Search

The oxidative esterification of 4,4′-Biphenyldicarboxaldehyde with hexafluoroisopropanol is reported. The methodology, making a novel hexafluoroisopropyl ester uses a green, recyclable oxoammonium salt along with easily obtained sodium persulfate. [ABSTRACT FROM AUTHOR]

The oxidative esterification of 4,4′-Biphenyldicarboxaldehyde with hexafluoroisopropanol is reported. The methodology, making a novel hexafluoroisopropyl ester uses a green, recyclable oxoammonium salt along with easily obtained sodium persulfate.

Comprehensive Summary: As one of the most common structural motifs in natural products, cyclopentenones usually can be fabricated by Nazarov cyclization using divinyl ketones or functionalized tertiary divinyl carbinols (TDCs) as substrates. However, straightforward method for transforming unfunctionalized TDCs to their corresponding cyclopentenones is currently lacking. Herein, we wish to report the total syntheses of four structurally distinct terpenoids, namely laurane‐type marine sesquiterpenoids isolaurene, debromoaplysin and aplysin, and guaiane sesquiterpenoid guaiadienone A, all using a novel synthetic method, named oxidative Nazarov cyclization, as the key step. This work demonstrated our robust method is suitable for synthesizing various highly substituted cyclopentenones. [ABSTRACT FROM AUTHOR]

Oxoammonium salts have demonstrated superior efficacy as reagents in mediating various reactions involving tertiary alcohols, including the eliminative functionalization of tertiary benzylic alcohols, oxidative rearrangement of tertiary allylic alcohols, and oxidative Nazarov cyclization. These reactions have been believed to be triggered by the addition of alcohols to the N−O double bonds of oxoammonium cations. However, in this work, a combination of density functional theory (DFT) and ab initio molecular dynamics (AIMD) calculations shows that the formation of this adduct is thermodynamically unfavorable. A thorough exploration of the possible mechanisms has shown that the reaction occurs through the ring opening of the oxoammonium cation. The oxoammonium cation acted as a masked tertiary carbocation and triggered the subsequent reactions. The computational results were further supported by control experiments and high‐resolution mass spectroscopy (HRMS) characterization. [ABSTRACT FROM AUTHOR]

Novel acyl pyrazoles and acyl triazoles have been prepared by means of the oxidative amidation of aldehydes in the presence of the requisite azole. Yields range from modest to good in both cases, and some limitations of the substrate scope have been discovered. Acyl pyrazoles were prepared by treatment of a mixture of aldehyde and pyrazole with an oxoammonium salt bearing the nitrate anion. In the case of acyl triazoles, the oxidative functionalization was performed using sodium persulfate as a terminal oxidant in the presence of a catalytic quantity of a nitroxide.

The acyl pyrazole derivative (3,5-di-tert-butylphenyl)(1H-pyrazol-1-yl)methanone was prepared simply and rapidly in 86% isolated yield by means of an oxidative functionalization reaction of an aldehyde with pyrazole. A substoichiometric quantity of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium nitrate was used as the oxidant. The reaction was performed solvent-free and in the absence of a base, making it a clean, green approach. The mixture of aldehyde, pyrazole, and the oxidant was heated at 55 °C for 3 h, and then, the product was isolated in analytically pure form via extraction with no need for column chromatography. [ABSTRACT FROM AUTHOR]

The acyl pyrazole derivative (3,5-di-tert-butylphenyl)(1H-pyrazol-1-yl)methanone was prepared simply and rapidly in 86% isolated yield by means of an oxidative functionalization reaction of an aldehyde with pyrazole. A substoichiometric quantity of 4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium nitrate was used as the oxidant. The reaction was performed solvent-free and in the absence of a base, making it a clean, green approach. The mixture of aldehyde, pyrazole, and the oxidant was heated at 55 °C for 3 h, and then, the product was isolated in analytically pure form via extraction with no need for column chromatography.

[Display omitted] • Oxidation of diols to lactones and dicarbonyl compounds using an oxoammonium salt bearing the nitrate anion. • Successful for the oxidation of a range of diol substrates. • Substoichiometric quantity of oxidant can be used. • Reaction involves a NO/NO 2 redox couple. The oxidation of diols to lactones, dialdehydes and diketones using a sub-stoichiometric quantity of an oxoammonium salt bearing the nitrate counterion is reported. In the case of linear aliphatic diols, when the diol substrate is shorter-chained, the lactone product predominates. When the chain is longer, the dialdehyde is the major product formed. A number of cyclic diols are also converted to their lactone, diketone or hydroxyketone congeners. [ABSTRACT FROM AUTHOR]

The conversion of ethyl 2-oxocyclohexanecarboxylate to ethyl salicylate using an oxoammonium salt is reported. The dehydrogenation reaction is operationally simple and compares favorably with previous literature examples for the same transformation and expands the scope of oxoammonium salts as reagents for oxidative functionalization processes.

An efficient and scalable route for the synthesis of nitriles was developed by oxoammonium salt (4-acetamido-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate) mediated oxidative conversion of aldehydes with NH 4 OAc. A variety of aliphatic aldehydes as well as benzaldehydes were converted into the corresponding nitriles in high yields. The nitroxyl radical which is the reduced species of the used oxoammonium salt was recovered by simple acid-base extraction for the recycling. [ABSTRACT FROM AUTHOR]

[Display omitted] The oxidation of alcohols to aldehydes and ketones using a sub-stoichiometric quantity of an oxoammonium salt bearing the nitrate counterion is reported. When the alcohol substrate is a liquid, the reaction can be performed solvent-free. When using a solid alcohol, the reaction can be performed either using a small volume of dichloromethane as a solvent, or else by leveraging mechanochemical activation. The methodology is applicable to the challenging oxidation of α-trifluoromethyl alcohols to the corresponding trifluoromethyl ketones. [ABSTRACT FROM AUTHOR]

A method for the oxidative cleavage of silyl ethers to their corresponding carbonyl species mediated by an oxoammonium salt is described. The resulting aldehydes and ketones are obtained under mild reaction conditions with no observed overoxidation. For robust substrates, heating to reflux temperatures significantly reduces the reaction time. [ABSTRACT FROM AUTHOR]

The water soluble oxidant 4-acetylamino-2,2,6,6-tetramethylpiperidine-1-oxoammonium tetrafluoroborate 1 oxidizes primary and secondary aliphatic, primary allylic, and primary and secondary benzylic alcohols to their corresponding aldehydes and ketones in aqueous media in good to excellent yields. [ABSTRACT FROM AUTHOR]

This review article summarizes the electron transfer reactions of piperidine aminoxyl radicals. Electrochemical studies revealed the single electron transfer nature of piperidine aminoxyl radicals. In solution, piperidine aminoxyl radicals serve as single electron transfer oxidation reagent to react with various biologically interesting molecules such as glutathione, cysteine, ascorbic acid, and amines. The reaction product distribution, reaction kinetics, intermediates, and the reaction features in biological mimic environments including micelles and cyclodextrins were investigated. Oxoammonium salts, the one-electron transfer oxidation products of piperidine aminoxyl radicals, are agents of organic synthesis to selectively generate ketones or di-ketones from alcohols or ketones bearing a-methylene group under mild conditions. The new reactions of oxoammonium salts with aromatic amines, phenols, heterocycles including phenothiazines, papaverine, and bilirubin are also illustrated. [ABSTRACT FROM AUTHOR]

The kinetics of the oxidation of a series of alcohols ( viz., ethanol, propan-2-ol, butan-1-ol, butan-2-ol, heptan-4-ol, decan-2-ol, propan-1,3-diol, butan-2,3-diol, cyclohexanol, benzyl alcohol, and borneol) with the oxoammonium salt 2,2,6,6-tetramethylpiperidine-1-oxyl chlorite in acetonitrile was studied by spectrophotometry. The products of oxidation of primary alcohols are the corresponding aldehydes and carboxylic acids, and the products of oxidation of secondary alcohols are ketones. The reaction rate is described by the second order equation. The rate constants and activation parameters were determined. The rate constant as a function of the alcohol nature is described by the one-parameter Taft equation. [ABSTRACT FROM AUTHOR]

The conversion of ethyl 2-oxocyclohexanecarboxylate to ethyl salicylate using an oxoammonium salt is reported. The dehydrogenation reaction is operationally simple and compares favorably with previous literature examples for the same transformation and expands the scope of oxoammonium salts as reagents for oxidative functionalization processes. [ABSTRACT FROM AUTHOR]

• Oxidation of alcohols using an oxoammonium salt bearing the nitrate counterion. • Sub-stoichiometric quantity of the oxidant is used. • Successful for the oxidation of a wide range of alcohol substrates. • Reaction involves an NO/NO 2 redox couple and a hydroxylamine/oxoammonium cycle. • Mechanism gives an insight into the nitric acid mediated oxidation of alcohols. A methodology for the oxidation of alcohols to the corresponding carbonyl compounds is reported using a sub-stoichiometric quantity of an oxoammonium salt bearing the nitrate counterion. The approach proves successful for the oxidation of a range of alcohol substrates including those bearing an oxygen atom β to the site of oxidation or an α-trifluoromethyl moiety. The mechanism of the reaction has been probed and also gives an insight into the previously reported nitric acid mediated oxidation of alcohols. [ABSTRACT FROM AUTHOR]