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.     

Cerium(IV) ammonium nitrate mediated thiocyanation of dienes: Some interesting observations

Various 1,3-dienes when treated with a solution of cerium(IV) ammonium nitrate and ammonium thiocyanate in acetonitrile afforded the isothiocyanatothiocyanates via a [3,3] sigmatropic rearrangement. Electron rich dienes afforded the γ-thiocyanato-α,β-unsaturated carbonyl compounds under similar experimental conditions.     

Cerium(IV) ammonium nitrate: Reagent for the versatile oxidative functionalization of styrenes using N-hydroxyphthalimide

Cerium(IV) ammonium nitrate was found to be a versatile reagent for the oxidative functionalization of styrenes using N-hydroxyphthalimide and iodine affording three different types of products with oxyphthalimide, nitrate and iodide groups. It was shown that reaction of styrenes with N-hydroxyphthalimide and cerium(IV) ammonium nitrate can be selectively directed to oxynitro-oxyphthalimides and dioxyphthalimides depending on the reaction conditions, in particular a solvent. Reaction of styrenes with iodine under the action of N-hydroxyphthalimide and cerium(IV) ammonium nitrate leads to the formation of iodo-oxyphthalimides.     

Cerium (IV) ammonium nitrate (CAN)-mediated regioselective synthesis and anticancer activity of 6-substituted 5,8-dimethoxy-1,4-naphthoquinone

6-Substituted 5,8-O-dimethyl-1,4-naphthoquinones (6-DMNQ), the promising anticancer scaffolds, were selectively generated by oxidative demethylation of 2-substituted 1,4,5,8-tetramethoxynaphthalenes with CAN in EtOAc/H₂O in comparatively high yields. An interesting finding was that apart from the reported electron-withdrawing effects of substituents on position 2 of naphthalene ring, regioselective synthesis of 6-DMNQ was largely dependent on the steric effects in CAN-mediated oxidation. The selective cytotoxicities of 6-DMNQ from the in vitro cell-based assays were exhibited between the cancer cells and normal cells. Moreover, most of sulfur-containing 6-DMNQ derivatives displayed better anticancer activities than the corresponding oxygen-containing ones, which could provide an available strategy for the design of 6-DMNQ derivatives as potential anticancer agents.     

Cerium(IV)ammonium nitrate(CAN)initiated O-alkylation of oximes with N-vinyl lactams

O-Alkylation of oximes with N-vinylpyrrolidin-2-one or iV-methyl-N-vinylacetamide was efficiently initiated by a catalytic amount of cerium(IV)ammonium nitrate(CAN), giving the corresponding oxime ether derivatives in good yield.     

A sequential synthesis of substituted furans from aryl alkynes and ketones involving a cerium(IV) ammonium nitrate (CAN)-mediated oxidative cyclization

A convenient, two-step synthesis of substituted furans from readily available aryl alkynes and ketones is reported. The furan-forming oxidative cyclization is mediated by the combination of cerium(IV) ammonium nitrate and potassium bromide and can be carried out in an open flask.     

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.     

Cerium(IV) ammonium nitrate (CAN) catalyzed aza-Michael addition of amines to α,β-unsaturated electrophiles

Cerium(IV) ammonium nitrate (CAN) catalyzed facile and efficient aza-Michael addition of aromatic and aliphatic amines with α,β-unsaturated electrophiles in the absence of solvent under ultrasound irradiation.     

Cerium(IV)-mediated C-C bond formations in carbohydrate chemistry

We provide a comprehensive study on the addition of radicals to unsaturated carbohydrates in the presence of cerium(IV) ammonium nitrate (CAN). The method is applicable to hexoses, pentoses, and disaccharides, tolerates different protecting groups, and is characterized by mild reaction conditions. Best substrates are malonates and glycals, which afford 2-C-branched carbohydrates in high yields and stereoselectivities. For the first time, the anomeric radicals were trapped with nucleophiles after oxidation and thus the 1- and 2-position of glucose were functionalized in one step. Nitro compounds are suitable CH acidic radical precursors as well, offering an easy access to C-analogs of glycosamines in moderate to good yields. Finally, selective reductions demonstrate the synthetic potential of cerium(IV)-mediated radical reactions in carbohydrate chemistry.     

Nitrophenol Derivatives Oxidized by Cerium(IV) Ammonium Nitrate (CAN) and Their Cytotoxicity

Oxidation of a series of phenols with cerium(IV) ammonium nitrate (CAN) in acetonitrile under mild conditions yields the mixture of corresponding nitrophenols. In the cases of methylphenols and hydroxy ‐carboxylic acids, the steric effect may reduce the nitration reaction. Compounds 3a and 4b showed selective activities to Hep 3B and Hep G2 cancer cell lines, respectively. Compound 2c showed selective activities to Hep G2 and MDA‐MB‐231 cancer cell lines. Furthermore, compound 10b showed selective activities to Hep G2, Hep 3B, MCF‐7 and MDA‐MB‐231 cancer cell lines.     

Cerium(IV) ammonium nitrate catalyzed synthesis of α-dehydro-β-amino esters

α-Dehydro-β-amino esters have been synthesized regioselectively from acetates of Baylis-Hillman adducts with amines in the presence of a catalytic amount of ceric ammonium nitrate (CAN) in good yield. The regioselectivity does not differ with respect to the polarity of the solvent.     

Ceric (IV) ammonium nitrate (CAN) mediated synthesis of pyrrole-2,3,4,5-tetracarboxylates by reaction of dimethyl acetylenedicarboxylate with an amine

A simple one-step method for efficient synthesis of pyrrole-2,3,4,5-tetracarboxylates by reaction of dimethyl acetylenedicarboxylate with an amine using ceric (IV) ammonium nitrate as one electron oxidant is described.     

硫酸高铈催化炔烃的水合反应研究

炔烃经水合反应生成酮是有机合成中最重要和最基本的进行官能团转换的方法之一. 我们提供了一种价廉且具有高选择性的硫酸高铈催化炔烃水合方法. 实验结果表明: 在硫酸高铈(0.1 mmol)、浓硫酸(0.06 mL)、水(0.02 mL)和苯(5 mL)且反应温度为70 ℃的反应条件下, 炔烃(1 mmol)可以顺利发生水合反应生成酮.     

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.     

Esterification‐nitration of Ortho‐hydroxyphenyl Carboxylic Acids and Benzoic Acids with Cerium(IV) Ammonium Nitrate (CAN)

A convenient and useful esterification was realized, and this reaction proceeded without a dehydrating reagent or water removal equipment. A series of ortho‐hydroxyphenyl carboxylic acids and benzoic acids were transformed to their corresponding methyl esters under CAN/CH₃OH reaction conditions. Whereas in an aprotic solvent, acetonitrile, sp³‐C tethered ortho‐hydroxyphenyl carboxylic acids undergo simultaneous o,p‐dinitration and intramolecular esterification reactions in good yields. Also, 2‐((1 E)‐2‐nitrovinyl)‐4‐nitro‐phenol ( 3e ) showed selective cytotoxicities toward MCF‐7, HEP G2, and HEP 3B cell lines with IC₅₀ values of 23.50, 7.33, and 7.59 ug/mL, respectively.     

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-mediated reactions: Simple route to benzimidazole derivatives

The reaction of o-phenylenediamine with aromatic aldehydes in MeOH at room temperature catalyzed by cerium (IV) ammonium nitrate (CAN) afforded either 2-aryl-1-arylmethyl-1H-benz-imidazoles and/or 2-aryl-substituted benzimidazoles.     

Kinetics of Central Ion Electroreduction in Cerium (IV)-Decatungstate

A general characteristics is given to the kinetics of electroreduction of cerium-decatugstate anions on mercury, polycrystalline gold, and the pyrolytic-graphite basis plane in acetate buffer solutions (pH 3.5-6.0). Based on the analysis of UV absorption spectra, the ratio of two reactant forms differing in the protonation degree in solutions under study is estimated. At a negatively charged mercury electrode, the reduction of the Ce(IV) central ion is shown to proceed as an outer-sphere process with classical manifestations of the psi-prime effect (polarization curves reveal a current minimum which deepens with supporting electrolyte dilution and an increase in the reactant negative charge). On the positively charged surface, the current is observed to increase with an increase in the supporting electrolyte concentration, which is interpreted in terms of the strong adsorption of the reactant and its coadsorption with cations. The gold electrode demonstrates pronounced effects of strong chemisorption. Adsorption complications observed on pyrolytic graphite are shown to become strongther for surfaces with more pronounced nonideal behavior. For low concentrations of atomar steps (apparently, for low coverages of pyrolytic-graphite surface with the adsorbed reactant), the quasireversible electron transfer with the rate increasing with increasing pH is observed.     

硫酸溶液中胶束催化Ce(IV)氧化D-甘露糖

Kinetics of D-mannose oxidation by cerium (IV) was studied in a sulfuric acid medium at 40℃ both in absence and presence of ionic micelles. In both cases, the rate of the reaction was first-order in D-mannose and in cerium(Ⅳ), which decreased with increasing [H2SO4]. This suggested that the redox reaction followed the same mechanism. The reaction proceeded through formation of an intermediate complex, which was proved by kinetic method. The complex underwent slow unimolecular decomposition to a free radical that reacted with cerium (Ⅳ) to afford the product. The catalytic role of cationic cetyltrimethylammonium bromide (CTAB) micelles was best explained by the Menger-Portnoy model. The study of the effect of CTAB also indicated that a negatively charged species was reactive form of cerium (Ⅳ). From the kinetic data, micelle-cerium (Ⅳ) binding and rate constants in micellar medium were evaluated.The anionic micelle of sodium dodecyl sulfate plays no catalytic role. The oxidation has the rate expression --d[Ce(Ⅳ)]= k1Kcl[D-mannose] [Ce(Ⅳ)]dt Different activation parameters for micelle catalyzed and uncatalyzed paths were also calculated and discussed.     

Micelle Catalyzed Oxidation of D-Mannose by Cerium (IV) in Sulfuric Acid

Kinetics of D-mannose oxidation by cerium (IV) was studied in a sulfuric acid medium at 40°C both in absence and presence of ionic micelles. In both cases, the rate of the reaction was first-order in D-mannose and cerium (IV), which decreased with increasing [H₂SO₄]. This suggested that the redox reaction followed the same mechanism. The reaction proceeded through formation of an intermediate complex, which was proved by kinetic method. The complex underwent slow unimolecular decomposition to a free radical that reacted with cerium (IV) to afford the product. The catalytic role of cationic cetyltrimethylammonium bromide (CTAB) micelles was best explained by the Menger-Portnoy model. The study of the effect of CTAB also indicated that a negatively charged species was the reactive form of cerium (IV). From the kinetic data, micelle-cerium (IV) binding and rate constants in micellar medium were evaluated. The anionic micelle of sodium dodecyl sulfate plays no catalytic role. The oxidation has the rate expression: -d[Ce(IV)]=k1Kc1[D-mannose][Ce(IV)]dt Different activation parameters for micelle catalyzed and uncatalyzed paths were also calculated and discussed.