A ‘waterproof’ catalyst for the oxidation of secondary amines to nitrones with alkyl hydroperoxides

Catalytic oxidation of secondary amines to nitrones using alkyl hydroperoxides as primary oxidant has been demonstrated for the first time. The titanium alkoxide catalyst is protected from co-product water by the combined use of a tightly binding trialkanolamine ligand and molecular sieves. Nitrones can be obtained in high yield (up to 98%) under homogeneous, anhydrous conditions and even in the absence of solvent. The reactions are fast (2-7 h) and good selectivity can be achieved with as little as 1% catalyst.     

A new specific mechanism for the acid catalysis of the addition step in the Baeyer-Villiger rearrangement

[structure: see text] A new transition state of the addition step in the Baeyer-Villiger reaction was found. The role of proton acceptor is played by the carbonyl oxygen atom, and the free energy barrier is 12.7 kcal/mol lower than that previously reported. This finding changes the mechanism for the acid catalysis and could be of interest for similar reactions in which it is known that such catalysis occurs, especially in nonpolar solvents.     

Substituent effects in the migration step of the Baeyer-Villiger rearrangement. A theoretical study

Quantum mechanical calculations have been performed on the migration step of the Baeyer-Villiger (BV) rearrangements of some acetophenones, p-RC6H4COCH3 (R = CN, Cl, H, CH3, CH3O) with m-chloroperbenzoic acid. The energy barriers, charge distributions, and frontier molecular orbitals determined for the aryl migration step explain the effects of substituents on the reactivity of these ketones. A plot of the log of relative oxidation rates of the ketones versus their corresponding calculated energy barriers of the migration stage showed a downward deviation for the p-OCH3 derivative. This result is consistent with a change in the rate-determining step, from the aryl migration to the carbonyl addition, in the case of p-methoxyacetophenone, according to the suggestion that the rate-determining step of the BV oxidation can change with variations in the substituent group.     

Cation-radical oxidation step in the nitration of phenothiazine with nitric acid

A phenothiazine cation radical, which was isolated preparatively in the form of the perchlorate in the reaction of phenothiazine with the minimum amount of nitric acid in aqueous perchloric acid, is formed initially in the nitration of phenothiazine with nitric acid to give 3-nitrophenothiazine S-oxide. The perchlorate is also converted to the nitro compound by nitration. During nitration the phenothiazine cation radical is oxidized to the phenazthioniuin cation, the perchlorate of which was also isolated preparatively in the reaction of phenothiazine with HNO₃ in amounts that were twice the amount required for the formation of the phenothiazine cation radical. This is followed by the formation of the nitro derivative, which involves the reaction of the phenazthionium cation with the nitrite anion of nitrous acid. The resulting 3-nitrophenothiazine is then converted to the final product.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1214–1216, September, 1981.     

Liquid-phase oxidation of alkylaromatic hydrocarbons and their cyclohexyl derivatives to hydroperoxides in the presence of phthalimide catalysts

Regularities of liquid-phase oxidation the alkyl aromatic hydrocarbons and their cyclohexyl derivatives to hydroperoxides at presence of phthalimide catalysts are studied. It is established that N-hydroxylphthalimide increases the speed of oxidation of these hydrocarbons and provides high selectivity of formation of their hydroperoxides.     

A single step solid-phase extraction method for complete separation of sterol oxidation products in food lipids

One of the crucial steps in determination of sterol oxidation products (SOPs) in foods is their enrichment and purifications by various preparative methods for further analysis by GC and GC–MS. Among the preparative methods, SPE of various adsorbents and solvent systems, are being used most widely. At present, no single step SPE method is suitable to completely separate the SOPs. In this study, a SPE (1 g silica) method, suitable for both transesterified and cold saponified oil samples, was developed to separate completely SOPs from other lipid components. This method resulted in high recovery from rapeseed oil of added 5β,6β-epoxycholestan-3β-ol (94-96%), cholest-5-en-3β-ol-7-one(94%), cholestane-3β,5α,6β-triol (88–91%), cholest-5-en-3β,7α-diol and 5α,6α-epoxycholestan-3β-ol (88–90%). The method has a high sample capacity of up to 1 g transesterified or cold-saponified oil sample. The method was tested and applied to different vegetable oils and to monitor the effects of refining processes on POPs in hazelnut oil.     

Role of water in the oxidation of furfural with hydrogen peroxide

The oxidation of furfural with hydrogen peroxide in water and in absolute ether containing small amounts of water was studied. It was found that water inhibits the formation of furfuryl hydroxyhydroperoxide but promotes the buildup of acids. The accumulated acids play a catalytic role in all stages of the process.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1453–1456, November, 1972.     

A new alkaline rearrangement of the benzofuran skeleton. One step transformation of 2-(2-benzofuranyl)benzonitriles into (Z)-phenylmethyleneisoindolinones

The alkaline hydrolysis of 2-(2-benzofuranyl)benzonitriles 2 by potassium hydroxide under reflux in ethanol stops at the corresponding amides 5 . Using other solvents (ethylene glycol or methoxyethanol) at higher temperatures, one can obtain either the amides 5 , the acids 1 or rearrangement products depending on the experimental conditions. The rearrangement products were identified as (Z)phenylmethylenedihydroisoindolinones 6 resulting from opening of the furan ring. The structures of the compounds 6 were established by ¹H nmr spectroscopy (nOe) and X-ray crystallography.     

Role of the solvent in the oxidation of furfural with hydrogen peroxide

The effect of the nature of the solvent on the direction and rate of oxidation of furfural by hydrogen peroxide was studied. The use of alcohol and dioxane as the solvents substantially increases the selectivity of the process and leads to the primary formation of furfural hydroxyperoxides (the -hydroxyhydroperoxide in dioxane, and the , -dihydroxyperoxide in alcohol). The polarity of the medium and specific solvation have a substantial effect on the rate of formation of the peroxides. The effect of specific solvation predominates.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 603–607, May, 1977.     

Vanadium-catalyzed selenide oxidation with in situ[2,3] sigmatropic rearrangement (SOS reaction): scope and asymmetric applications

A vanadium-catalyzed method for the oxidation of prochiral aryl, allylic selenides with tandem [2,3] sigmatropic rearrangement has been developed. This protocol has been screened on a series of substrates to test for its generality and effectiveness. The applicability of this methodology to the synthesis of enantiomerically enriched allylic alcohols has been studied on a series of chiral oxazole-containing systems with a diastereomeric ratio (d.r.) of up to 85 : 15. The chiral transfer observed in the allyl alcohol products is the result of a net 1,9- and/or 1,10-induction. Finally, the first example of a selenium-oxygen nonbonding interaction in oxazole-containing selenide appears to have been observed via X-ray crystal analysis.     

A comparison between the use of a redox mediator in solution and of surface modified electrodes in the electrocatalytic oxidation of nicotinamide adenine dinucleotide

Cyclic voltammetry was successfully applied to study the oxidation of nicotinamide adenine dinucleotide (NADH) both in homogeneous and heterogeneous phase. The first case was realized with a solution containing p-methylamino-phenolsulphate (MAP) as redox mediator and the diaphorase (DI) from Clostridium kluveri as enzyme while the second one by using both a glassy carbon (GC) and a carbon nanotube paste (CNTP) electrode modified with electrodeposited films derived from 3,4-dihydroxybenzaldehyde (3,4-DHB). Such systems were successively coupled with glucose dehydrogenase (GDH) reaction to realize the redox chain present in glucose biosensors. A critical comparison of the two systems was also reported.     

A new methodology for the oxidation of sulfides with Fe(III) catalysts

A variety of sulfides were converted to the corresponding sulfoxide derivatives with 70% t‐BuOOH (water) as the oxidant in the presence of catalytic quantity of Fe₂(SO₄)₃. The method described has a wide range of applications, involves simple work‐up, exhibits chemoselectivity/enantioselectivity and proceeds under mild reaction conditions. The resulting products are obtained in good yield within a reasonable time. Copyright © 2012 John Wiley & Sons, Ltd.     

A simple and advantageous protocol for the oxidation of alcohols with O-iodoxybenzoic acid (IBX)

[reaction: see text] An efficient, user-friendly procedure for the oxidation of alcohols using IBX is described. Simply heating a solution of the alcohol in the presence of suspended IBX followed by filtration and removal of the solvent gives excellent yields of the corresponding carbonyl compounds. We illustrate this procedure with a panel of primary and secondary alcohol substrates and note that it allows recycling and reuse of the oxidant.