- Model studies on the pattern of volatiles generated in mixtures of amino acids, lipid-oxidation-derived aldehydes, and glucose
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The development of flavor and browning in thermally treated foods results mainly from the Maillard reaction and lipid degradation but also from the interactions between both reaction pathways. To study these interactions, we analyzed the volatile compounds resulting from model reactions of lysine or glycine with aldehydes originating from lipid oxidation [hexanal, (E)-2-hexenal, or (2E,4E)-decadienal] in the presence and absence of glucose. The main reaction products identified in these model mixtures were carbonyl compounds, resulting essentially from amino-acid-catalyzed aldol condensation reactions. Several 2-alkylfurans were detected as well. Only a few azaheterocyclic compounds were identified, in particular 5-butyl-2-propylpyridine from (E)-2-hexenal model systems and 2-pentylpyridine from (2E,4E)-decadienal model reactions. Although few reaction products were found resulting from the condensation of an amino acid with a lipid-derived aldehyde, the amino acid plays an important role in catalyzing the degradation and further reaction of these carbonyl compounds. These results suggest that amino-acid-induced degradations and further reactions of lipid oxidation products may be of considerable importance in thermally processed foods.
- Adams, An,Kitryte, Vaida,Venskutonis, Rimantas,De Kimpe, Norbert
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experimental part
p. 1449 - 1456
(2011/10/05)
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- One-pot synthesis of C8 aldehydes/alcohols from propylene using eco-friendly hydrotalcite supported HRhCO(PPh3)3 catalyst
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A multi-functional catalyst [HF/HT] containing a rhodium complex, HRh(CO)(PPh3)3 [HF] and a solid base, hydrotalcite Mg 1-xAlx(OH2)x+(CO 32-)x/n·mH2O [HT], synthesized by impregnation of [HF] onto the surface of [HT], was investigated for the one-pot synthesis of C8 aldol derivatives (aldehydes or alcohols) from propylene. The catalyst was found to be efficient to carry out hydroformylation, aldol condensation and hydrogenation reactions in one pot. The catalytic activity of [HF/HT(X)] was studied in detail as functions of Mg/Al molar ratio (X) of [HT], amount of [HF] complex and [HT], and reaction temperature. The selectivity for 2-ethylhexanal was observed to increase upon increasing X and amount of [HT]. The highest selectivity for 2-ethylhexanol was observed for [HT] Mg/Al molar ratio of 3.5 at 250°C. The kinetic profiles of the various products obtained were in agreement with the reaction pathway proposed to understand the role of the [HF/HT] catalyst on the formation of C8 aldol derivatives. Thermal stability of the [HF/HT] catalyst system was also investigated. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Sharma, Sumeet K.,Srivastava, Vivek K.,Shukla, Ram S.,Parikh, Parimal A.,Jasra, Raksh V.
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p. 277 - 286
(2008/02/02)
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- Process for preparing aldol derivatives from alkenes using catalyst
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The present invention provides a novel eco-friendly multi-functional catalyst system useful to obtain C2(n+1) aldol-derivative from Cn-alkenes where n ranges from 2 to 10 in a single step under hydroformylation reaction conditions and adol formation conditions.
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Page/Page column 6-11
(2008/06/13)
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- Aldol Reaction and Robinson-Type Annelation Catalyzed by Lanthanoid Triisopropoxides
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Lanthanoid triisopropoxides are active catalysts for aldol reactions.Aldehydes give the corresponding β-hydroxyaldehydes at low temperatures in good yields, whereas ketones are less reactive, but form condensation products at high temperatures.Exceptionally, γ- or δ-diketones easily undergo condensation to give five- and six-membered unsaturated ketones in high yields.The lanthanoid propoxides, catalyzing the Michael addition of ketones to α,β-unsaturated ketones, which give δ-diketones, are also good catalysts for the Robinson-type annelation.In these reactions, the catalytic activity of the lanthanum propoxide is higher than those of the heavy lanthanoid propoxides, and is almost comparable to that of sodium isopropoxide.Since aluminum triisopropoxide shows poor activity, the lanthanoid propoxides are considerably basic for trivalent metal alkoxides.
- Okano, Tamon,Satou, Yoshikazu,Tamura, Motoshi,Kiji, Jitsuo
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p. 1879 - 1886
(2007/10/03)
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- Transformations of butyraldehyde in the presence of catalysts based on large-pore molecular sieves VPI-5 and AlPO4-8
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It was found that zeolite-like ctystalline aluminophosphates VPI-5, Si-VPI-5, and Mn-VPI-5 as well as those derived from them, AlPO4-8, SAPO4-8, and MnAPO4-8, are capable of catalyzing aldol condensation and crotonization of butyraldehyde (BA).Pd/AlPO4-8 is catalytically active in hydrocondensation of BA with H2 at atmospheric pressure.The activities in BA conversion to 2-ethylhexane-3-ol-1-al increase in following order: Mn-VPI-5 +NaX (CsNaX), but they are much more stable.Pd/AlPO4-8 catalyzes BA conversion to 2-ethylhexanal even in the absence of H2 feed to the reaction zone.The influence of catalyst pretreatments and experimental conditions on the catalyst structures and catalytic activities is discussed. - Key words: butyraldehyde; condendation; crystalline aluminophosphates; molecular sieves; VPI-5; AlPO4-8; catalysis.
- Isakov, Ya. I.,Minachev, Kh. M.,Tome, R.,Tissler, A.,Oehlmann, G.,et al.
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p. 2004 - 2010
(2007/10/02)
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- Self-Condensation of n-Butyraldehyde over Solid Base Catalysts
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The catalytic properties of various solid bases for self-condensation of n-butyraldehyde in liquid phase were studied to elucidation the factors governing the activity and selectivity.For alkaline earth oxide catalysts and γ-alumina catalyst, aldol condensation ocurred, followed by Tishchenko-type cross-esterification of n-butyraldehyde with the dimer produced by the aldol condensation to form trimeric glycol ester.Alkali ion-modified alumina catalysts exhibited a high selectivity for the aldol condensation dimer, the trimeric glycol ester being formed little.Both basic and acidic sites on the surfaces of the alkaline earth oxides and γ-alumina were assumed to contribute to Tishchenko-type cross-esterification.The suppression of Tischenko-type cross-esterification.The suppression of Tischenko-type cross-esterification for alkali ion-modified alumina catalysts is due to the absence of acidic sites on the surfaces.The catalytic performances of alumina-supported magnesium oxide exhibited lower activity but higher selectivity to trimeric glycol ester than MgO.This catalytic feature was caused by the lower basicity and higher acidity on the surface of alumina-supported magnesium oxide as compared with MgO.The activity of alkali ion-exchanged zeolites was lowest among the catalysts examined in this study.The modification of zeolites with excess alkali ions improved the activity.
- Tsuji, Hideto,Yagi, Fuyuki,Hattori, Hideshi,Kita, Hideaki
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p. 759 - 770
(2007/10/02)
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- Asymmetric synthesis of sulfinimines: Chiral ammonia imine synthons
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Two Andersen-type procedures for the preparation of enantiopure sulfinimines 1 (R=H) in better than 95% ee from nitriles and aldehydes are described.
- Davis, Franklin A.,Reddy, Rajarathnam E.,Szewczyk, Joanna M.,Portonovo, Padma S.
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p. 6229 - 6232
(2007/10/02)
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- Studies on the Oxidation of Enamines with Molecular Oxygen. I. Oxidation of Some Piperidino Alkenes
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In the autoxidation of 1-piperidinocyclohex-1-ene (1), 1-piperidinobut-1-ene (2), 3-piperidinopent-2-ene (3), and 1-piperidino-2-methyl-prop-1-ene (4) only products of an oxidative attack at the C=C-double bond are formed.Both α-aminoketones, the products of the rearrangement of primarily formed epoxides, and products of the oxidative scission of the C=C double bond are obtained.As a side reaction some hydrolysis of the starting enamines takes place.This hydrolysis proves that some water must be formed during the enamine oxidation.
- Blau, Karla,Voerckel, V.
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p. 285 - 292
(2007/10/02)
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- Stereochemistry in the Knoevenagel Reaction of Methyl Arylsulphinylacetate and Aldehydes
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The stereochemistry of the mechanism of the amine-catalyzed Knoevenagel reaction has been studied.Simple treatment of methyl arylsulphinylacetate (1) and aldehydes (2) with a catalytic amount of a secondary amine produced thermodynamically stable E-alkene
- Tanikaga, Rikuhei,Konya, Naoto,Tamura, Tadashi,Kaji, Aritsune
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p. 825 - 830
(2007/10/02)
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- MECHANISM OF THE ALDOL CONDENSATION OF ALDEHYDES, CATALYZED BY THE SALTS OF METALS AND HIGHER ORGANIC ACIDS
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The salts of transition metals are the most active catalysts for the aldol condensation of aliphatic aldehydes.By IR spectroscopy it was found that an intermediate complex between the aldehyde and the catalyst is formed at the initial stage of the reaction.A chelate mechanism of catalysis is proposed for the aldol condensation and satisfactorily explains the order of formation of the intermediate and final products.
- Katsnel'son, M. G.,Kagna, S. Sh.,Nikitina, L. I.,Oranskaya, O. M.,Semenskaya, I. V.
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p. 1437 - 1441
(2007/10/02)
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- Base-Induced Fragmentation of β-Hydroxy Nitrosamines
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β-Hydroxy nitrosamines have been found to undergo a base-induced fragmentation reaction.The reaction cleaves the Cα-Cβ bond of the substrate to produce an aldehyde or ketone and a smaller alkylnitrosamine.Rate contants for the fragmentation induced by potassium tert-butoxide in THF or tert-butyl alcohol have been measured for nine substrates at temperatures between 35 and 70 deg C.The rate constants are a function of base concentration and range between 0.15x10-6 and 308x10-6 s-1.Rate constants have been determined for (2-hydroxyethyl)methylnitrosamine,N-nitrosodiethanolamine, (2-hydroxy-2-methylpropyl)methylnitrosamine, (2-hydroxy-2-phenylethyl)methylnitrosamine, N-nitrosoephedrine, (2-hydroxy-2,2-diphenylethyl)methylnitrosamine, and (2-hydroxy-2-phenylpropyl)methylnitrosamine.The nitrosamino alcohol fragmentation rates are in the order tertiary > secondary > primary, and the rate appears to be a function of product stability and steric strain in the substrate.A mechanism which accounts for these observations is proposed.
- Loeppky, R. N.,McKinley, W. A.,Hazlitt, L. G.,Outram, J. R.
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p. 4833 - 4841
(2007/10/02)
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