- Reaction of acrolein with acetylperoxyl radicals in the gas-phase
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A rate constant for the epoxidation of acrolein by acetylperoxyl radicals has been determined to be k4 = (1.3±0.9)×104 dm3mol-1s-1 at 383 K, which is anomalously fast in comparison with the epoxidation of alkenes. Abstraction of the acyl hydrogen atom from acrolein by acetylperoxyl radicals at 393 K was found to be at least 60 times slower than from acetaldehyde and at least three orders of magnitude slower than abstraction of the acyl hydrogen atom of the epoxide of acrolein. The fast rate for epoxidation of acrolein and the slow rate for hydrogen abstraction provide an explanation for the anomalously slow rate for the autoxidation of acrolein and suggests that acrolein formed during the autoxidation of alkene will react further to give its epoxide, and not exclusively by abstraction of the acyl hydrogen atom as was previously accepted.
- Roden, Peter J.,Stark, Moray S.,Waddington, David J.
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- Prebiotic synthesis of aminooxazoline-5′-phosphates in water by oxidative phosphorylation
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RNA is essential to all life on Earth and is the leading candidate for the first biopolymer of life. Aminooxazolines have recently emerged as key prebiotic ribonucleotide precursors, and here we develop a novel strategy for aminooxazoline-5′-phosphate synthesis in water from prebiotic feedstocks. Oxidation of acrolein delivers glycidaldehyde (90%), which directs a regioselective phosphorylation in water and specifically affords 5′-phosphorylated nucleotide precursors in upto 36% yield. We also demonstrated a generational link between proteinogenic amino acids (Met, Glu, Gln) and nucleotide synthesis.
- Fernández-García,Grefenstette,Powner
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supporting information
p. 4919 - 4921
(2017/07/11)
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- Efficient epoxidation of electron-deficient alkenes with hydrogen peroxide catalyzed by [γ-PW10O38V2(μ-OH) 2]3-
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A divanadium-substituted phosphotungstate, [γ-PW10O 38V2(μ-OH)2]3- (I), showed the highest catalytic activity for the H2O2-based epoxidation of allyl acetate among vanadium and tungsten complexes with a turnover number of 210. In the presence of I, various kinds of electron-deficient alkenes with acetate, ether, carbonyl, and chloro groups at the allylic positions could chemoselectively be oxidized to the corresponding epoxides in high yields with only an equimolar amount of H2O2 with respect to the substrates. Even acrylonitrile and methacrylonitrile could be epoxidized without formation of the corresponding amides. In addition, I could rapidly (min) catalyze epoxidation of various kinds of terminal, internal, and cyclic alkenes with H;bsubesubbsubesub& under the stoichiometric conditions. The mechanistic, spectroscopic, and kinetic studies showed that the I-catalyzed epoxidation consists of the following three steps: 1) The reaction of I with H;bsubesubbsubesub& leads to reversible formation of a hydroperoxo species [I;circbsubesubbsubesubbsubesubcirccircbsupesup& (II), 2) the successive dehydration of II forms an active oxygen species with a peroxo group [ 2:2-O2)]3- (III), and 3) III reacts with alkene to form the corresponding epoxide. The kinetic studies showed that the present epoxidation proceeds via III. Catalytic activities of divanadium-substituted polyoxotungstates for epoxidation with H 2O2 were dependent on the different kinds of the heteroatoms (i.e., Si or P) in the catalyst and I was more active than [γ-SiW10O38V2(μ-OH)2] 4-. On the basis of the kinetic, spectroscopic, and computational results, including those of [γ-SiW10O38V 2(μ-OH)2]4-, the acidity of the hydroperoxo species in II would play an important role in the dehydration reactivity (i.e., k3). The largest k3 value of I leads to a significant increase in the catalytic activity of I under the more concentrated conditions. Copyright
- Kamata, Keigo,Sugahara, Kosei,Yonehara, Kazuhiro,Ishimoto, Ryo,Mizuno, Noritaka
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scheme or table
p. 7549 - 7559
(2011/08/03)
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- Intermediate thiazoles and process for the preparation of 2-chloro-5-chloromethyl-thiazole
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The present invention relates to intermediate thiazole compounds and a process for preparing 2-chloro-5-chloromethylthiazole which is a known compound useful for the preparation of insecticides.
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- Julia-Colonna stereoselective epoxidation of some α,β-unsaturated enones possessing a stereogenic centre at the γ-position: Synthesis of a protected galactonic acid derivative
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The oxidation of enones 6-8 using peroxide or percarbonate and polyleucines as catalysts gave the corresponding diastereomers 9-12 in high yield. The compound 9 was converted into the galactonic acid derivative 16 in five steps and in an overall yield of nearly 60%. Polyleucines are shown to be catalysts powerful enough to overturn the intrinsic stereocontrol in the chosen substrates.
- Ray, Peter C.,Roberts, Stanley M.
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p. 149 - 153
(2007/10/03)
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- Characterization of the enantioselective properties of the quinohemoprotein alcohol dehydrogenase of Acetobacter pasteurianus LMG 1635. 1. Different enantiomeric ratios of whole cells and purified enzyme in the kinetic resolution of racemic glycidol
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Resting cells of Acetobacter pasteurianus LMG 1635 (ATCC 12874) show appreciable enantioselectivity (E=16-18) in the oxidative kinetic resolution of racemic 2,3-epoxy-1-propanol, glycidol. Distinctly lower values (E=7-9) are observed for the ferricyanide-coupled oxidation of glycidol by the isolated quinohemoprotein alcohol dehydrogenase, QH-ADH, which is responsible for the enantiospecific oxidation step in whole cells. The accuracy of E-values from conversion experiments could be verified using complementary methods for the measurement of enantiomeric ratios. Effects of pH, detergent, the use of artificial electron acceptors, and the presence of intermediate aldehydes, could be accounted for. Measurements of E-values at successive stages of the purification showed that the drop in enantioselectivity correlates with the separation of QH-ADH from the cytoplasmic membrane. It is argued that the native arrangement of QH-ADH in the membrane-associated complex favors the higher E-values. The consequences of these findings for the use of whole cells versus purified enzymes in biocatalytic kinetic resolutions of chiral alcohols are discussed.
- Machado, Sonia Salgueiro,Wandel, Ute,Jongejan, Jaap A.,Straathof, Adrie J. J.,Duine, Johannis A.
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- Atmospheric degradation of glycidaldehyde: Photolysis and reaction with OH radicals
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Epoxide aldehydes have recently been detected among the oxidation products of aromatic hydrocarbons. Many epoxides are toxic and very little is known about their atmospheric fate. The products and kinetics of the atmospheric oxidation, OH radical reaction, and photolysis of glycidaldehyde have been investigated in a large volume reactor at 298 K using in situ long- path FT-IR spectroscopy for the analysis. A rate coefficient of k = (1.69 ± 0.04) x 10-11 cm3 molecule-1 s-1 has been determined for the reaction of glycidaldehyde with the OH radical using the relative kinetic technique. The UV absorption spectrum of glycidaldehyde was measured in the range 220380 nm from which upper limits of its photolysis frequencies in the troposphere have been deduced, e.g., J (hv) ~ 1.0 x 10-4 s-1 (for July 1, noon, and 50°N). The OH radical initiated photooxidation of glycidaldehyde yields CO, CO2, formic acid, formic acid anhydride, formaldehyde, and hydroperoxymethyl formate as major products. A reaction mechanism is postulated to account for the product formation. Epoxide aldehydes have recently been detected among the oxidation products of aromatic hydrocarbons. Many epoxides are toxic and very little is known about their atmospheric fate. The products and kinetics of the atmospheric oxidation, OH radical reaction, and photolysis of glycidaldehyde have been investigated in a large volume reactor at 298 K using in situ long-path FT-IR spectroscopy for the analysis. A rate coefficient of k = (1.69 ± 0.04) × 10-11 cm3 molecule-1 s-1 has been determined for the reaction of glycidaldehyde with the OH radical using the relative kinetic technique. The UV absorption spectrum of glycidaldehyde was measured in the range 220-380 nm from which upper limits of its photolysis frequencies in the troposphere have been deduced, e.g., J(hv) approx. 1.0 × 10-4 s-1 (for July 1, noon, and 50° N). The OH radical initiated photooxidation of glycidaldehyde yields CO, CO2, formic acid, formic acid anhydride, formaldehyde, and hydroperoxymethyl formate as major products. A reaction mechanism is postulated to account for the product formation.
- Ma,Barnes,Becker
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p. 3515 - 3521
(2007/10/03)
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- Mechanisms of formation of adducts from reactions of glycidaldehyde with 2′-deoxyguanosine and/or guanosine
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Convenient syntheses of rac-glycidaldehyde from rac-but-3-ene-1,2-diol and (R)-glycidaldehyde from D-mannitol are described. (R)-Glycidaldehyde (1) reacts with guanosine in water (pH 4-11, faster reaction at higher pH) to give initially 6(S)-hydroxy-7(S)-(hydroxymethyl)-3-(β-D-ribofuranosyl)-5,6,7- trihydroimidazo[1,2-a]purin-9(3H)-one (7a) and 6(S),7(R)-dihydroxy-3-(β-D-ribofuranosyl)-5,6,73-tetrahydropyrimido[1,2-a] purin-10(3H)-one (8a). The former decomposes to 7-(hydroxymethyl)-5,9-dihydro-9-oxo-3-(β-D-ribofuranosyl)imidazo[1,2-a] purine (3a), 5,9-dihydro-9-oxo-3-(β-D-ribofuranosyl)imidazo[1,2-a]purine (5a, 1,N2-ethenoguanosine), and formaldehyde, while the latter adduct is relatively stable. The position of the hydroxymethyl group on the imidazo ring of 7-(hydroxymethyl)-5,9-dihydro-9-oxo-3-(β-D-ribofuranosyl)imidazo-[1,2-a] purine was proved by 13C NMR analysis of adducts derived from [1-15N]guanosine and [amino-15N]guanosine. At longer reaction times, the adduct 7,7′-methylenebis[5,9-dihydro-9-oxo-3-(β-D-ribofuranosyl)imidazo[1,2- a]purine[ (4a) is formed from guanosine and glycidaldehyde. The structure analysis of this adduct was also aided by 13C NMR analysis of the 15N-labeled adduct derived from [1-15N]guanosine. Analogous adducts were obtained from the reaction between glycidaldehyde and deoxyguanosine. Mechanisms of formation of the adducts from glycidaldehyde and guanosine/deoxyguanosine are proposed and supported by model studies with simple amines. The formaldehyde produced in the reactions described reacts with guanosine to give the known adduct N2-(hydroxymethyl)guanosine (9).
- Golding, Bernard T.,Slaich, Pritpal K.,Kennedy, Gordon,Bleasdale, Christine,Watson, William P.
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p. 147 - 157
(2007/10/03)
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- Free-Radical Homolytic Substitution at Selenium: An Efficient Method for the Preparation of Selenophenes
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Substituted and unsubstituted 1-(benzylseleno)-4-iodobut-3-en-2-ols 12 and 2-(benzylseleno)-1-(2-iodophenyl)ethanols 18 react smoothly with tris(trimethylsilyl)silane in benzene at 80 deg C (AIBN initiator) to afford selenophenes 16 and benzoselenophenes 21 in excellent yield.These reactions presumably involve intramolecular homolytic substitution by aryl and vinyl radicals 14 and 20 at the selenium atom with the expulsion of benzyl radical followed by facile dehydration to afford the aromatic selenophene ring system in each case.Competitive rate studies on the ring closure of the 2-phenyl radical 25 in the presence of tri-n-butyltin hydride to give 2,3-dihydrobenzoselenophene (27) and 1-(benzylseleno)-2-phenylethane (28) provide a rate constant for ring closure (kc) of approximately 3E7 s- at 80 deg C.The determination of more accurate data is hampered by what we attribute to be the involvement of a slow, but competive nonradical process.
- Lyons, Jennifer E.,Schiesser, Carl H.,Sutej, Katarina
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p. 5632 - 5638
(2007/10/02)
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- Process for preparation of epoxy esters and intermediates prepared thereby
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This invention relates to a process for preparing epoxy esters, and intermediates prepared by this process, in particular, to a process which produces non-racemic epoxy esters which are of use as intermediates in the preparation of pharmaceutical compounds.
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- The Structures of Adducts from the Reaction between Guanosine and Glycidaldehyde (Oxiranecarbaldehyde): a 15N Labelling Study
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Reaction of guanosine (1a) with racemic glycidaldehyde (2) in aqueous medium at pH 10 gives 5,9-dihydro-9-oxo-3-β-D-ribofuranosylimidazopurine (1,N2-ethenoguanosine) (3c), its 7-hydroxymethyl derivative (3a), and methylene-7,7'-bis-5,9-dihydro-9-oxo-3-β-D-ribofuranosylimidazopurine (5); the structures of adducts (3a) and (5) were deduced from 13C n.m.r. analysis of 15N labelled adducts derived from guanosine (1b) and guanosine (1c).
- Golding, Bernard T.,Slaich, Pritpal K.,Watson, William P.
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p. 515 - 517
(2007/10/02)
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- Conformational Analysis of the Cyclopropylacyl, Oxiranylacyl, and Aziridinylacyl Radicals by Electron Spin Resonance Spectroscopy
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A series of ring-substituted cyclopropylacyl, oxiran-2-ylacyl, and aziridin-2-ylacyl radicals have been prepared principally by the reaction of photolytically generated t-butoxyl radicals with the corresponding aldehydes.The e.s.r. spectra show that the cyclopropylacyl ?-radicals exist in s-cis- and s-trans-conformations of approximately equal stability, in which the plane of the acyl group bisects the ring (as it does in the parent aldehyde), and simulation of the spectra through the region of intermediate rates of exchange show that the barrier to rotation is ca. 17.5 kJ*mol-1.The behaviour of the trans-2-ethoxycarbonylcyclopropylacyl and 2,2-dimethylcyclopropylacyl radicals is similar.The oxiranylacyl and trans-3-methyloxiranylacyl radicals exist in the same two conformations with a rather lower barrier, and the N-alkylaziridinylacyl radicals appear to have a lower barrier still.
- Davies, Alwyn G.,Sutcliffe, Roger
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p. 1483 - 1488
(2007/10/02)
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