- First preparation of 5-allyl-1,3-oxazolidine-2-thione (napoleiferin), a natural homolog of 5-vinyl-1,3-oxazolidine-2-thione (goitrin)
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The preparation of 5-allyl-1,3-oxazolidine-2-thione (napoleiferin) 5 via a practical synthesis of but-3-enal 2 and the key intermediate 1-aminopent- 4-en-2-ol 4 is described for the first time.
- Latxague,Gardrat
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p. 1627 - 1637
(2007/10/03)
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- Vinyl ether hydrolysis. XXIX. 1-Methoxy-1,3-butadiene: reaction mechanism and implication for hydrolysis of the mutagen fecapentaene-12
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The hydrolysis of cis- and trans-1-methoxy-1,3-butadiene in aqueous solution occurs by hydron transfer to the δ-carbon atom with little or no β-hydronation to give crotonaldehyde as essentially the sole aldehyde product. The reaction gives appreciable hydronium-ion isotope effects in the normal direction (cis:kH+/kD+ = 2.60, trans: kH+/kD+ = 3.52) and shows general acid catalysis; five carboxylic acid catalytic coefficients for hydrolysis of the trans isomer give a good Broensted relation with the exponent α = 0.59. This is taken as evidence that these reactions occur by the conventional mechanism for vinyl ether hydrolysis involving rate-determining hydron transfer to substrate carbon followed by rapid formation and decomposition of a hemiacetal intermediate. Comparison of the reactivity of the present dienyl ethers with that of their monoenyl analog, methyl vinyl ether, shows that introduction of the second double bond decreases reactivity considerably: the hydronium-ion catalytic coefficient is reduced by a factor of 8.3 for the trans isomer and by a factor of 160 for the cis isomer. This reduction supports a hypothesis advanced to explain the occurrence of reaction by a different mechanism recently discovered in the hydrolysis of the strongly mutagenic polyenyl ether, fecapentaene-12.
- Chiang, Yvonne,Eliason, Robert,Guo, Gary H.-X.,Kresge, A. Jerry
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p. 1632 - 1636
(2007/10/02)
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- Visible Light Induced Reactions of NO2 with Conjugated Dienes in a Low-Temperature Ar Matrix
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Visible light induced oxygen atom transfer from NO2 to conjugated dienes has been investigated in a low-temperature Ar matrix, where the dienes are 1,3-butadiene (BD), 2-methyl-1,3-butadiene (isoprene), and 2,3-dimethyl-1,3-butadiene (DMB).In each diene/NO2/Ar system, the corresponding nitrite radical, oxirane, aldehyde, and NO were obtained as the photochemical reaction products.The reactions are initiated by the formation of undetecteable short-lived oxirane biradical and NO due to visible light induced O atom transfer from NO2 to the conjugated dienes. (1) The recombination of oxirane biradicals and neighboring NO gives the nitrite radicals as the photochemical intermediate. (2) The ring closure of the biradicals leads to the formation of oxiranes. (3) The intramolecular H atom transfer of biradicals leads to the formation of aldehydes.The visible photolysis of the nitrite radicals gives rise to oxirane, aldehyde, and NO.The reaction rates are derived by measuring the absorbance changes of the products upon the 582-nm irradiation.The methyl substituent effect on the reactivity is discussed.
- Tanaka, Nobuaki,Kajii, Yoshizumi,Shibuya, Kazuhiko,Nakata, Munetaka
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p. 7048 - 7053
(2007/10/02)
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- Photolysis of Alkyl 4-Nitrobenzenesulfenates. A New and Versatile Method for the Generation of Free Radicals
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The irradiation of alkyl 4-nitrobenzenesulfenates with >300-nm wavelength light in benzene solution results in the homolytic cleavage of the O-S bond.The tertiary alkoxy radicals thus formed undergo β scission to produce carbon-centered free radicals in e
- Pasto, Daniel J.,L'Hermine, Gael
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p. 5815 - 5816
(2007/10/02)
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- Simple Enols. 5. (Z)- and (E)-1-Hydroxy-1,3-butadiene
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(Z)- and (E)-1-hydroxybutadiene have been generated from their trimethylsilyl derivatives in slightly acidic aqueous acetonitrile and CH3OH-DMSO mixtures and characterized by NMR spectroscopy.The kinetics and products of ketonization of both dienols have been investigated.In aqueous solution they yield mixtures of (E)-2-butenal and 3-butenal whose proportions depend on pH.Analysis of the variation of product composition with pH indicates that (E)-1-hydroxybutadiene yields 90.1, 28.0, and 44.7percent of (E)-2-butenal in the H3O+, H2O, and HO--catalyzed reactions, whereas (Z)-1-hydroxybutadiene yields 69.8, 17.2, and 19.6percent.It is suggested that transmission of positive charge to the oxygen in the transition state for protonation at the 4-position is more efficient with the E than with the Z isomer, possibly because it is easier for the former to attain a planar conformation.No evidence was found for a mechanism that involves a cyclic transition state for the spontaneous ketonization of (Z)-butadienol.
- Capon, Brian,Guo, Bozhang
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p. 5144 - 5147
(2007/10/02)
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- PALLADIUM CATALYZED REACTION OF BUTADIENE MONOXIDE WITH CARBON DIOXIDE
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Carbon dioxide readily reacts with 1,3-butadiene monoxide in the presence of a catalytic amount of tetrakis(triphenylphosphine)palladium under ordinary pressure at 0 deg C to afford vinylethylene carbonate in a quantitative yield.
- Fujinami, Tatsuo,Suzuki, Takehiro,Kamiya, Masakuni,Fukuzawa, Shin-ichi,Sakai, Shizuyoshi
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p. 199 - 200
(2007/10/02)
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