- Cassis and Green Tea: Spontaneous Release of Natural Aroma Compounds from β-Alkylthioalkanones
-
In depth headspace analysis of the slow degradation of β-alkylthioalkanones in ambient air led to the discovery of a novel δ-cleavage pathway, by which β-mercaptoketones are released. Since β-mercaptoketones are potent natural aroma compounds occurring in many fruits, herbs and flowers, the discovery of an enzyme-independent molecular precursor for this class of high-impact molecules is of practical importance. Moreover, the formation of β-diketones and aldehydes by concomitant oxidation at the α-sulfur-position enhances the versatility of this class of aroma precursors. A mechanistic model is proposed which suggests that the oxidative degradation occurs through a novel Pummerer-type rearrangement of initially formed persulfoxides.
- B?ttig, Sarah,Bochet, Christian G.,Egger, Timothy,Flachsmann, Felix,Gey, Olga
-
-
- Ketone Formation from Carboxylic Acids by Ketonic Decarboxylation: The Exceptional Case of the Tertiary Carboxylic Acids
-
For the reaction mechanism of the ketonic decarboxylation of two carboxylic acids, a β-keto acid is favored as key intermediate in many experimental and theoretical studies. Hydrogen atoms in the α-position are an indispensable requirement for the substrates to react by following this mechanism. However, isolated observations with tertiary carboxylic acids are not consistent with it and these are revisited and discussed herein. The experimental results obtained with pivalic acid indicate that the ketonic decarboxylation does not occur with this substrate. Instead, it is consumed in alternative reactions such as disintegration into isobutene, carbon monoxide, and water (retro-Koch reaction). In addition, the carboxylic acid is isomerized or loses carbon atoms, which converts the tertiary carboxylic acid into carboxylic acids bearing α-proton atoms. Hence, the latter are suitable to react through the β-keto acid pathway. A second substrate, 2,2,5,5-tetramethyladipic acid, reacted by following the same retro-Koch pathway. The primary product was the monocarboxylic acid 2,2,5-trimethyl-4-hexenoic acid (and its double bond isomer), which might be further transformed into a cyclic enone or a lactone. The ketonic decarboxylation product, 2,2,5,5-tetramethylcyclopentanone was observed in traces (0.2 % yield). Therefore, it can be concluded that the observed experimental results further support the proposed mechanism for the ketonic decarboxylation via the β-keto acid intermediate.
- Oliver-Tomas, Borja,Renz, Michael,Corma, Avelino
-
p. 12900 - 12908
(2017/09/25)
-
- A structure/catalytic activity study of gold(i)-NHC complexes, as well as their recyclability and reusability, in the hydration of alkynes in aqueous medium
-
We conducted a structure/catalytic activity study of water-soluble gold(i) complexes-supporting sulfonated NHC ligands-in the hydration of alkynes in pure water or water nsp;:nsp;methanol (1nsp;:nsp;1), as well as their recyclability. Comparative studies were carried out with the addition of different silver salts. Our results indicate that the bulkier complex is the most effective and that the addition of methanol as co-solvent not only shortens reaction times but also stabilizes the less bulky complexes.
- Fernández, Gabriela A.,Chopa, Alicia B.,Silbestri, Gustavo F.
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p. 1921 - 1929
(2016/04/05)
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- Hydroxyketones in the thiadiazine cycle formation
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Cyclocondensation of 1-hydroxyketones with thiosemicarbazide resulted in thiadiazines. Nitrate ester of 1-hydroxyketone reacted under similar conditions to give the corresponding thiosemicarbazone. In the case of bromoacetyl-substituted nitrate ester of 1-hydroxyketone, condensation proceeded via intramolecular reaction between the thiol and bromomethyl groups.
- Pulatov, E. Kh.,Isobaev,Mavlonov
-
p. 2475 - 2478
(2017/05/10)
-
- A mild method for the replacement of a hydroxyl group by halogen. 1. Scope and chemoselectivity
-
α-Chloro-, bromo- and iodoenamines, which are readily prepared from the corresponding isobutyramides have been found to be excellent reagents for the transformation of a wide variety of alcohols or carboxylic acids into the corresponding halides. Yields are high and conditions are very mild thus allowing for the presence of sensitive functional groups. The reagents can be easily tuned allowing therefore the selective monohalogenation of polyhydroxylated molecules. The scope and chemoselectivity of the reactions have been studied and reaction mechanisms have been proposed.
- Munyemana, Fran?ois,George, Isabelle,Devos, Alain,Colens, Alain,Badarau, Eduard,Frisque-Hesbain, Anne-Marie,Loudet, Aurore,Differding, Edmond,Damien, Jean-Marie,Rémion, Jeanine,Van Uytbergen, Jacqueline,Ghosez, Léon
-
p. 420 - 430
(2015/12/31)
-
- 3-methyl-3-penten-2-one preparation method
-
The invention relates to a preparation method of 3-methyl-3-amylene-2-ketone. The preparation method comprises the steps of mixing butanone and a solid acid catalyst at 0-80 DEG C, adding acetaldehyde, fully mixing, reacting continuously, separating and purifying after reaction to obtain the 3-methyl-3-amylene-2-ketone, wherein the solid acid catalyst is highly-acidic dry type sulfonic acid group based polystyrene with H or sulfonic acid group based perfluorination cation exchange resin. According to the method, the solid acid catalyst is adopted, compared with the traditional synthetic method that strong acid and strong base are used, the method can greatly reduce the follow-up separation difficulty and environment pollution degree, no equipment corrosion is caused, and the product yield and the purity are high, therefore, the preparation method of 3-methyl-3-amylene-2-ketone is green and environment-friendly; and besides, no assisted solvent is adopted, the follow-up separation difficulty is reduced, the energy consumption and the production cost are low, and the industrial reliability is strong.
- -
-
Paragraph 0019-0021
(2016/10/24)
-
- Aluminum oxide-induced gas-phase ring-opening in methyl substituted gem-difluorocyclopropanes, leading to 2-fluorobuta-1,3-dienes and vinylacetylenes
-
A gas-phase pyrolysis of methyl-substituted gem-difluorocyclopropanes in a flow-tube reactor in the presence of Al2O3 at 185 - 250 °C gives 2-fluorobuta-1,3-dienes and vinylacetylenes.
- Volchkov,Lipkind,Novikov,Nefedov
-
p. 658 - 663
(2015/11/27)
-
- Reactions of a tungsten-germylyne complex with α,β-unsaturated ketones: Complete cleavage of the W/Ge bond and formation of two types of η3-germoxyallyl tungsten complexes
-
Germylyne complex Cp(CO)2W/Ge{C(SiMe3)3} (1) reacted with two molecules of RC(O)CH=CH2 (R = Me, Et) to give η3-allyl complexes, in which an oxagermacyclopentene framework was bound to an η3-allyl ligand through an oxygen atom. In the reaction with α-Me-substituted MeC(O)C(Me)=CH2, 1 reacted with only one molecule of the substrate to give another type of η3- allyl complex, in which a five-membered oxagermacyclopentenyl ring was coordinated to the W center in an η3 fashion. Both reactions resulted in unprecedented complete cleavage of a W/Ge triple bond.
- Fukuda, Tetsuya,Hashimoto, Hisako,Tobita, Hiromi
-
supporting information
p. 80 - 83
(2014/01/23)
-
- Silica-supported HgSO4/H2SO4: A convenient reagent for the hydration of alkynes under mild conditions
-
The silica-supported aqueous-phase catalyst (SAPC) approach has proven convenient for efficiently performing the hydration of alkynes with HgSO 4/H2SO4 to give the corresponding carbonyl compounds in dichloromethane under mild conditions. The use of this solid reagent significantly improves the reaction work-up as it merely involves filtering and evaporating the solvent.
- Mello, Rossella,Alcalde-Aragonés, Ana,González-Nú?ez, María Elena
-
scheme or table
p. 4281 - 4283
(2010/09/07)
-
- Isolable gold(I) complexes having one low-coordinating ligand as catalysts for the selective hydration of substituted alkynes at room temperature without acidic promoters
-
Hydration of a wide range of alkynes to the corresponding ketones has been afforded in high yields at room temperature by using gold(I)-phosphine complexes as catalyst, with no acidic cocatalysts required. Suitable substrates covering alkyl and aryl terminal alkynes, enynes, internal alkynes, and propargylic alcohols, including enantiopure forms, are cleanly transformed to the corresponding ketones in nearly quantitative yields. Acid-labile groups present in the substrates are preserved. The catalytic activity strongly depends on both the nature of the phosphine coordinated to the gold (I) center and the softness of the counteranion, the complex AuSPhOsNTf2 showing the better activity. A plausible mechanism for the hydration of alkynes through ketal intermediates is proposed on the basis of kinetic studies. The described catalytic system should provide an efficient alternative to mercury-based methodologies and be useful in synthetic programs.
- Leyva, Antonio,Corma, Avelino
-
scheme or table
p. 2067 - 2074
(2009/08/07)
-
- Effect of additives on chemoselectivity and diastereoselectivity in the catalytic epoxidation of chiral allylic alcohols with hydrogen peroxide and binuclear manganese complexes
-
The catalytic oxidations of chiral allylic alcohols 2 by manganese complexes of the cyclic triamine 1,4,7-trimethyl-1,4,7-triazacyclononane (tmtacn) 1 and hydrogen peroxide as oxygen donor in the presence of co-catalyst are investigated to understand the
- Kilic, Hamdullah,Adam, Waldemar,Alsters, Paul L.
-
experimental part
p. 1135 - 1140
(2009/07/04)
-
- Synthesis and characterization of solid acid in system SnO 2/B2O3
-
SnO2/B2O3 materials with Sn/B molar ratio 1:1; 1:2 and 1:3 were synthesized from SnCl4, H3BO 3 and (NH2)2CO. The samples contain SnO 2 with different cristallinity and an amorphous borate phase. Their thermal transformations were investigated by DTA method. The surface acidity was investigated by TPR method using conversion of 2-methyl-3-butyn-2-ol (MBOH). The temperature maximum of MBOH dehydration for SnO2/B 2O3 materials is close to that for ZrO2/ SiO2 catalyst. On the surface of SnO2/B2O 3 mainly strong acid sites were detected. In the case of B 2O3/SiO2 (aerosil), samples have mainly weak acid sites. The surface of pure SnO2 has amphoteric sites. IR spectroscopy and MAS NMR spectra of 11B showed that SnO 2/B2O3 materials had three-and four-coordinated B atoms.
- Viter,Nagorny
-
experimental part
p. 2081 - 2087
(2009/04/11)
-
- Ruthenium-lewis acid catalyzed asymmetric diels-alder reactions between dienes and α,β-unsaturated ketones
-
The complex [Ru(Cp)(R,R-BIPHOP-F)(acetone)][SbF6],(R,R)-1a. was used as catalyst for asymmetric Diels-Alder reactions between dienes (cyclopentadiene, methylcyclopentadienc, isoprene, 2,3-dimethylbutadiene) and α,β-unsaturated ketones (methyl vinyl ketone (MVK). ethyl vinyl ketone, divinyl ketone, α-bromovinyl methyl ketone and α-chlorovinyl methyl ketone). The cycloaddition products were obtained in yields of 50-_90% and with enantioselectivities up to 96% ee. Ethyl vinyl ketone, divinyl ketone and the halogenated vinyl ketones worked best and their reactions with acyclic dienes consistently provided products with >90% ee. α-Chlorovinyl methyl ketone performed better than α-bromovinyl methyl ketone. The reaction also provided a [4.3.1]bicyclic ring system in 95% ee through an intramolecular cycloaddition reaction. Crystal structure determinations of [Ru(Cp)((S,S)-BIPHOP-F)(mvk)]-[SbF6], (S,S)-1b, and [Ru(Cp)((R,R)-Me4BIPHOP-F)(acrolein)][SbF6], (R,R)-2b, provided the basis for a rationalization of the asymmetric induction.
- Rickerby, Jenny,Vallet, Martial,Bernardinelli, Gerald,Viton, Florian,Kuendig, E. Peter
-
p. 3354 - 3368
(2008/03/27)
-
- Catalyst and process for the preparation of unsymmetrical ketones
-
Carboxylic acid mixtures form unsymmetrical ketones in yields approaching statistical using zirconia catalysts promoted with Group IA and IIA elements. Active catalysts exist in their monoclinic or tetragonal but not cubic form. And the level of promoter loading is generally less than ten percent. The advantages of this catalyst over other ketonization catalysts include its high selectivity to ketones, its low formation of dehydrogenated byproducts, and its stability. The catalyst stability permits its regeneration to remove carbon accumulations by air oxidation. This regeneration restores full catalytic activity.
- -
-
Page/Page column 7
(2008/06/13)
-
- IMIDAZO-TRIAZINE DERIVATIVES AS LIGANDS FOR GABA RECEPTORS
-
A class of 7-phenylimidazo[1,2-b][1,2,4]triazine derivatives, substituted at the meta position of the phenyl ring by an optionally substituted aryl or heteroaryl group which is directly attached or bridged by an oxygen atom or a -NH- linkage, and substituted on the phenyl ring by one or two further substituents as defined herein, being selective ligands for GABAA receptors, in particular having good affinity for the α2 and/or α3 and/or α5 subunit thereof, are accordingly of benefit in the treatment and/or prevention of adverse conditions of the central nervous system, including anxiety, convulsions and cognitive disorders.
- -
-
Page/Page column 41
(2010/02/07)
-
- Chiral hydroperoxides as oxygen source in the catalytic stereoselective epoxidation of allylic alcohols by sandwich-type polyoxometalates: Control of enantioselectivity through a metal-coordinated template
-
The epoxidation of allylic alcohols is shown to be efficiently and selectively catalyzed by the oxidatively resistant sandwich-type polyoxometalates, POMs, namely [WZnM2(ZnW9O 34)2]q- [M = OV(IV), Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], with organic hydroperoxides as oxygen source. Conspicuous is the fact that the nature of the transition metal M in the central ring of polyoxometalate affects significantly the reactivity, chemoselectivity, regioselectivity, and stereoselectivity of the allylic alcohol epoxidation. For the first time, it is demonstrated that the oxovanadium(IV)-substituted POM, namely [ZnW(VO)2(ZnW 9O34)2]12-, is a highly chemoselective, regioselective, and also stereoselective catalyst for the clean epoxidation of allylic alcohols. A high enantioselectivity (er values up to 95:5) has been achieved with [ZnW(VO)2(ZnW9O 34)2]12- and the sterically demanding TADOOL-derived hydroperoxide TADOOH as regenerative chiral oxygen source. Thus, a POM-catalyzed asymmetric epoxidation of excellent catalytic efficiency (up to 42 000 TON) has been made available for the development of sustainable oxidation processes. The high reactivity and selectivity of this unprecedented oxygen-transfer process are mechanistically rationalized in terms of a peroxy-type vanadium(V) template.
- Adam, Waldemar,Alsters, Paul L.,Neumann, Ronny,Saha-Moeller, Chantu R.,Seebach, Dieter,Beck, Albert K.,Zhang, Rui
-
p. 8222 - 8231
(2007/10/03)
-
- A highly chemoselective, diastereoselective, and regioselective epoxidation of chiral allylic alcohols with hydrogen peroxide, catalyzed by sandwich-type polyoxometalates: Enhancement of reactivity and control of selectivity by the hydroxy group through metal-alcoholate bonding
-
Sandwich-type polyoxometalates (POMs), namely [VZnM2(ZnW9O34)2]q- [M = Mn(II), Ru(III), Fe(III), Pd(II), Pt(II), Zn(II); q = 10-12], are shown to catalyze selectively the epoxidation of chiral allylic alcohols with 30% hydrogen peroxide under mild conditions (ca. 20 °C) in an aqueous/organic biphasic system. The transition metals M in the central ring of polyoxometalate do not affect the reactivity, chemoselectivity, or stereoselectivity of the allylic alcohol epoxidation by hydrogen peroxide. Similar selectivities, albeit in significantly lower product yields, are observed for the lacunary Keggin POM [PW11O39]7-, in which a peroxotungstate complex has been shown to be the active oxidizing species. All these features support a tungsten peroxo complex rather than a high-valent transition-metal oxo species operates as the key intermediate in the sandwich-type POM-catalyzed epoxidations. On capping of the hydroxy functionality through acetylation or methylation, no reactivity of these hydroxy-protected substrates [1a(Ac) and 1a(Me)] is observed by these POMs. A template is proposed to account for the marked enhancement of reactivity and selectivity, in which the allylic alcohol is ligated through metal - alcoholate bonding, and the H2O2 oxygen source is activated in the form of a peroxotungsten complex. 1,3-Allylic strain promotes a high preference for the threo diastereomer and 1,2-allylic strain a high preference for the erythro diastereomer, whereas tungsten - alcoholate bonding furnishes high regioselectivity for the epoxidation of the allylic double bond. The estimated dihedral angle α of 50 - 70° for the metal - alcoholate-bonded template of the POM/H2O2 system provides the best compromise between 1,2A and 1,3A strain during the oxygen transfer. In contrast to acyclic allylic alcohols 1, the M-POM-catalyzed oxidation of the cyclic allylic alcohols 4 by H2O2 gives significant amounts of enone.
- Adam, Waldemar,Alsters, Paul L.,Neumann, Ronny,Saha-Moeller, Chantu R.,Sloboda-Rozner, Dorit,Zhang, Rui
-
p. 1721 - 1728
(2007/10/03)
-
- Fine particle and gaseous emission rates from residential wood combustion
-
Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning-communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter(a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and se mivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8- C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and forts were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography. Residential wood combustion emissions were analyzed to determine emission rates and to develop chemical emissions profiles that represent the appliances and woods typically used in wood-burning communities. Over 350 elements, inorganic compounds, and organic compounds were quantified. A range of 4-9 g/kg dry fuel of particulate matter (a dilution stack sampler equipped with a 2.5-μm particle selective cyclone. Emissions were diluted 20-70 times, cooled to ambient temperature, and allowed 80 s for condensation prior to collection. Wood type, wood moisture, burn rate, and fuel load were varied for different experiments. Fine particle and semivolatile organic compounds were collected on filter/PUF/XAD/PUF cartridges. Inorganic samples and mass were collected on Teflon and quartz filters. Volatile organic carbon compounds were trapped with Tenax (C8-C20), canister (C2-C12), and 2,4-dinitrophenylhydrazine impregnated cartridges (carbonyl compounds). Analysis of particle and semivolatile organic species was conducted by gas chromatography/mass spectrometry. Teflon filters were analyzed for mass by gravimetry, trace elements were analyzed by X-ray fluorescence, and ammonium was analyzed by automated colorimetry. Quartz filters were analyzed for organic and elemental carbon by thermal/optical reflectance, and ions were analyzed by ion chromatography. Select quartz filters were analyzed by accelerator mass spectrometry for carbon-12 and carbon-14 abundance. Canister and Tenax samples were analyzed by gas chromatography with a flame ionization detector, and carbonyl compounds were analyzed by high-performance liquid chromatography.
- Mcdonald, Jacob D.,Zielinska, Barbara,Fujita, Eric M.,Sagebiel, John C.,Chow, Judith C.,Watson, John G.
-
p. 2080 - 2091
(2007/10/03)
-
- Chemoselective C-H oxidation of alcohols to carbonyl compounds with iodosobenzene catalyzed by (Salen)chromium complex
-
Primary and secondary alcohols with benzylically and allylically activated C-H bonds are chemoselectively oxidized to the corresponding carbonyl compounds by the (salen)Cr(III) complex I as the catalyst and iodosobenzene as the oxygen source; the oxidizing species is the Cr(V) oxo complex. Allylic alcohols with fully substituted double bonds give appreciable amounts of epoxides besides the C-H oxidation products enones, while saturated alcohols are less readily oxidized.
- Adam, Waldemar,Gelalcha, Feyissa Gadissa,Saha-Moeller, Chantu R.,Stegmann, Veit R.
-
p. 1915 - 1918
(2007/10/03)
-
- Synthesis and characterization of ZrO2 as acid-basic catalysts: Reactivity of 2-methyl-3-butyn-2-ol
-
Two ZrO2-based catalysts have been synthesized by thermal treatment of a gel prepared from ZrOCl2 · 8H2O. The effect of different preparation parameters on the final properties of the solids was studied. Textural characterization was carried out from nitrogen adsorption/desorption isotherms. XRD and FT-Raman spectroscopy have been used to elucidate the physical state of the catalysts. Their acid-base properties were studied following temperature programmed desorption-mass spectrometry and diffuse reflectance infrared Fourier transform techniques, by using pyridine, 2,6-dimethylpyridine and carbon dioxide as probe molecules. Both solids were tested for the 2-methyl-3-butyn-2-ol reaction by using two different procedures: (a) in a microcatalytic pulse reactor and (b) through isotherm and temperature programmed surface reactions in a flow reactor. In addition, temperature programmed oxidation and temperature programmed desorption experiments revealed that catalyst deactivation was caused by carbon deposition on the catalytic surface. Amphoteric selectivity for both solids, leading to 3-hydroxy-3-methyl-2-butanone and 3-methyl-3-buten-2-one, depends on the reaction temperature; thus, it is 92% at 225°C for a catalyst calcined at 400°C (ZrO2-400VAC).
- Aramendia, M. Angeles,Borau, Victoriano,Jimenez, Cesar,Marinas, Jose M.,Marinas, Alberto,Porras, Andres,Urbano, Francisco J.
-
p. 240 - 250
(2007/10/03)
-
- Structure, texture, acidity and catalytic performance of AlPO4-caesium oxide catalysts in 2-methyl-3-butyn-2-ol conversion
-
A series of aluminium orthophosphate-caesium oxide systems with various caesium oxide loadings (5-30 wt%) were prepared by impregnation of ALPO4 with a methanolic solution of caesium acetate and characterized by TG/DTA, XRD, DRIFT, Raman, SEM-EDX, XPS, 27Al and 31P MAS NMR and nitrogen adsorption. Aluminium orthophosphate remained amorphous with caesium oxide incorporation when calcined at 873 K for 3 h. After thermal treatment at 1423 K it crystallized in the tridymite form except for materials containing 30 wt% caesium oxide. DRIFT spectroscopy showed that the P-OH stretching vibration at 3670 cm-1 decreased in intensity with caesium oxide loading. Materials at 20-30 wt% caesium oxide did not exhibit any hydroxyl bands. Besides, Al and P atoms remained in tetrahedral coordination as in unmodified aluminium orthophosphate. Moreover, the incorporation of caesium oxide leads, simultaneously, to a progressive decrease in surface area and pore volume (larger at 30 wt% caesium oxide) as well as to an increase in the most frequently occurring pore radius. On the other hand, caesium oxide reduced both the number and strength of acid sites as the caesium content increased. Consequently, 2-methylbut-3-yn-2-ol (MBOH) underwent almost exclusively dehydration to 3-methyl-3-buten-1-yne (acid activity) on pure AlPO4, whereas its modification with increasing amounts of caesium oxide developed AlPO4- based materials with increased basic properties and hence high selectivities (99 mol%) to the base-catalysed cleavage of MBOH yielding acetone and acetylene.
- Bautista, Felipa M.,Campelo, Juan M.,Garcia, Angel,Leon, Raquel M.,Luna, Diego,Marinas, Jose M.,Romero, Antonio A.,Navio, Jose A.,Macias, Manuel
-
p. 827 - 835
(2007/10/03)
-
- Autocatalytic fragmentation of acetoacetate derivatives as acid amplifiers to proliferate acid molecules
-
A novel concept of acid proliferation to improve the photosensitivity of chemically amplified photoresist materials is described by presenting the autocatalytic fragmentation of acetoacetates having a (sulfonyloxy)methyl residue to liberate the corresponding sulfonic acid. 2-Methyl-2-((methane- or p-toluenesulfonyloxy)methyl)acetoacetates were designed to be subjected to the acid-catalyzed fragmentation through the corresponding acetoacetic acids which are readily decarboxylated and undergo the subsequent β-elimination to give a sulfonic acid which can act as the autocatalyst to lead to the increment of acid concentration in geometric progression. Among the acetoacetates tested, tert-butyl 2-methyl-2-((p-toluenesulfonyloxy)methyl)acetoacetate was the most suitable reagent for the present purpose because of its reasonable thermal stability. A nonlinear generation of the sulfonic acid was confirmed in the acidolytic transformation of the acetoacetate in nonpolar solvents and in a film of poly[4-((tert-butoxycarbonyl)oxy)styrene] (PBOCSt), respectively. It was found that the addition of the acetoacetate to a film of PBOCSt doped with a photoacid generator enhances the photosensitivity characteristics.
- Arimitsu, Koji,Kudo, Kazuaki,Ichimura, Kunihiro
-
-
- Porphyrins with exocyclic rings. Part 12. Synthesis of meso,β-butano- and meso,β-pentanoporphyrins from cycloalka[b]pyrroles
-
Pyrroles 5 with b-face fused seven- or eight-membered carbocyclic rings were prepared in good yields by Knorr-type condensations with cycloheptanone or cyclooctanone, respectively. Treatment with lead tetraacetate in dichloromethane afforded the labile ω-acetates 8 and subsequent acid catalyzed condensation with α-unsubstituted pyrrole-2-carboxylates yielded the related pyrrolylcycloalka[b]pyrroles 29 and 30. The α-unsubstituted pyrroles 14 and 23 were prepared by condensing α,β-unsubstituted ketones, or their β-acetoxycarbonyl precursors, with benzyl N-tosylglycinate in the presence of DBU, followed by dehydration with POCl3-pyridine and base catalyzed elimination of p-toluenesulfinic acid. Dipyrrole dibenzyl esters 29 and 30 were hydrogenolysed over 10% Pd-C to give the corresponding dicarboxylic acids. Acid catalyzed condensation with diformyldipyrrylmethane 33 under modified MacDonald '2 + 2' conditions afforded a series of four cycloalkanoporphyrins 4a-d with seven- or eight-membered exocyclic rings. Although the meso,β-butanoporphyrins 4a and 4b were isolated in good yields, poorer results were obtained for the related meso,β-pentanoporphyrin: 4c and 4d. It is proposed that the eight-membered carbocyclic ring distorts the geometry of the open-chain tetrapyrrolic intermediates and this deleterious influence results in the lower yields observed.
- Bastian, Jolie A.,Lash, Timothy D.
-
p. 6299 - 6310
(2007/10/03)
-
- An abnormal reaction of esters of 3-hydroxy-3-methylbutan-2-one. A rapid synthesis of bullatenone and geiparvarin
-
A new rapid and facile synthesis of two natural products with the structure of3(2H)furanone is described by a cyclisation catalysed by cesium fluoride.
- Villemin, Didier,Jaffres, Paul-Alain,Hachemi, Messaoud
-
p. 537 - 538
(2007/10/03)
-
- Dehydration-hydration of α-alkynols over zeolite catalyst. Selective synthesis of conjugated enynes and α,β-unsaturated ketones
-
α-Alkynols 1 are convened in high yield and selectivity into conjugated enynes 2 or α,β-unsaturated ketones 3 by treatment with acid zeolites. The exclusive production of compounds 2 or 3 depends on the nature of the starting material 1 and experimental conditions.
- Sartori, Giovanni,Pastorio, Andrea,Maggi, Raimondo,Bigi, Franca
-
p. 8287 - 8296
(2007/10/03)
-
- A Novel Concept of Acid Proliferation. Autocatalytic Fragmentation of an Acetoacetate Derivative as an Acid Amplifier
-
tert-Butyl 2-methyl-2-(p-toluenesulfonyloxymethyl)acetoacetate was designed to be subjected to the acid-catalyzed fragmentation to liberate p-toluenesulfonic acid which can act as the autocatalyst to lead to the increment of the acid concentration in geometric progression.
- Ichimura, Kunihiro,Arimitsu, Koji,Kudo, Kazuaki
-
p. 551 - 552
(2007/10/03)
-
- Photooxygenation of vinyl sulfides: Substituent effects on the [2+2] cycloaddition versus Schenck ene reaction modes
-
Electron-accepting substituents at the para position of aryl vinyl sulfides 1 promote the ene reaction with singlet oxygen in competition with the usual [2+2] cycloaddition, while electron-donating substituents afford exclusively dioxetane product, which through their thermally labile nature decompose by C-C cleavage to the corresponding carbonyl fragments.
- Adam, Waldemar,Sampath Kumar,Saha-Moeller, Chantu R.
-
p. 7853 - 7854
(2007/10/02)
-
- Preparation and Benzoylation of 3-Hydroxy-2,3,5,5-tetramethyl-1-pyrroline 1-Oxide (3-Hydroxy-2,3,5,5-tetramethyl-4,5-dihydro-3H-pyrrole 1-Oxide)
-
Treatment of 2,3,5,5-tetramethyl-3-hydroxy-1-pyrroline 1-oxide 6, prepared from butanone in six steps, with benzoyl chloride under Schotten-Baumann conditions leads to an unprecedented dimerisation to give a spiro, tricyclic N-benzoyloxypyrrolidine in good yield.
- Gibson, Neil J.,Forrester, Alexander R.,Brown, Charles
-
p. 507 - 510
(2007/10/02)
-
- Regioselectivity of the Singlet Oxygen Ene Reaction (Schenck Reaction) with Vinylsilanes
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The ene reaction of singlet oxygen and vinylsilanes 1 with various substitution patterns and double-bond geometry has been studied. β-Silyl allylic hydroperoxides 2 were the major products of the photooxygenation, accompanied by smaller amounts of α,β-unsaturated ketones 3.The latter derive from decomposition of the regioisomeric α-hydroperoxy silanes 4 by elimination of silanol.Regioselectivities up to 97:3 were observed for vinylsilanes with a methyl group geminal to the silyl group and with cyclic derivatives.Z-Configurated substrates showed lower regioselectivity and reactivity.Elongation of the carbon chain at the geminal position also increased the amount enone formed.These results are rationalized in terms of stereoelectronic effects imposed by the silyl group on the ring-opening of the perepoxide intermediate.
- Adam, Waldemar,Richter, Markus J.
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p. 3335 - 3340
(2007/10/02)
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- Highly Regio- and Diastereoselective One-Pot Synthesis of Silyl Epoxy Alcohols and Vinylsilanes by Direct Hydroxy-Epoxidation
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A direct synthesis of silyl epoxy alcohols from vinylsilanes is described.It consists of the regioselective ene reaction of the vinylsilanes with singlet oxygen, which proceeds with predominant hydrogen abstraction at the position geminal to the silyl group.The resulting silyl allylic hydroperoxides were treated, without isolation, subsequently with Ti(O-i-Pr)4 to afford the silyl epoxy alcohols in good yields and very high diastereomeric ratios, which ranged from 93:7 to greater than 97:3.Alternatively, the vinylsilanes were photooxygenated directly in the presence of the titanium catalyst and the silyl epoxy alcohols obtained in good yields.The method was applied to di- and trisubstituted acyclic vinylsilanes with a methyl group geminal to silicon and cyclic derivatives all give consistently good results.In this novel hydroxy-epoxidation, the regioselectivity of the singlet oxygen ene reaction as well as the diastereoselectivity of the oxygen transfer can be controlled by the steering effects of the silyl group.
- Adam, Waldemar,Richter, Markus J.
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p. 3341 - 3346
(2007/10/02)
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- Production of unsaturated compounds
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Unsaturated compounds, in particular alkenyl ketones and cyano analogues, useful for polymerization with a variety of monomers to form photodegradable polymers, are formed by dehydrating a preformed liquid alkanol of the formula: where X is an activating group for this dehydration reaction, preferably -CO- or -CN, in the presence of a solid dehydration catalyst, which may be acid resin, alumina or mixtures thereof. Apparatus for carrying out the method and novel products also are described.
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- Reactions of Ozone with Unsaturated Organic Compounds
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Rate constants for the gas-phase reactions of ozone with a series of alkenes have been determined using a conventional static system.Ozone loss was monitored in excess of the hydrocarbon and rate data measured at 1 atmosphere total pressure over the temperature range 240-324 K.The Arrhenius parameters obtained are discussed in terms of structure-reactivity relationships.Product studies have been carried out for the reaction of O3 with the conjugated dienes, 1,3-butadiene, 2-methyl-1,3-butadiene (isoprene) and 2,3-dimethyl-1,3-butadiene in air.The results provide information on the decomposition pathways for the primary ozonides and the relative importance of ozone addition to the two double-bonds in isoprene.Chemical Kinetics / Elementary Reactions / Radicals
- Treacy, Jack,Hag, Mohamed El,O'Farrell, Denis,Sidebottom, Howard
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p. 422 - 427
(2007/10/02)
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- Syntheses of All-trans Acyclic Isoprenoid Pheromone Components
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All-trans acyclic isoprenoid skeletons were made through a two-step iterative sequence.The method involves the Claisen rearrangement of allyl vinyl ethers formed from allylic alcohols and the dimethyl acetal of methyl isopropenyl ketone, followed by LiAlH4 reduction of the α,β-unsaturated ketone formed by rearrangement.The α,β-unsaturated ketone was also transformed to the 2-methyl-1-propenyl group by using a one-pot deoxygenation reaction for the synthesis of (E)-β-farnesene, (E)-β-springene and dendrolasin.
- Baeckstroem, Peter,Li, Lanna
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p. 6533 - 6538
(2007/10/02)
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- Hydrophobic Vitamin B12. V. Electrochemical Carbon-Skeleton Rearrangement as Catalyzed by Hydrophobic Vitamin B12: Reaction Mechanisms and Migratory Aptitude of Functional Groups
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The carbon-skeleton rearrangements as catalyzed by heptamethyl cobyrinate perchlorate, 1ester>ClO4, were investigated under electrochemical conditions.The controlled-potential electrolysis of 2,2-bis(ethoxycarbonyl)-1-bromopropane, which is considered to be a model substrate for methylmalonyl-CoA mutase, was catalyzed by 1ester>ClO4 in N,N-dimethylformamide to give the rearrangement product, 1,2-bis(ethoxycarbonyl)propane, as a major one at -1.5 V vs.SCE in the presence of acetic acid and at potentials more cathodic than -1.8 V vs.SCE without acetic acid in the dark.The electrochemical carbon-skeleton rearrangement was postulated to proceed via formation of anionic intermediates.The electrolyses of 1-bromo-2-cyano-2-ethoxycarbonylpropane, 2-acetyl-1-bromo-2-ethoxycarbonylpropane, and 1-bromo-2-propane with 1ester>ClO4 also afforded the corresponding carbon-skeleton rearrangement products.The results indicated that substrates with two electron-withdrawing groups placed on the β-carbon atom with combination of one carboxylic ester and one of carboxylic ester, acetyl, and cyano moieties readily gave the corresponding rearrangement products which were derived from individual migration of the substituent groups.Substrates with only one of the electron-withdrawing groups, carboxylic ester, acetyl, and cyano, did not give any rearrangement product, but a substrate with one thioester group afforded the corresponding rearrangement product.The migratory aptitude of electron-withdrawing groups was found to decrease in the order: COSR>COR>COOR>CN.Both electronic character and steric bulkiness of the migrating groups are apparently reflected on this tendency, even though relative contributions of these effects are much dependent on the nature of β-substituents.
- Murakami, Yukito,Hisaeda, Yoshio,Ozaki, Toshiaki,Tashiro, Takako,Ohno, Teruhisa,et al.
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p. 311 - 324
(2007/10/02)
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- A NEW SYNTHESIS OF α,β-UNSATURATED KETONES. ALLYLIC ALKYLATION OF 1-ISOCYANO-1-TOSYLALKENES
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Ketones (1) are homologated to enones 2 by alkylating (introduction of R3) the condensation products 4 (derived from 1 and tosylmethyl isocyanide), followed by acid catalyzed hydrolysis.
- Moskal, Janusz,Leusen, Albert M. van
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p. 2585 - 2588
(2007/10/02)
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- Rhodium-Catalyzed C,C-Double Bond Cleavage by Molecular Oxygen
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Acetylacetonatorhodiumolefin systems, allylrhodium complexes, or (Ph3P)3RhCl catalyzed the conversion of alkenes and molecular oxygen to carbonyl compounds via C=C-bond cleavage.For example, 2,3-dimethyl-2-butene was transformed into acetone.Butadiene and isoprene also undergo oxidative C=C-bond cleavage to form acrylaldehyde and related compounds.
- Boennemann, Helmut,Nunez, Washington,Rohe, Dieter M. M.
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p. 177 - 185
(2007/10/02)
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- Monoozonolysis of 2,3-Dimethylbutadiene in Pentane and in Methanol
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2,3-Dimethylbutadiene (1) was attacked predominantly at only one double bond by a deficient amount of ozone in pentane or in methanol.In pentane, an α,β-unsaturated ozonide (4) was formed, which was further converted into an α,β-dibromoozonide (2) and into an α,β-epoxyozonide (6), respectively.Ozonolysis of 1 in methanol afforded an α,β-unsaturated methoxy hydroperoxide (8) and formaldehyde as well as a joint coproduct (9) of the latter two fragments.
- Griesbaum, Karl,Keul, Helmut,Agarwal, Sudhir,Zwick, Gerhard
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p. 409 - 415
(2007/10/02)
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- Process for preparation of adjacently disubstituted ketones
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A novel 7-hydroxyprostaglandin E1, or a stereoisomer thereof, or a protected derivative thereof, having the following formula: STR1 wherein R8 represents H, CH3 or C2 H5, R9 represents H or CH3, R10 and R11 are identical or different, and each represents H, tetrahydropyranyl or t-butyldimethylsilyl. Also provided is a process for producing an adjacently disubstituted ketone including the above compounds, i.e. 7-oxoprostaglandin, etc. which comprises reacting an α,β-unsaturated carbonyl compound with a cuprous salt and an organolithium compound in an aprotic inert organic medium in the presence of trialkylphosphine, the amounts of said cuprous salt and said organolithium compound being substantially equimolar, and reacting the product with a protected acetal derivative of an organic carbonyl compound or an aldehyde in the presence of a Lewis acid, if necessary, followed by reacting the product with a proton donor.
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- Kinetics of the Unimolecular Elimination of Chlorobutanones in the Gas Phase
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The gas-phase unimolecular elimination of 3-chloro-3-methyl-2-butanone has been investigated, in a static system and seasoned vessel, over the temperature range of 340-395 deg C and the pressure range of 60-190 torr.The reaction is homogeneous and unimolecular, follows a first-order rate law, and is invariable in the presence of cyclohexane, a radical-chain inhibitor.The products are isopropenyl methyl ketone and hydrogen chloride.The rate coefficients are given by the Arrhenius equation log k1 (s-1) = (12.56+/-0.31)-(190.8+/-3.7) kJ mol-1 (2.303RT)-1.When primary, secondary, and tertiary chlorobutanones are compared the presence of acetyl at the Cβ-Cl bond causes a significant rate enhancement due to the -M effect.However, if this substituent is at the Cα-Cl bond , deactivation in rate of elimination of these compounds is observed.The present work could well provide a general view on the effect of the acetyl substituent at the Cα-Cl and Cβ-Cl bonds in the molecular elimination of haloketones in the gas phase.
- Chuhani, Gabriel,Hernandez A, Jose A.
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p. 4139 - 4141
(2007/10/02)
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- Oxydation anodique de β-cetocarboxylates en milieu aqueux ou hydroorganique. Application a la synthese de γ-dicetones, de cetones ethyleniques et de cetoamides
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A systematic study of the anodic oxidation of β-ketocarboxylate anions in aqueous or hydroorganic solvents allows to distinguish the factors directing this reaction.Thus, it is possible by the appropriate choice of reaction medium and structure of the starting ion to synthesize products such as γ diketones, ethylenic ketones and ketoamides.
- Chkir, Moncef,Lelandais, Daniel,Bacquet, Cathy
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p. 945 - 951
(2007/10/02)
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- Reactions of methylaluminium compounds with methacrylonitrile
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Reactions of trimethylaluminium, dimethylaluminium chloride and methylaluminium dichloride with methacrylonitrile have been investigated. These reactions afford corresponding donor-acceptor complexes. At elevated temperatures they react to yield methyl is
- Kuran,Pasynkiewicz,Muszynski
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