Showing papers on "Methyl vinyl ketone published in 1999"

The first example of Michael addition catalysed by modified Mg–Al hydrotalcite

Abstract: Selective 1,4-additions (Michael reactions) on methyl vinyl ketone, methyl acrylate, simple and substituted chalcones by donors such as nitroalkane, malononitrile, diethylmalonate, cyanoacetamide and thiols were catalysed by solid base, modified Mg-Al hydrotalcite as catalyst in quantitative yields in liquid phase under mild reaction conditions. Products of undesirable side reactions resulting from 1,2-addition, polymerisation and bis-addition are not observed. The work-up procedure is simplified by simple filtration with the use of solid bases.

Measurement of Hydroxy Carbonyls and Other Carbonyls in Ambient Air Using Pentafluorobenzyl Alcohol as a Chemical Ionization Reagent

Abstract: Hydroxy carbonyls and other carbonyls were measured in air by sampling with impingers filled with an aqueous solution of O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine hydrochloride (PFBHA), further reacting the PFBHA derivatives of hydroxy carbonyls with bis(trimethylsilyl)trifluoroacetamide (BSTFA), and detecting the derivatives with gas chromatography/ion trap mass spectrometry. Molecular weight determinations of ultratrace (pptv) levels of the derivatives in the presence of coeluting interferences was made possible by using pentafluorobenzyl alcohol (PFBOH) as a chemical ionization reagent. Methyl vinyl ketone, methacrolein, methylglyoxal, glycolaldehyde, and hydroxyacetone were identified in air collected in Azusa, CA. Methyl vinyl ketone, methacrolein, methylglyoxal, hydroxyacetone, glyoxal, and 3-hydroxy-2-butanone were identified in samples collected in Davis, CA. To our knowledge, this is the first report of hydroxyacetone and 3-hydroxy-2-butanone in the ambient atmosphere. This work is a significa...

Atmospheric photochemical degradation of 1,4-unsaturated dicarbonyls

Abstract: To better understand fates of aromatics hydrocarbon species in the atmosphere, the authors have investigated the transformation chemistry of butenedial (CHOCH{double{underscore}bond}CHCHO), 4-oxo-2-pentenal (CH{sub 3}COCH{double{underscore}bond}CHCHO), and 3-hexene-2, 5-dione (CH{sub 3}COCH{double{underscore}bond}CHCOCH{sub 3}) These 1,4-unsaturated dicarbonyls are known to be products of aromatic photochemical oxidation Both hydroxyl radical (OH) and ozone (O{sub 3}) initiated smog chamber experiments under atmospheric conditions were conducted in the University of North Carolina outdoor smog chamber Carbonyl intermediates and products were measured using the O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine derivatization method followed by gas chromatography/ion trap mass spectrometry analysis Carbonyl products detected and identified by comparison with standards in the OH-initiated photooxidation of butenedial include formaldehyde, acrolein, glycolaldehyde, glyoxal, and malonaldehyde (CHOCH{sub 2}CHO) For 4-oxo-2-pentenal, the carbonyl products were formaldehyde, methyl vinyl ketone, glycolaldehyde, hydroxyacetone, glyoxal, methylglyoxal, and malonaldehyde for 3-hexene-2,5-dione the products were formaldehyde, acetaldehyde, acetone, hydroxyacetone, and methylglyoxal Carbonyl products detected in the P{sub 3}-initiated experiments with cyclohexane as the OH scavenger were formaldehyde and glyoxal in butenedial; formaldehyde, glyoxal, methyl-glyoxal, and malonaldehyde in 4-oxo-2-pentenal; and formaldehyde and methylglyoxal in 3-hexene-2,5-dione

A kinetic study of the reactions of NO3 with methyl vinyl ketone, methacrolein, acrolein, methyl acrylate and methyl methacrylate

Abstract: Absolute and relative-rate techniques have been used to obtain rate coefficients for the reactions: NO3+CH3C(O)CHCH2→products (1), NO3+CH2C(CH3)CHO→products (2), NO3+CH2CHCHO→ products (3), and NO3+CH2CHC(O)OCH3→products (4). The reaction NO3+CH2C(CH3)C(O)OCH3→ products (5), has been investigated by a relative-rate method only. The rate coefficients obtained by the relative-rate method at T=296±2 K and P=760 Torr are k1=(4.7±1.7)×10-16 cm3 molecule-1 s-1, k2=(3.7±1.0)×10-15 cm3 molecule-1 s-1, k3=(1.1±0.4)×10-15 cm3 molecule-1 s-1, k4=(1.0±0.6)×10-16 cm3 molecule-1 s-1 and k5=(3.6±1.3)×10-15 cm3 molecule-1 s-1. The rate coefficients determined by the discharge-flow technique at low pressure (P=1–10 Torr) and at T=293–303 K are k1=(3.2±0.6)×10-16 cm3 molecule-1 s-1, k2=(9.6±2.0)×10-15 cm3 molecule-1 s-1, k3=(8.9±2.8)×10-15 cm3 molecule-1 s-1, k4=(1.9±0.4)×10-16 cm3 molecule-1 s-1. The discrepancy between the values obtained from the relative-rate technique and the absolute technique are discussed and explained in terms of interference in the absolute study caused by secondary chemistry and fast-reacting impurities. Product studies reveal that methyl glyoxal is a product of reactions (1) and (2) along with peroxymethacryloyl nitrate (MPAN) for reaction (2) in air. A diurnally varying boundary-layer model suggests that reaction (2) is an important loss process for methacrolein and that it can lead to the generation of OH at night.

The aza-ene reaction of heterocyclic ketene aminals with enones: an efficient and simple synthetic route to fused di- and tri-heterocycles

Abstract: Heterocyclic ketene aminals bearing a secondary amino moiety acted as hetero-ene components to react with a number of enones under very mild conditions. The reaction of five- and six-membered heterocyclic ketene aminals 5 and 8 with methyl vinyl ketone proceeded effectively through the aza-ene addition, imine–enamine tautomerization and intramolecular cyclization to give good yields of 8-aroyl-5-hydroxy-5-methyl-1,2,3,5,6,7-hexahydroimidazo[1,2-a]pyridines 6 and 9-aroyl-6-hydroxy-6-methyl-1,2,3,4,7,8-hexahydroxy-6H-pyrido[1,2-a]pyrimidines 9, respectively. When methyl vinyl ketone was present in excess, preliminarily formed product 6 underwent a second aza-ene reaction followed by intramolecular cyclization and water-participating debenzoylation, to yield the cisoid-4,9-dihydroxy-4,9-dimethyl-1,2,5,6,6a,7,8,10α-octahydro-4H,9H-imidazo[1,2,3-ij][1,8]naphthyridin-10α-ylium benzoate 7 as the sole product. In refluxing acetonitrile, heterocyclic ketene aminals 5 underwent aza-ene addition and cyclocondensation reaction with a number of substituted α,β-unsaturated ketones to afford 1,2,3,7-tetrahydroimidazo[1,2-a]pyridine derivatives 23 while tricyclic imidazo[1,2-a]quinoline derivatives were easily obtained when 2-benzylidene-cyclohexanone and -cyclohexane-1,3-dione were used as enophiles. The effect of the structures of heterocyclic ketene aminals, particularly of the intramolecular hydrogen bond, on the aza-ene reactivity is also discussed.

Laboratory Kinetic Studies of the Reactions of Cl Atoms with Species of Biogenic Origin: δ3-Carene, Isoprene, Methacrolein and Methyl Vinyl Ketone

Abstract: The rate coefficients for the reaction between atomic chlorine and a number of naturally occurring species have been measured at ambient temperature and atmospheric pressure using the relative rate technique. The values obtained were (4.0 ± 0.8) × 10-10, (2.1 ± 0.5) × 10-10, (3.2 ± 0.5) × 10-10, and (4.9 ± 0.5) × 10-10 cm3 molecule-1 s-1, for reactions with isoprene, methyl vinyl ketone, methacrolein and δ3-carene, respectively. The value obtained for isoprene compares favourably with previously reported values. No values have been reported to date for the rate constants of the other reactions.

Effect of high pressure on Michael and Henry reactions between ketones and nitroalkanes

Abstract: The kinetic pressure effect on some specific Michael and Henry reactions is investigated. The observed activation volumes of the Michael reaction between nitromethane and methyl vinyl ketone are largely dependent on the magnitude of the electrostriction effect, which is highest in the lanthanide-catalyzed reaction, still important in the aqueous reaction and lowest in the base-catalyzed version. In the latter case, the reverse reaction is insensitive to pressure. These results apply also to the Henry addition of nitroalkanes to ketones. The positive pressure effect can be used for the chemoselective synthesis of nitroalcohols from ketones.

Enzyme catalysed modification of synthetic polymers

Abstract: The first example of an enzyme catalysed modification of the backbone of a synthetic polymer is described. An immobilised lipase from Candida antarctica (Novozym 435) catalyses the selective epoxidation of polybutadiene in organic solvents in the presence of hydrogen peroxide and catalytic quantities of acetic acid. The cis and trans alkene bonds of the backbone are epoxidised in yields of up to 60% whilst the pendent vinyl groups are untouched. The effect of varying a number of reaction parameters suggests that higher yields of epoxide could not be obtained because of the conformational properties of the partially epoxidised polymer. Application of this same enzymatic process to the Baeyer–Villiger reactions of poly(phenyl vinyl ketone) and poly(methyl vinyl ketone) were unsuccessful. The lack of reactivity was found to be a property of the polymers rather than of the enzymatic system.

Electroassisted catalysis of the reductive coupling of 2-bromooctane and methyl vinyl ketone by a binuclear cobalt–salen–iron complex in DMF solution: electrosynthesis and cyclic voltammetry analysis

Abstract: We report in this study the combined use of a CoSalen [H2Salen=bis(salicylidene)ethane-1,2-diamine] complex and an undivided electrochemical cell process in the electroassisted reductive coupling of 2-bromooctane and methyl vinyl ketone with satisfactory results. Correlation between the electroanalytical analysis of the reactivity of CoSalen in the presence of 2-bromooctane and methyl vinyl ketone and the electrosynthesis performed in an undivided electrochemical cell with a sacrificial iron anode allows us to suggest that a heterobinuclear Co–Salen–Fe complex is the effective catalyst of the considered reaction. Stability of this intermediate during preparative electrolysis is also discussed.

Dipeptides from methionine and S-methylcysteine as chiral ligands for asymmetric Michael reactions

Abstract: Dipeptides derived from methionine and S-methylcysteine 3a–d have been prepared and screened as chiral ligands in combination with 13 metal salts 4a–m towards the catalysis of an asymmetric Michael reaction of a β-keto ester 1 with methyl vinyl ketone 2 resulting in an optimal ee of 18% achieved with FeCl3· 6 H2O 4c as the metal salt.

Reactive Flux Calculations of Methyl Vinyl Ketone Reacting with Cyclopentadiene in Water

Abstract: Molecular dynamics and reactive flux simulations of the Diels−Alder reaction of methyl vinyl ketone (MVK) reacting with cyclopentadiene (CPD) in water have been carried out to calculate the activation free energy and transmission coefficient for the reaction. For this purpose, an empirical potential energy surface (PES) of the reaction was developed by first constructing an intramolecular PES of MVK + CPD using the B3LYP/6-31+g* level of ab initio theory. This calculation predicts that the reaction barrier height of MVK + CPD in the gas phase is 16 kcal/mol. The MVK + CPD complex was then surrounded by 215 SPC/F2 water molecules, and the activation free energy is seen to be reduced by 2.2 kcal/mol compared to that of the gas phase. The initial conditions for the reactive flux calculations were obtained at T = 300 K by a Nose-Hoover chain dynamics algorithm that was recently developed for this purpose. These calculations show that the transmission coefficient for the reaction in water is 0.67 and therefore...

1,3-Dipolar Cycloaddition Reactions of the Ylide Derived from 6-Phenacyl-benzo[f][1,7]naphthyridinium Bromide

Abstract: The 1,3-dipolar cycloaddition reactions of 4,6-diazaphenanthrene 6-phenacylide formed in situ from the quaternary 6-phenacylbenzo[f][1,7]naphthyridinium bromide in basic medium were examined; methacrylic acid, methyl methacrylate, butyl vinyl ether, methyl vinyl ketone, maleic anhydride and dimethyl acetylenedicarboxylate were used as the dipolarophiles.

Synthesis of 11-Deoxydaunomycinone and Novel 10-Fluoroanthracyclinone Derivatives

Abstract: 11-Deoxydaunomycinone 15 and 10-fluoroanthracyclinone derivatives 9, 10 were obtained. Naphthalenone 4 prepared from 2-(2,4-pentadienyl)-1,3-dioxane 2 with methyl vinyl ketone and hydrolysis with HClO4 was condensed with phthalidesulfone 5 through Michael type reaction, and was converted to 7 by epoxidation. Epoxide 7 was transformed to trione 12 using reduction-oxidation or hydrofluorination process, and then to 15 by introducing several functional groups. Compound 8 obtained in the course of the reaction of epoxide 7 and HF/ Pyr was used for the synthesis of compounds 9, 10.

Template polymerization of acrylamide in the presence of several homo- and copolymers including methyl vinyl ketone, methyl methacrylate, and styrene

Abstract: Template polymerization of acrylamide (AAm) in the presence of several homo- and copolymers such as poly(methyl vinyl ketone) (poly-MVK), poly(methyl methacrylate) (poly-MMA), copoly(MVK-styrene) and copoly(MMA-styrene) was carried out in THF at 30 or 40°C. The rate of polymerization (Rp) of AAm was greatly enhanced by the presence of a template polymer. However, a small amount of styrene (St) units in the template polymer markedly decreased the Rp of AAm. It was assumed that the contamination of the St units in the chain of the template polymer impeded the continuous absorption of AAm monomers onto the active sites of the template polymer. Also, the effect of stereo-regularity of poly-MMA on the Rp and the number-average molecular weight (Mn) of the resulting poly-AAm was investigated. The syndiotactic poly-MMA had pronounced influence on the Rp of AAm and Mn of poly-AAm comparing with the isotactic poly-MMA. This effect can be explained in the terms of the different conformational features of the two ta...

New Polymer‐Supported Catalysts Derived from Cinchona Alkaloids: Their Use in the Asymmetric Michael Reaction.

Abstract: New polymer-supported catalysts derived from quinine and quinidine were elaborated and tested in the conjugate addition between enamino ester 13 and methyl vinyl ketone. By employing a 7-atom-length spacer, an excellent enantioselectivity was observed (87%).

Study on the novel rearrangement reaction of bicyclic acetal compound by using accl-nai

Abstract: for ether cleavage were also proposed as shown inScheme 1. The 5-membered acetoxonium intermediate 5,which was formed through selective C5-O6 bond cleavage,was the key and common intermediate for the products 2a,3a and 4a. The enone 2a was formed via regioselectivenucleophilic attack of iodide ion (secondary vs tertiary car-bon) followed by deiodo-olefination. The acetate anion wasalso produced during this process and used as a nucleophileon the intermediate 5 to make diacetate 4a. The mono-acetated ethylene 3a was formed from the elimination reac-tion of the intermediate 5 by the iodide or acetate ion as abase.For clear explanation for these transformation mechanisms,we introduced deuterated methyl at C7 as a 2 : 1 ratio of exo-acetal 1b and endo-acetal 1c from the methyl vinyl ketone(MVK) dimer 7 (Scheme 2). The exo-preference by usingGrignard reagent in this system has been known.

Clay‐Catalyzed Solventless Addition Reactions of Furan with α,β‐Unsaturated Carbonyl Compounds.

Abstract: The reaction of furan with α,β-unsaturated carbonyl dienophiles catalyzed by K10 montmorillonite in the absence of organic solvents produces the corresponding Diels-Alder adducts and, in the case of methyl vinyl ketone, Michael-type products, under much milder conditions than the conventional protocols. The results are consistent with acid catalysis on the clay surface. Acrylates gave lower yields and/or decomposition products. The reaction can be extended to alkynic substrates such as DMAD to afford cycloadducts in good yields.

Synthesis of 11-Deoxydaunomycinone and Novel 10-Fluoroanthracyclinone Derivatives.

Abstract: 11-Deoxydaunomycinone 15 and 10-fluoroanthracyclinone derivatives 9, 10 were obtained. Naphthalenone 4 prepared from 2-(2,4-pentadienyl)-1,3-dioxane 2 with methyl vinyl ketone and hydrolysis with HClO4 was condensed with phthalidesulfone 5 through Michael type reaction, and was converted to 7 by epoxidation. Epoxide 7 was transformed to trione 12 using reduction-oxidation or hydrofluorination process, and then to 15 by introducing several functional groups. Compound 8 obtained in the course of the reaction of epoxide 7 and HF/ Pyr was used for the synthesis of compounds 9, 10.

Novel Diamino and Diimino Thioethers — Chiral Tridentate Ligands for Asymmetric Michael Reactions?

Abstract: Novel C2-symmetric enantiopure β,β′-diamino thioethers 1 and β,β′-diimino thioethers 2 have been prepared from chiral α-amino acids. Nine of these compounds have been screened as ligands, in combination with 13 metal salts, with a view to achieving the enantioselective catalysis of a Michael reaction of a β-oxo ester with methyl vinyl ketone resulting in an optimal ee of 17%.