- Identification of acrolein from the ozone oxidation of unsaturated fatty acids
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By-products of lipoperoxidation reactions may be associated with the genesis or the progression of several diseases as arteriosclerosis, diabetes and cancer, among many others. Acrolein, at first a widely distributed environmental pollutant, is currently known as a compound capable of being generated as a result of metabolic reactions within biological systems, highly toxic and the most electrophilic of the α, β-unsaturated aldehydes formed during lipoperoxidation. In the present study: 1. The separation of acrolein and malondialdehyde was achieved at alkaline pH with the use of high voltage capillary electrophoresis in uncoated fused-silica capillaries. 2. It was demonstrated how the oxidation of fatty acids (arachidonic/linoleic) with ozone generates, in dose-dependent form, acrolein as one of the by-products of the lipoperoxidation process. The oxidation of open human erythrocyte membranes with ozone also generated acrolein. 3. After aldolic condensation, aldol-acrolein derivative has a positive reaction with 2-thiobarbituric acid (TBA) and shows a maximum absorption at 498 nm. This novel characteristic is used in its identification after the separation of the by-products. 4. It is possible to suggest that in the classic reaction of the denominated thiobarbituric acid reactive substances (TBARS), when used as an indicator of the degree of peroxidation in biological systems, a portion of acrolein could be present but dwarfed by the TBA-MDA adduct.
- Medina-Navarro,Mercado-Pichardo,Hernandez-Perez,Hicks
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- Pd(II)-catalyzed acetalization of terminal olefins with electron-withdrawing groups in supercritical carbon dioxide: selective control and mechanism
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Pd(II)-catalyzed acetalization of terminal olefins with electron-withdrawing groups was carried out smoothly in supercritical carbon dioxide under oxygen atmosphere when polystyrene-supported benzoquinone (PS-BQ) or CuII (CuI) chloride was employed as cocatalyst. The higher selectivity was achieved, without any chlorinated by-product detected, when using PS-BQ instead of CuII (or CuI) chloride. PS-BQ could be recycled with excellent catalytic activity remaining after each simple filtration. Chlorine ion was demonstrated to be a promoter. The different acetalization mechanisms were revealed by the subtle relationship of chlorine ion and benzoquinone (BQ) to the catalytic activity of PdCl2/PS-BQ, PdII-CuCl2 or Pd(OAc)2/PS-BQ.
- Wang, Zhao-Yang,Jiang, Huan-Feng,Ouyang, Xiao-Yue,Qi, Chao-Rong,Yang, Shao-Rong
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p. 9846 - 9854
(2007/10/03)
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- PROCESS FOR PRODUCING TETRAALKOXYPROPANE AND DERIVATIVE THEREOF
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In view of the fact that a methyl vinyl ether, which is useful as a starting material for the synthesis of tetraalkoxypropane useful as a skeleton-forming agent having a high reactivity usable as a starting material, etc. for a pharmaceutical and agrochemical intermediates such as a pyrazole derivative or pyrimidine derivative, particularly 1,1,3,3-tetramethoxypropane, is in a gaseous state and difficult to use for industrial production, tetraalkoxypropane useful as a skeleton-forming agent for a pharmaceutical and agrochemical intermediate such as a pyrazole derivative or pyrimidine derivative is easily produced on an industrial scale by using the industrially useable propoxyvinyl ether, as a starting material, without using a gaseous state methyl vinyl ether.
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Page/Page column 5
(2008/06/13)
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- Ozonolysis of 1,4-cyclohexadienes in the presence of methanol and acid. Mechanism and intermediates in the conversion of 1,4-cyclohexadiene derivatives to β-keto esters
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Conditions for the preparation of β-keto esters directly from 1,4-cyclohexadiene derivatives are described. This procedure is a further step in the application of the synthetic methodology, which consists of the combination of Birch reduction of available benzene derivatives followed by ozonolysis. In this work, the syntheses of derivatives of dimethyl γ-keto-α-aminoadipate and dimethyl β-keto glutamate from the corresponding 1,4-cyclohexadiene derivatives are described. The latter compounds are prepared from phenylalanine and phenylglycine, respectively. The study of the ozonolysis of simple alkyl derivatives of 1,4-cyclohexadiene in the presence of methanol, both in the presence and absence of acid, helped to establish the mechanism of this reaction. The proximity of the two double bonds, which are cleaved, leads to the intermediate formation of 1,2-dioxolane derivatives that could be identified by NMR spectroscopy. It is shown that regardless of the regioselectivity of the cleavage of the primary ozonide, which is formed, all 1,2-dioxolane derivatives can lead to β-keto esters. This is due to the equilibrium between these dioxolanes in the presence of methanol and acid.
- Gbara-Haj-Yahia, Isra,Zvilichovsky, Gury,Seri, Noa
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p. 4135 - 4139
(2007/10/03)
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- Process for the preparation of malondialdehyde-derivatives
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Process for the preparation of malondialdehyde-derivatives by reacting vinylesters with orthoesters in the presence of a precious metal catalyst.
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- Process for preparing acetals of malondialdehyde
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A process directed to the preparation of acetals of malondialdehyde by reacting alkylvinyl ethers or esters with ortho formates in the gas phase with a heterogeneous catalyst.
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Page column 5-6
(2008/06/13)
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- Difunctional and Hetercyclic Prducts from the Ozonolysis of Conjugated C5-C8 Cyclodienes
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Ozonolyses of the conjugated C5-C8 cyclodienes 1a-d in methanol, followed by reduction with DMS, have been examined.Monoozonolyses gave the corresponding unsaturated dialdehydes 2e as the primary products.In subsequent reactions, the dialdehydes 2e derived from the monoozonolyses of 1a, 1b, and 1c gave in high yields the heterocyclic compounds 7, 8k, and 9k, respectively.Diozonolyses of 1a-d gave the corresponding dialdehydes 3e as the primary products.In subsequent reactions, the dialdehydes 3e derived from 1b and 1c gave the heterocyclic compounds 8l and 9l, respectively.In addition, aldehydes 2e and 3e undervent partial acetalization reactions with methanol.
- Griesbaum, Karl,Jung, In Chang,Mertens, Henri
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p. 6024 - 6027
(2007/10/02)
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- Ozonolyse von Olefinen, III: Saeurekatalysierte Ozonolyse von 3-Hexen-1,6- und 2-Penten-1,5-dicarbonylderivaten
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The ozonolysis of mono-unsaturated compounds containing the structural element =CH-CH2-R was investigated.Reductive ozonolysis of (E)-3-hexene-1,6-dioic acid gives methyl 3,3-dimethoxypropanoate (2), whereas ozonolysis of dimethyl (E)-3-hexene-1,6-dioate (1a) and (Z)-1,1,6,6-tetramethoxy-3-hexene (1b) in a methanolic solution of HCl leads to a mixture of 2, dimethyl malonate (3a) and 1,1,3,3-tetramethoxypropane (3b).The homologuos derivatives, dimethyl glutaconate (4a) and 1,1,5,5-tetramethoxy-2-pentene (4b), were ozonized to give mixtures of 2, 3, dimethyl oxalate (5), methyl 2,2-dimethoxyacetate (6a), and 1,1,2,2-tetramethoxyethane (6b).The ratios of the various reaction products were determined by gas chromatography.In each case the formation of the bifunctional derivatives 2 and 6a was favoured.
- Poklukar, Norbert,Mittelbach, Martin
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p. 203 - 207
(2007/10/02)
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- Ozonolysis of Olefins, I. - Ozonolysis of 1,4-Cyclohexadiene and Acid-Catalysed Reaction of Primary Cleavage Products
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The reaction of 1,4-cyclohexadiene (1) with ozone under different reaction conditions was investigated.Complete ozonolysis of 1 in chloroform led to a highly explosive ozonide.Oxidative ozonolysis gave malonic acid in 30percent yield, ozonolysis in alcoholic solutions of HCl gave alkyl 3,3-dialkoxypropionates 3 in 60-70percent yield and small amounts of the 1,1,3,3-tetraalkoxypropane 4 as well as dialkyl malonate 5.Partial ozonolysis of1 in HCl/methanol led to a mixture of 3,5 and the corresponding (Z)-3-hexene derivatives 6a-c.Depending on the reaction time and concentration of HCl, also the two methanol addition products 7b and 7d could be obtained.To verify the structure of these two compounds, 4-methoxycyclohexene (8) was ozonized in HCl/methanol, which gave a mixture of 7a-d.
- Mittelbach, Martin,Poklukar, Norbert,Junek, Hans
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p. 185 - 188
(2007/10/02)
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- Relative Reactivities of Acetals and Orthoesters in Lewis Acid Catalyzed Reactions with Vinyl Ethers. A Systematic Investigation of the Synthetic Potential of Acetals and Orthoesters in Electrophilic Alkoxyalkylations of Enol Ethers
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The relative reactivities of acetals and orthoesters in BF3OEt2-catalyzed reactions with methyl vinyl ether (-78 deg C, CH2Cl2) have been determined by competition experiments.A reactivity increase by 5 orders of magnitude was found in the series: saturated acetals rel values of the para-substituted benzaldehyde acetals follow a Hammett ? correlation (ρ = -4.6).Whereas the krel values of the aldehyde acetals are correlated with the corresponding rate constants of acid-catalyzed hydrolyses, ketals and orthoesters devaite from this correlation.It is concluded that the krel listing in Scheme II can be used to predict the results of Lewis acid catalyzed additions of acetals and orthoesters toward vinyl ethers: The formation of 1:1 addition products may only be expected, if the relevant functional group of the reactants is listed below the functional group of the potential 1:1 products.
- Brueggen, Uwe von der,Lammers, Roswitha,Mayr, Herbert
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p. 2920 - 2925
(2007/10/02)
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- CONDENSATION OF o-PHENYLENE DIAMINE AND SUBSTITUTED ACROLEINS TO FORM MACROHETEROCYCLES
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The reaction of o-phenylene diamine with β-alkoxy-, β-dimethylamino-, and β-acetoxy-α-alkyl- or α-arylacroleins has been studied.A new synthesis of 7,16-diaryldihydrodibenzo-tetraazaannulenes was developed, and the syntheses of 5,14 dihydrodibenzoteraazaannulene and 7,16-dialkyldihydrodibenzotetraazaannulenes were improved. 5,14-Dihydrodibenzotetraazaannulenes were synthesized with various substituents in the benzene rings and at possitions 7 an 16.
- Yatluk, Yu. G.,Suvorov, A. L.
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p. 316 - 320
(2007/10/02)
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