get back to a ketone and an amine 9. If we disconnected the imine in imidazole 10 we should also get back to a ketone and an amine 11. Both 9 and 11 are unstable and neither is likely to be a real intermediate but the point is worth making. These carbon electrophiles are at the aldehyde or ketone oxidation level. [Pg.301]

Both exo- and endo-cyclic alicyclic and heterocyclic ketones have been reduced. Important examples are found in the preparations of cyclo-pentanol (95%), cycloheptanol (92%), /S-pyridylmethylcarbinol (85%), and l-alkyl-4-piperidinols (90%). A comparison of four reagents—sodium and alcohol, lithium aluminum hydride, hydrogen and Raney nickel, and hydrogen and copper-chromium oxide—has been made in the preparation of methyl cyclopropylcarbinol. The last method is superior for the preparation of this compound (SH)%). ... [Pg.80]

In the benzoin condensation, one molecule of aldehyde serves as an electrophile. If a carbanion is generated from protected cyanohydrins, a-aminonitriles or dithioacetals, it can react with electrophiles such as alkyl halides, strongly activated aryl halides or alkyl tosylates to form ketones. Amongst other electrophiles which are attacked by the above carbanions are heterocyclic A -oxides, carbonyl compounds, a,p-unsaturated carbonyl compounds, a,3-unsaturated nitriles, acyl halides, Mannich bases, epoxides and chlorotiimethyl derivatives of silicon, germanium and tin. [Pg.544]

Direct fluorination of aliphatics and non-C moieties Direct fluorination of benzenoid aromatics Direct fluorination of heterocyclic aromatics Oxidations of alcohols, diols and ketones with fluorine Photo-oxidation of a-terpinene and cyclopentadiene Oxidation of benzyl alcohol to benzaldehyde Homogeneously catalyzed oxidation of butyraldehyde Oxidation of sulfite to sulfate Photochlorination of aromatic isocyanates... [Pg.1065]

The first general method for mthenium(II)-catalysed oxidative dehydrogenative alkenylation of functional arenes showed successively the ability of carboxylate, heterocycle, ketone, aldehyde, amides, esters, and carbamates to behave as directing groups for C-H bond alkenylation and could also be applied to alkenes, ferrocenes, heterocycles, and protected phenols. [Pg.155]

A white solid, m.p. 178 C. Primarily of interest as a brominaling agent which will replace activated hydrogen atoms in benzylic or allylic positions, and also those on a carbon atom a to a carbonyl group. Activating influences can produce nuclear substitution in a benzene ring and certain heterocyclic compounds also used in the oxidation of secondary alcohols to ketones. [Pg.69]

The problem of the synthesis of highly substituted olefins from ketones according to this principle was solved by D.H.R. Barton. The ketones are first connected to azines by hydrazine and secondly treated with hydrogen sulfide to yield 1,3,4-thiadiazolidines. In this heterocycle the substituents of the prospective olefin are too far from each other to produce problems. Mild oxidation of the hydrazine nitrogens produces d -l,3,4-thiadiazolines. The decisive step of carbon-carbon bond formation is achieved in a thermal reaction a nitrogen molecule is cleaved off and the biradical formed recombines immediately since its two reactive centers are hold together by the sulfur atom. The thiirane (episulfide) can be finally desulfurized by phosphines or phosphites, and the desired olefin is formed. With very large substituents the 1,3,4-thiadiazolidines do not form with hydrazine. In such cases, however, direct thiadiazoline formation from thiones and diazo compounds is often possible, or a thermal reaction between alkylideneazinophosphoranes and thiones may be successful (D.H.R. Barton, 1972, 1974, 1975). [Pg.35]

The use of oximes as nucleophiles can be quite perplexing in view of the fact that nitrogen or oxygen may react. Alkylation of hydroxylamines can therefore be a very complex process which is largely dependent on the steric factors associated with the educts. Reproducible and predictable results are obtained in intramolecular reactions between oximes and electrophilic carbon atoms. Amides, halides, nitriles, and ketones have been used as electrophiles, and various heterocycles such as quinazoline N-oxide, benzodiayepines, and isoxazoles have been obtained in excellent yields under appropriate reaction conditions. [Pg.307]

In theory, three isoxazolines are capable of existence 2-isoxazoline (2), 3-isoxazoline and 4-isoxazoline. The position of the double bond may also be designated by the use of the prefix A with an appropriate numerical superscript. Of these only the 2-isoxazolines have been investigated in any detail. The preparation of the first isoxazoline, 3,5-diphenyl-2-isoxazoline, from the reaction of )3-chloro-)3-phenylpropiophenone with hydroxylamine was reported in 1895 (1895CB957). Two major syntheses of 2-isoxazolines are the cycloaddition of nitrile A-oxides to alkenes and the reaction of a,/3-unsaturated ketones with hydroxylamine. Since 2-isoxazolines are readily oxidized to isoxazoles and possess some of the unique properties of isoxazoles, they also serve as key intermediates for the synthesis of other heterocycles and natural products. [Pg.3]

In THF at -20°C the N-trimethylsilylated 2-pyrrolidinone 388 is converted by LDA into the a-anion which, on reaction with 1949 and subsequent acidification with AcOH, gives 43% 3-hydroxy-2-pyrrolidinone 1962 [150]. Lithium enolates of ketones such as camphor react with BTSP 1949 to give >95% of a mixture of exo-and mdo-2-hydroxycamphor [151]. Lithiated methyl heterocycles such as lithiated 2-methylpyridine 1963 are converted into mixtures of the 0-SiMe3 1964 and C-SiMe3 1965 compounds and C-methylated compounds such 1966 [152]. 2-Lithioto-luene 1967 is oxidized by 1949 into 1968 [140, 145] (Scheme 12.42). [Pg.286]

Dichloroethylphosphine has been shown to react with methyl vinyl ketone to form 2-ethyl-5-methyl-A -l,2-oxaphospholen-2-oxide (25), which has been converted to (26) by chlorination in the presence of base. The same phosphine adds to methyl acrylate in the presence of acetic acid to give the phosphine oxide (27). Further examples have appeared of the reactions of the phenylhydrazones of methyl ketones with phosphorus trichloride to produce the heterocycles (28). [Pg.44]

The formation of crystal inclusion of 47 and 48 with cyclic ketones of suitable ring size (cyclopentanone, cyclohexanone) and with cyclohexene oxide are also important facts. Corresponding inclusion compounds with alcohols or amines could not be obtained. With reference to the heterocyclic guest molecules, the suitability of the ring size is likely to be the decisive factor for guest inclusion. [Pg.83]

The 1,3-dipolar addition to terminal alkenes of nitrile oxides, generated from nitromethylene derivatives of bicycloheptane, provides 9,ll-ethano-13,15-isoxazolinoprostanoids, PGH analogs, with alkyl, phenyl, or additional heterocyclic fragment in the oo-chain (461). Chemical transformations of 9,11-ethano-13,15-isoxazolinoprostanoids furnish prostanoids with bifunctional fragments of P-hydroxyketone and a-aminoalcohol in the oo-chain. The reaction of P-hydroxy ketones with methanesulfonyl chloride gives rise to prostanoids with an enone component in the oo-chain. 9,ll-Ethano-16-thiaprostanoids have been prepared, for the first time, by nucleophilic addition of thiols to the polarized double bond in the oo-chain. The 1,3-dipolar addition to terminal alkenes of nitrile oxides, generated from nitromethylene derivatives of bicycloheptane provides 9,ll-ethano-13,15-isoxazolinoprostanoids with an alkyl, phenyl, or additional heterocyclic fragment in the oo-chain (462). [Pg.91]


See other pages where Ketones heterocyclic, oxidation is mentioned: [Pg.122]    [Pg.251]    [Pg.97]    [Pg.251]    [Pg.662]    [Pg.611]    [Pg.124]    [Pg.489]    [Pg.247]    [Pg.115]    [Pg.417]    [Pg.300]    [Pg.2044]    [Pg.6]    [Pg.183]    [Pg.227]    [Pg.267]    [Pg.285]    [Pg.223]    [Pg.225]    [Pg.74]    [Pg.104]    [Pg.125]    [Pg.44]    [Pg.62]    [Pg.29]    [Pg.87]    [Pg.95]    [Pg.607]   
See also in sourсe #XX -- [ Pg.124 ]




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Heterocyclic ketone

Ketones oxidant

Ketones oxidation

Oxidation heterocyclic

Oxidative heterocyclization

Oxidative ketones

Oxidative ketonization

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