Mild and chemoselective catalytic deprotection of ketals and acetals using cerium(IV) ammonium nitrate

Cerium(IV) ammonium nitrate (CAN) is a powerful, though mild, reagent for the efficient and selective removal of a range of ketals and acetals. This novel deprotection method requires only catalytic amounts of CAN and tolerates a variety of functional and protecting groups. Mechanistic insights suggest that the Ce(IV) salts act as unique Lewis acids and not as redox active species.     

Preparation of naphthaldehydes by cerium(IV)ammonium nitrate oxidation of methylnaphthalenes

Naphthalenes with an Me group in the 1-position gave aldehydes in good to excellent yields when oxidized with cerium(IV) ammonium nitrate (CAN) in 50% HOAc at 85°. Under the same conditions methylnaphthalenes with no Me group in a peri position gave aldehydes in fair yields but also significant amounts of 1,4-naphthoquinone.     

Photochemical nitrooxylation of methylbenzenes by cerium(IV) ammonium nitrate in acetonitrile

The photochemical reaction of substituted toluenes with CAN in CH₃CN leads to good yields of benzyl nitrates under very mild conditions.     

Formation of monoaldehydes by cerium(IV) ammonium nitrate oxidation of unsymmetric dimethylnaphthalenes

When 1,2-, 1,3-and 1,6-dimethylnaphthalene are oxidized by Ce⁴⁺ in acetic acid the corresponding monoaldehydes are formed in better than 80% yield. In each case aldehyde formation takes place with a high degree of selectivity as the methyl-1- to methyl-2-naphthaldehyde ratio is better than 11:1. The selectivity may be explained from differences in reactivity as calculated within the frontier orbital method.     

Bromination of cyclopropanes using potassium bromide and cerium(IV) ammonium nitrate (CAN): synthesis of 1,3-dibromides

The bromination of cyclopropanes using potassium bromide and cerium(IV) ammonium nitrate (CAN) in a two-phase system consisting of water and dichloromethane affording 1,3-dibromides in excellent yields is reported.     

Regioselective nitration of N,N-dialkylanilines using cerium(IV) ammonium nitrate in acetonitrile

A highly regioselective and inexpensive nitration of N,N-dialkylanilines by cerium(IV) ammonium nitrate (CAN) in acetonitrile under room temperature to yield p-nitryl-N,N-dialkylanilines in good yields was reported.     

Facile synthesis of 1,2,3-tricarbonyls from 1,3-dicarbonyls mediated by cerium(IV) ammonium nitrate

A mild and efficient protocol for the synthesis of vicinal tricarbonyl compounds from β-dicarbonyls in a single step using cerium(IV) ammonium nitrate as a catalytic oxidant is described. Ease of execution, wide substrate scope and the suitability for the synthesis of commercially important compounds like ninhydrin, alloxan and oxoline make this reaction particularly noteworthy.     

Electron transfer reactions of 1-phenyl-4-vinylpyrazole mediated by cerium(IV) ammonium nitrate

Summary The title compound is converted into the cyclic ethers5 and the alcohol6 upon treatment with ceric ammonium nitrate in acetone. Using methanol as a solvent the dimethoxy derivative9 and the nitrate ester10 are formed. No cross cycloaddition is observed in the presence of olefins such as ethyl vinyl ether,DMAD, or indene; however, with cyclopentadiene as co-reagent a mixture of the exo-endo Diels-Alder adducts14 involving the vinylic system of 1 as 2 component is obtained. The results are rationalized through the interrnediacy of the radical cation1 ^·+, generated by single electron transfer (SET) from the neutral precursor1 to Ce(IV).

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Elektrontransfer-Reaktionen von 1-Phenyl-4-vinylpyrazol mittels Cer(IV)-Ammonnitrat

Zusammenfassung Die Titelverbindung wurde mittels Cer(IV)-Ammonnitrat in Aceton in die cyclischen Ether5 und den Alkohol6 umgewandelt. Mit Methanol als Lösungsmittel wurde das Dimethoxyderivat9 und der Nitratester10 gebildet. Bei Anwesenheit von Olefinen wie etwa Ethylvinylether,DMAD oder Inden wurden keine Cross-Cycloadditionen beobachtet. Hingegen wurde mit Cyclopentadien als Mitreagens eine Mischung vonexo-endo-Diels-Alder-Produkten14 erhalten, wobei das vinylische System von1 als 2-Komponente fungiert. Die Ergebnisse werden mittels eines intermediär auftretenden Radikalkation1 ^·+ als Produkt eines Einelektronentransfers (SET) des neutralen Vorläufers1 zu Ce(IV) rationalisiert.

     

Oxidative breakdown of polymeric plutonium(IV) hydroxide by cerium(IV)

The breakdown of polymeric plutonium(IV) hydroxide (plutonium colloid) by cerium(IV) has been studied spectrophotometrically by monitoring the formation of plutonium(VI). Reaction rate variations were studied with changes in cerium(IV), acid and plutonium colloid concentrations. A reaction mechanism involving the formation of [Ce₂O(OH)₂]⁴⁺ and its reaction with the polymer surface to produce two plutonium(V) ions is postulated to explain the observed kinetic data, in particular the maximum in the reaction rate at around 0.3 M nitric acid.     

A mild and efficient procedure for the oxidation of epoxides and aziridines using cerium(IV) ammonium nitrate and NBS

The CAN and NBS combination has been used for the first time for the synthesis of versatile α-hydroxy ketones and α-amino ketones from oxiranes/aziridines, respectively, in excellent yields. This method is a direct, one-pot, synthesis under mild conditions using acetonitrile-water (9:1) as solvent.     

The role of nitrate free radicals in the photochemical side-chain nitrooxylation of alkylbenzenes by cerium(IV) ammonium nitrate in acetonitrile

It is suggested that the reactive species in the CAN-induced photochemical side-chain nitrooxylation of alkylbenzenes is the nitrate radical, which probably acts as one-electron oxidant.     

New and efficient method for esterification of carboxylic acids with simple primary and secondary alcohols using cerium(IV) ammonium nitrate (CAN)

The esterification of phenylacetic acids and cis-oleic acid with primary and secondary simple alcohols, which also act as solvents using cerium(IV) ammonium nitrate (CAN) at room temperature gave phenylacetates and methyl (9Z)-octadec-9-enoate. The reactions, which occur under relatively mild conditions, afforded the desired products in good to excellent yields.     

Dimethyl arylmalonates from cerium(IV) ammonium nitrate promoted reactions of dimethyl malonate with aromatic compounds in methanol

Aromatic compounds undergo homolytic malonylation by reaction with cerium(IV) ammonium nitrate and dimethyl malonate in methanol at room temperature.     

Heterogeneous water oxidation by bidentate Schiff base manganese complexes in the presence of cerium(IV) ammonium nitrate

Oxygen evolution was observed upon mixing solid manganese(III) bidentate Schiff base complexes with aqueous solutions of cerium(IV) ammonium nitrate. However, oxygen evolution was not observed upon mixing solutions of the complexes (in acetonitrile) with Ce(IV). Electron-withdrawing substituents on the Schiff base ligands (NO₂, Br) enhanced the reactivity of the manganese complexes toward oxygen evolution. Oxygen evolution was also affected by R groups on the ligands, in the order Me > Et ≫ Bz. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Regioselective radical addition of 3-oxopropanenitriles with terminal dienes promoted by cerium(IV) ammonium nitrate and manganese(III) acetate

Radical addition of 3-oxopropanenitriles to 1,3-butadiene derivatives promoted by (NH₄)₂Ce(NO₂)₆ and Mn(OAc)₃ afforded 5-ethenyl-4,5-dihydrofuran-3-carbonitriles in low to good yields. These dihydrofurans were characterised by IR, ¹H-NMR, ¹³C-NMR and HRMS spectra. All radical additions performed via CAN and Mn(OAc)₃ were occurred on the terminal double bond on dienes. A mechanism for the formation of the dihydrofurans was proposed.     

Cerium (IV) ammonium nitrate catalyzed photochemical autoxidation of alkylbenzenes

The autoxidation of alkylbenzenes can be promoted photochemically in the presence of catalytic amounts of cerim (IV) ammonium nitrate (CAN) under very mild conditions, the efficiency of the process being significantly increased by added acids. It is suggested that the reaction is promoted by NO₃, radicals formed in the light induced decomposition of CAN and that Ce(III) may be reoxidized to Ce(IV) by benzylperoxy radicals.     

Selective and efficient oxidation of sulfides to sulfoxides using ammonium cerium (IV) nitrate in the presence of a catalytic amount of KBr or NaBr

A wide range of aliphatic or aromatic sulfides are selectively oxidized to the corresponding sulfoxides using ammonium cerium (IV) nitrate (CAN) and a catalytic amount of KBr or NaBr in the presence of wet SiO₂ in CH₂Cl₂ under heterogeneous conditions in moderate to high yields.     

Selective and efficient oxidation of sulfides to sulfoxides using ammonium cerium (IV) nitrate in the presence of a catalytic amount of KBr or NaBr

A wide range of aliphatic or aromatic sulfides are selectively oxidized to the corresponding sulfoxides using ammonium cerium (IV) nitrate (CAN) and a catalytic amount of KBr or NaBr in the presence of wet SiO₂ in CH₂Cl₂ under heterogeneous conditions in moderate to high yields. Correspondence: Mohammad Ali Zolfigol, Faculty of Chemistry, Bu-Ali Sina University, P.O. Box 6517838683, Hamadan, Iran; Kamal Amani, Department of Chemistry, Faculty of Science, University of Kurdistan, P.O. Box 6617715175, Sanandaj, Iran.