- SYNTHESIS AND VALENCE BOND ISOMERIZATION OF CYCLOOCTATROPOLONE
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Cyclooctatropolone (4) was synthesized by hydrolysis of an adduct of 1H-cyclopentacyclooctene and dichloroketene.The tropolone was found to exist as a mixture of valence bond isomers (4a) and (4b).
- Oda, Mitsunori,Morita, Noboru,Asao, Toyonobu
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Read Online
- Halogenated Ketenes. 36. Reactions of Chloroketenes with Ketene Acetals
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The products of the reactions of ketenes and ketene acetals are dependent upon substitution in the ketene acetals.Dichloroketene reacts with dimethylketene dimethyl acetal to regiospecifically yield the cyclobutanone.The reaction of methylchloroketene and ketene diethyl acetal yields an acyclic product, an acylketene acetal.Chloro-, dichloro-, and methylchloroketenes react with O-silylated ketene acetals to yield acyclic unsaturated esters.Dichloroketene reacts with the acylketene acetal, (α-chloropropionyl)ketene diethyl acetal, to yield a (4 + 2) cycloaddition product, a δ-lactone.All of these results are consistent with a two-step process involving a dipolar intermediate.
- Brady, William T.,Watts, Ronald D.
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Read Online
- Efficient approach to 1,2-diazepines via formal diazomethylene insertion into the C-C bond of cyclobutenones
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Efficient monocyclic 1,2-diazepine formation via a tandem electrocyclization reaction of cyclobutenones with lithiodiazoacetate is demonstrated. The reaction proceeds through an oxy anion-accelerated 4π-ring opening of cyclobutene followed by an 8π-ring closure of the resultant oxy anion-substituted diazo-diene under mild conditions to furnish a 1,2-diazepine via formal diazomethylene insertion into the C-C bond of cyclobutenone.
- Sugimoto, Kenji,Hayashi, Rie,Nemoto, Hideo,Toyooka, Naoki,Matsuya, Yuji
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supporting information; experimental part
p. 3510 - 3513
(2012/07/31)
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- A new approach to the synthesis of the 17β-butenolide fragment of cardenolides
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A new, efficient synthesis of the 17β-butenolide fragment characteristic of cardenolides is effected by [2 + 2]-cycloaddition of dichloroketene to 3β-acetoxypregna-5,20-diene, as a key step.
- Paryzek, Zdzislaw,Blaszczyk, Krzysztof
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p. 5913 - 5914
(2007/10/03)
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- Flash Vacuum Thermolysis of Four Membered Ring Containing Nitrogen Atom. Part III. Thermal Decomposition of β-Lactams
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The thermal decomposition of β-lactams under FVT conditions was studied. It has been found that the regiochemistry of the ring cleavage depends on the nature of substituents. 1,4-Diradical stepwise mechanism of these reactions has been postulated. Key words: β-lactams, flash vacuum thermolysis
- Bartnik, R.,Lesniak, S.
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p. 2605 - 2612
(2007/10/02)
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- Cycloadditions of 2,4,6-Cycloheptatriene-1-imines with Chloroketenes: Facile and High-Yield One-Pot Synthesis of 1-Azaazulen-2(1H)-ones
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Simple heating of mixtures of N-arylcycloheptatriene-1-imines and acyl chlorides in the presence of an excess amount of triethylamine afforded 1-azaazulen-2(1H)-ones in high yields.The intermediacy of the cycloadducts between the 2,4,6-cycloheptatriene-1-imines and ketenes were confirmed by their isolations.Analogous results were obtained with tropone hydrazones.
- Ito, Kazuaki,Saito, Katsuhiro,Takahashi, Kensuke
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p. 812 - 816
(2007/10/02)
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- STERICALLY SCREENED HALOGENOCYCLOBUTANONES VIII. ADDITION OF DICHLOROKETENE TO METHYLENECYCLOPROPANES SUBSTITUTED AT THE DOUBLE BOND
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-Cycloaddition of dichloroketene to metylenecyclopropanes substituted at the double bond takes place regiospecifically with the formation of spirohexanones, containing a carbonyl group at position 4.Under electron impact the obtained compounds undergo dissociation mainly into substituted dichloroethylene and cyclopropylidenecarbonyl.This can be used as a test for determining the mutual arrangement of the carbonyl group in the spiro fragment in the adducts of dichloroketene and methylenecyclopropanes.
- Donskaya, N. A,,Bessmertnykh, A. G.,Lukovskii, B. A.,Kisina, M. Yu.,Ryabova, M. A.
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p. 2249 - 2253
(2007/10/02)
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- Kinetics of reactions of chlorinated vinyl radicals CH2CCl and C2Cl3 with molecular oxygen
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The kinetics of the reactions of CH2CCl and C2Cl3 radicals with O2 have been studied in a tubular flow reactor coupled to a photoionization mass spectrometer in the temperature range 298-648 K. Radicals were produced by the homogeneous photolysis of a suitable precursor using an excimer laser. The observed or indicated reaction mechanisms as well as the rate constants, which were measured as a function of density and temperature, suggest that both of these reactions proceed via the formation of a short-lived bound RO2 intermediate that can either decompose back to the original reactants or form new oxygen-containing products following internal rearrangement of the adduct.
- Russell,Seetula,Gutman,Senkan
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p. 1934 - 1938
(2007/10/02)
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- ASYMMETRIC INDUCTION IN THE CYCLOADDITION REACTION OF DICHLOROKETENE WITH CHIRAL ENOL ETHERS. A VERSATILE APPROACH TO OPTICALLY ACTIVE CYCLOPENTENONE DERIVATIVES.
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Significant asymmetric induction has been observed in the cycloaddition reaction of dichloroketene with chiral enol ethers.The resultant diastereomeric cyclobutanones have been converted to synthetically useful α-chlorocyclopentenones in optically active form.
- Greene, Andrew E.,Charbonnier, Florence
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p. 5525 - 5528
(2007/10/02)
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- HEI PHOTOELECTRON SPECTRA OF UNSTABLE MOLECULES: MONO- AND DIHALOGENOKETENES
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HeI Photoelectron spectra are reported for the mono- and di-chloro-and-bromo-ketenes (XHC=C=O and X2C=C=O, X=Cl,Br) generated in high yield as unstable molecules from thermolysis of acid halides.The spectra are discussed and assigned by reference to the parent ketene molecule, orbital trends, and comparison with theoretical calculations.
- Colbourne, David,Westwood, Nicholas P. C.
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p. 2049 - 2054
(2007/10/02)
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- SYNTHESIS OF 4-CARBOXY-2-THIABICYCLOHEPTAN-6-ONES VIA 3-CARBOXY-2,3-DIHYDROTHIOPHENES: POTENTIAL β-LACTAMASE INHIBITORS
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3-Carboalkoxy-2,3-dihydrothiophenes, available by Birch reduction of thiophene-3-carboxylic acid or more efficiently by deconjugation of 2,5-dihydrothiophene-3-carboxylic acid by reaction with ethyl chloroformate and triethylamine, undergo cycloaddition reactions with dichloroketene leading to 4-carboxy-7,7-dichloro-2-thiabicycloheptan-6-ones which are of interest as potential β-lactamase inhibitors.
- Lange, Gerald,Savard, Marc E.,Viswanatha, Thammaiah,Dmitrienko, Gary I.
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p. 1791 - 1794
(2007/10/02)
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- Additive Pummerer Rearrangements. Asymmetric Synthesis of (-)-Methyl Jasmonate
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Examples of mild, additive Pummerer rearrangements are given; one example involves asymmetric carbon-carbon bond formation as the key step for synthesis of (-)-methyl jasmonate.
- Posner, Gary H.,Asirvatham, Edward,Ali, Syed F.
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p. 542 - 543
(2007/10/02)
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- Gasphasen-Reaktionen, 21. Thermische Erzeugung von Alkyl- und Halogenketenen
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Thermal gas phase reactions for the generation of ketenes can be optimized PE-spectroscopically.To eliminate HX from acetyl derivatives R2CH-COX increasing temperatures are required in the sequence HO2CCH3 ca.HCl HBr H2O ca.ROH CH4.By adding NH3, HCl can be removed from the gaseous mixture and thus the PE spectra of pure alkyl ketenes R2C=C=O (R e.g.H, CH3, C2H5) may be recorded. "Fulvene ketene" (4) is obtained from cyclopentadienecarbonyl chloride (this from the dimer) and ethyleneketene (7) by pyrolysis of cyclopropyl spirosubstituted Meldrum's acid (6).Chloro- and bromoketenes are generated as follows: ClHC=C=O from ClH2C-COCl, Cl2C=C=O from Cl3C-COBr with Zn, BrHC=C=O from 2-bromocyclobutanone and NC-HC=C=O from NC-HC=C=O from NC-H2C-COCl.The PE spectra are assigned by radical cation state comparison based on MNDO calculations.
- Bock, Hans,Hirabayashi, Takakuni,Mohmand, Shamsher
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p. 2595 - 2608
(2007/10/02)
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- Reaction of Sulfene and Dichloroketene with Open-Chain N,N-Disubstituted α-Aminomethyleneketones. Synthesis of 4-Dialkylamino-3,4-dihydro-6-methyl-5-phenyl-1,2-oxathiin 2,2-Dioxides and of N,N-Disubstituted 4-Amino-3-chloro-(6-methyl-5-phenyl)(6-benzyl)-2H-pyran-2-ones
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Cycloaddition of sulfene to N,N-disubstituted 4-amino-3-phenyl-3-buten-2-ones (III) occurred in good yield only in the case of aliphatic N-substitution to give 4-dialkylamino-3,4-dihydro-6-methyl-5-phenyl-1,2-oxathiin 2,2-dioxides, whereas N,N-disubstituted 4-amino-1-phenyl-3-buten-2-ones (IV) did not react at all.Polar 1,4-cycloaddition of dichloroketene to III and IV occurred partly in the case of aromatic N-substitution, with the exception of the morpholino derivative IVd, giving in low yield N,N-disubstituted 4-amino-3,3-dichloro-3,4-dihydro-(6-methyl-5-phenyl)(6-benzyl)-2H-pyran-2-ones, which were dehydrochlorinated with DBN to the corresponding 4-amino-3-chloro-(6-methyl-5-phenyl)(6-benzyl)-2H-pyran-2-ones (VII) in good yield.In some cases of aliphatic N,N-disubstitution of III and IV, cycloaddition led directly to N,N-dialkyl derivatives VII in low yield.
- Bargagna, Alberto,Evangelisti, Filippo,Schenone, Pietro
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p. 111 - 116
(2007/10/02)
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- Reaction of Ketenes with N,N-Disubstituted α-Aminomethyleneketones. XI. Synthesis of 2H-Pyranobenzothiazole Derivatives
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Cycloaddition of dichloroketene to N,N-disubstituted 6-aminomethylene-5,6-dihydro-2-phenylbenzothiazol-7-(4H)ones gave in good yield N,N-disubstituted 4-amino-3,3-dichloro-3,4,5,6-tetrahydro-8-phenyl-2H-pyranobenzothiazol-2-ones II, which are derivatives of the new heterocyclic system 2H-pyranobenzothiazole.Dehydrochlorination with triethylamine of II afforded N,N-disubstituted 4-amino-3-chloro-5,6-dihydro-8-phenyl-2H-pyranobenzothiazol-2-ones III in good to moderate yield.The dimethylamino adduct was dehydrochlorinated in high yield by refluxing in toluene, whereas the diisopropylamino adduct gav e in low yield 6-(2,2-dichloroethylidene)-5,6-dihydro-2-phenylbenzothiazol-7-(4H)one with the triethylamine treatment.The dehydrochlorinated product IIId (NR2 = pyrrolidino) was obtained directly in low yield by cycloaddition of dichloroketene to the corresponding enaminone.Full aromatisation of IIIa,g 2 = N(CH3)2 and N(CH3)C6H5, respectively) to the corresponding N,N-disubstituted 4-amino-3-chloro-8-phenyl-2H-pyranobenzothiazol-2-ones was accomplished with DDQ in refluxing benzene.
- Mosti, Luisa,Menozzi, Giulia,Schenone, Pietro
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p. 1263 - 1267
(2007/10/02)
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- Dichloroketen; Gas Phase Preparation and Characterisation by Photoelectron Spectroscopy
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Dechlorination of trichloroacetyl chloride, CCl3COCl, at low pressure, leads to the formation of dichloroketen, Cl2C=C=O, which is studied by HeI photoelectron spectroscopy.
- Colbourne, David,Frost, David C.,McDowell, Charles A.,Westwood, Nicholas P. C.
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p. 250 - 251
(2007/10/02)
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