Dual signaling of m-chloroperbenzoic acid by desulfurization of thiocoumarin

The chemosignaling of widely used peracid oxidant of m-chloroperbenzoic acid (mCPBA) by the selective desulfurization of thiocoumarin was investigated. Thiocoumarin was efficiently converted into its corresponding coumarin by the reaction with mCPBA, and resulted in a pronounced fluorescent turn-on type signaling. The conversion also provided a significant change in absorption behavior which allowed a ratiometric analysis. The effective signaling could be used as a convenient determination method for mCPBA in aqueous environment.     

Epoxidation of syndiotactic 1,2-polybutadiene with peracids

The epoxidation of syndiotactic 1,2-polybutadiene (84 and 16% 1,2 and 1,4 units, respectively) with carboxylic peracids prepared in situ and m-chloroperbenzoic acid was studied. In the course of epoxidation in the presence of carboxylic peracids, oxirane groups are formed only through epoxidation of double bonds in the macromolecular backbone, whereas m-chloroperbenzoic acid is responsible for the chemical modification of 1,2 and 1,4 units of polybutadiene. The basic kinetic parameters of 1,2-polybutadiene epoxidation with peracids of various chemical structures were determined.     

Synthesis of sulfonamides promoted by alkyl iodide via a hypervalent iodine intermediate

Abstract

A new method for the preparation of sulfonamides from sodium sulfinates and amines is developed. A stoichiometric amount of m-chloroperbenzoic acid as oxidant and a catalytic amount of 1-iodopropane provides the corresponding sulfonamides in good yields under mild reaction conditions. In this protocol, 1-iodopropane is first oxidized by m-chloroperbenzoic acid into the corresponding hypervalent iodine intermediate iodosylpropane, which is highly unstable and decomposes at once to form hypoiodous acid. Then, the following reaction of the generated active hypoiodous acid with sodium sulfinates and amines results in the corresponding sulfonamides.     

Modification of silicon-substituted polynorbornenes by epoxidation of main chain double bonds

Postpolymerization modification of metathesis Si-containing polynorbornenes by epoxidation of double bonds of the main chain was carried out for the first time. New polynorbornenes containing one or two side Me₃Si substituents in a monomer unit and oxirane fragments in the main chain were obtained and characterized. Some features of epoxidation of polynorbornenes by 1.1-dimethyldioxirane (formed in situ) or m-chloroperbenzoic acid were studied. It was shown that m-chloroperbenzoic acid was an effective epoxidation agent, which did not affect Si?C bonds in polynorbornenes. It was found that the preparation of high-molecular-weight epoxidated polynorbornenes required one to introduce an oxidation inhibitor into the reaction mixture and to perform the reaction in toluene. Chlorine-containing solvents, such as chloroform and chlorobenzene, promoted the destruction of polynorbornenes. It was shown that the introduction of oxirane fragments into the polynorbornene main chain increased its T _g by 15?40°C.     

A convenient phosphoryloxylactonization of pentenoic acids with catalytic hypervalent iodine(III) reagent

A novel and convenient catalytic method for phosphoryloxylactonization of pentenoic acids is available: the cyclization of 4-pentenoic acids with phosphates using iodobenzene as a recyclable catalyst in combination with m-chloroperbenzoic acid as the terminal oxidant was easily carried out in CF₃CH₂OH at room temperature, giving phosphoryloxylactons in good yields, some of them had two diastereoisomers.     

Oxidative skeletal rearrangement of bicyclo[4.2.2]deca-2,4,7,9-tetraenes to bicyclo[4.3.1]deca-2,4,8-triene-7,10-diols and study of the antitumor activity of the products in vitro

Bicyclo[4.3.1]deca-2,4,8-triene-7,10-diols were synthesized in 76–85% yields by oxidative skeletal isomerization of the substituted bicyclo[4.2.2]deca-2,4,7,9-tetraenes of various structures on treatment with m-chloroperbenzoic acid. The structures of the obtained bicyclic unsaturated diols were reliably proven by modern spectral methods and X-ray diffraction. A high antitumor activity in vitro was found for bicyclo[4.3.1]deca-2,4,8-triene-7,10-diols against the Jurkat, K562, U937 and HL-60 tumor cell lines.     

Oxidation of arylamidoximes by various chemical and biomimetic systems: comparison with their oxidations by hemeproteins

Oxidation of 4-chlorobenzamidoxime by various chemical systems leads to the corresponding amide and nitrile, and to three dimeric compounds in greatly variable amounts as a function of the oxidizing agent. Monoelectronic oxidants, such as Pb(OAc)₄ and Ag₂CO₃, selectively led to 4-chlorobenzonitrile, whereas hydroperoxides such as H₂O₂ and tBuOOH only led to 4-chlorobenzamide. Other oxidants like m-chloroperbenzoic acid and Br₂ gave more complex mixtures. Introduction of an ironporphyrin catalyst in the oxidation performed by tBuOOH and m-chloroperbenzoic acid resulted in a spectacular increase of the formation of 4-chlorobenzonitrile. These results suggest that high-valent porphyrin ironoxo species preferentially oxidize arylamidoximes in a manner similar to monoelectronic oxidants.     

Fluorous dimethylthiocarbamate (DMTC) protecting groups for alcohols

N,N-Bis(perfluoroalkyl)thiocarbamoyl chlorides (^FDMTC-Cls) were synthesized as reagent for the protection of alcohols. Using the crystalline ^FDMTC-Cls, the ^FDMTC groups were introduced into the alcohol molecules in excellent yields in the presence of sodium hydride in THF at room temperature. The products were separated from the excess alcohols by solid-phase extraction with a fluorous reverse-phase silica gel column (Fluorous Solid Phase Extraction; FSPE). The ^FDMTC groups were readily removed by oxidation with m-chloroperbenzoic acid (m-CPBA) and subsequent hydrolysis with KHCO₃.     

An efficient chlorination of aromatic compounds using a catalytic amount of iodobenzene

An efficient method was developed for chlorination of aromatic compounds with electron-donating groups using iodobenzene as the catalyst and m-chloroperbenzoic acid as the terminal oxidant in the presence of 4-methylbenzenesulfonic acid in THF at room temperature for 24 h,and a series of the monochlorinated compounds was obtained in good yields.In this protocol,the catalyst iodobenzene was first oxidized into the hypervalent iodine intermediate,which then treated with lithium chloride and finally reacted with aromatic compounds to form the chlorinated compounds.     

m-Chloroperbenzoic acid-oxchromium (VI)-mediated cleavage of 2,4,5-trisubstituted oxazoles

An array of 2-substituted-4,5-diphenyloxazoles were found to be cleaved to triacylamines and diacylamines (imides) using a reagent system composed of m-chloroperbenzoic acid (MCPBA) and 2,2′-bipyridinium chlorochromate (BPCC). The 2-alkyl-4,5-diphenyloxazoles give imides (38–60%) as the predominant cleavage product while the 2-aryl-4,5-diphenyloxazoles give triacylamines (44–71%). Two mechanisms involving intermediates such as cyclic endoperoxides or oxachromacycles were proposed. An application of the oxidative cleavage to the multi-step synthesis of (±)-phoracantholide I seco acid is detailed.     

Oxidation of some alkoxy-cycloheptatriene derivatives: unusual formation of furan and furanoids from cycloheptatrienes

The oxidation of some alkoxy tropone and tropone ketal derivatives with singlet oxygen and m-chloroperbenzoic acid was investigated. In most cases furan and furanoid derivatives were isolated. The structures of the formed products were determined by means of spectral data and the formation mechanism of these unusual products is discussed.     

Synthesis of polyfunctional β-Ketosulfides and their reactions with m-chloroperbenzoic acid and chlorine dioxide

The reaction of bromoacetophenone with various thiols furnished β-ketosulfides: 2-(1-methyl-1H-imidazol-2-ylsulfanyl)-1-phenylethanone, 2-(1H-imidazol-2-ylsulfanyl)-1-phenylethanone, 2-(2-hydroxyethylsulfanyl)-1-phenylethanone. β-Ketosulfoxides were obtained by the oxidation of β-ketosulfi des with m-chloroperbenzoic acid and chlorine dioxide.     

Convenient sulfonylation of benzotriazoles with the in situ–generated sulfonyl bromides

A convenient procedure is developed for the preparation of N-sulfonylbenzotriazoles from sodium sulfinates, benzotriazoles, and sodium bromide in the present of m-chloroperbenzoic acid as oxidant. This radical sulfonylation proceeds efficiently at room temperature under neutral conditions, affording the corresponding N-sulfonylbenzotriazoles in moderate to good yields in a short time.     

Stereochemical study on an oxygen-directed olefin oxidation and subsequent oxygen cyclization: Differences between peracid and metal oxide-catalyzed hydroperoxide in oxidation reactions

Optically active (2S,4R)-2-hydroxy-4-pentyl enol ether was prepared for the first time and subjected to hydroxy-directed oxidations at the olefinic group. Treatment with m-chloroperbenzoic acid and tert-butyl hydroperoxide/vanadium acetylacetonate resulted in the same stereoface differentiation at the olefin, with diastereomeric excesses as high as 79% and 92%, respectively, whereas the stereochemistry of the products of subsequent nucleophilic additions of the hydroxy group was opposite.     

Synthesis of 4-aminopyrazolo[3,4-d]pyrimidine derivatives from 5-acetyl-6-amino-4-methylsulfanyl- or 5-acetyl-6-amino-4-methylsulfonylpyrimidines

Diacetyl ketene N,S-acetal was used for the synthesis of 5-acetyl-6-amino-4-methylsulfanylpyrimidines substituted at the exocyclic nitrogen atom, which were further oxidized with m-chloroperbenzoic acid to the corresponding methylsulfonylpyrimidines. Reactions of hydrazines with these pyrimidines containing vicinal Ac and MeS (or MeSO₂) groups were used for the preparation of new 4-aminopyrazolo[3,4-d]pyrimidine derivatives.     

Siliciumverbindungen mit starken intramolekularen sterischen wechselwirkungen: XVIII. Oxa-, thia- und selena-trisiletane durch ringerweiterungsreaktionen

The reaction of hexa-t-butylcyclotrisilane with sulfur or selenium gives the corresponding thia- and selena-trisiletanes. Oxidation of the same cyclotrisilane by oxygen, dimethylsulfoxide, or m-chloroperbenzoic acid leads to three oxidation products which possess one, two, or three oxygen atoms, respectively in the ring system.     

Determination of phenolic compounds using high-performance liquid chromatography with Ce-Tween 20 chemiluminescence detection

A novel method for the simultaneous determination of phenolic compounds such as salicylic acid, resorcinol, phloroglucinol, p-hydroxybenzoic acid, 2,4-dihydroxybenzoic acid, and m-nitrophenol by high-performance liquid chromatography (HPLC) coupled with chemiluminescence (CL) detection was developed. The procedure was based on the chemiluminescent enhancement by phenolic compounds of the cerium(IV)-Tween 20 system in a sulfuric acid medium. The separation was carried out with an isocratic elution or with a gradient elution using a mixture of methanol and 1.5% acetic acid. For six phenolic compounds, the detection limits (3σ) were in the range 1.40-5.02 ng/ml and the relative standard deviations (n=11) for the determination of 0.1 μg/ml compounds were in the range 1.9-2.9%. The CL reaction was well compatible with the mobile phase of HPLC, no baseline drift often occurred in HPLC-CL detection was observed with a gradient elution. The method has been successfully applied to the determination of salicylic acid and resorcinol in Dermatitis Clear Tincture and p-hydroxybenzoic acid in apple juices.     

A new finding in selective Baeyer-Villiger oxidation of α-fluorinated ketones; a new and practical route for the synthesis of α-fluorinated esters

α-Fluorinated esters were effectively prepared by the Baeyer-Villiger oxidation of α-fluorinated ketones with m-chloroperbenzoic acid (m-CPBA) under mild conditions. The yield of the esters was influenced by the choice of solvent, base, and substituent on the aryl group of the ketones. 4-Methoxyphenyl substituted fluoroketones were oxidized almost quantitatively with m-CPBA within 10 min to 12 h at room temperature using 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a cosolvent with CH₂Cl₂ (1:1, v/v) and aqueous buffer (KH₂PO₄-NaOH, pH 7.6) as an additive base. The oxidation reaction rates of α-fluorinated ketones were higher than those of the corresponding non-fluorinated ketones. The fluorine atom at α-position of fluoromethyl aryl ketones enhanced the reactivity in the Baeyer-Villiger oxidation.     

Diastereoface-differentiating oxidation of 1-cyclohexenyl ether using a 2,4-pentanediol tether

Diastereoface-differentiating oxidation of the chiral enol ether prepared from cyclohexanone and optically active 2,4-pentanediol gave a diastereomeric mixture of the corresponding 2-hydroxycyclohexanone acetal. The diastereomeric excess of the product reached over 99% by oxidation with m-chloroperbenzoic acid at −78°C. Oxidation with t-butyl hydroperoxide in the presence of metal catalysts also resulted in high diastereomeric excesses of up to 97%.     

Iodoarene-catalyzed one-pot preparation of 2,4,5-trisubstituted oxazoles from alkyl aryl ketones with mCPBA in nitriles

2,4,5-Trisubstituted oxazoles could be easily prepared in moderate yields by the reaction of alkyl aryl ketones, iodoarene, m-chloroperbenzoic acid, and trifluoromethanesulfonic acid in acetonitrile, propionitrile, butyronitrile, and isobutyronitrile, respectively. Here, reactive aryliodonium I(III) species is formed in situ by the reaction of iodoarene with mCPBA and trifluoromethanesulfonic acid, and the formed aryliodonium I(III) species reacts with alkyl aryl ketone to form β-keto aryliodonium species. This in turn, reacts with nitrile to form the corresponding oxazole. Iodoarene works as a catalyst. However, one equivalent of iodoarene is required because one equivalent of reactive aryliodonium I(III) species must be formed prior to the reaction with alkyl aryl ketone. Then, by introducing an ionic liquid group into iodoarene, to form ionic liquid-supported iodoarene, the isolation procedure of oxazole could be simplified. The addition of ethyl acetate to the reaction mixture, washing of the reaction mixture with aq NaHCO₃, removal of ethyl acetate, and extraction of the residue with ether provided oxazoles in moderate purity, and the residual ionic liquid-supported iodoarene could be reused in the same reaction.