- Stereochemistry of the thermal conversion of 1-vinyl-2,3-cis-dideuteriocyclobutane to butadiene and 1,2-dideuterioethylenes
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This study has examined the stereochemistry of the decomposition at 900-1000 K in a single-pulse shock tube of 1-vinyl-2,3-cis-dideuteriocyclobutane to ethylenes and buta-1,3-dienes. The deuterated ethylenes formed during the decomposition, CHD=CH2, (E)-CHD=CHD, and (Z)-CHD=CHD, were quantified via two independent techniques, FTIR and IR absorption spectroscopy using a tunable diode laser spectrometer. The results of both analyses indicated that equal amounts of (E)-CHD=CHD and (Z)-CHD=CHD were formed from the cis-labeled reactant. In an earlier shock tube study of the decomposition at 1000-1200 K of two deuterium-labeled cyclohexenes to ethylenes plus buta-1,3-dienes, a pathway via a vinylcyclobutane intermediate was implicated in a significant fraction of the decomposition events; the measured ratios of (E)-CHD=CHD to (Z)-CHD=CHD in that study were consistent with a complex mechanistic model in which the stereochemistry of deuterium labels in the cyclohexene reactant was lost in ethylene products formed via vinylcyclobutane. The present results provide additional support for that model.
- Lewis, David K.,Hutchinson, Avery,Lever, Steven J.,Spaulding, Eric L.,Bonacorsi Jr., Samuel J.,Baldwin, John E.
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p. 233 - 237
(2007/10/03)
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- Synthesis of 7-Fluoro-2,4-methylene-17,20-dimethylprostacyclins. Novel Stable Prostacyclin Analogs as Potent Anti-anginal Agents
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Synthesis of new stable fluoroprostacyclins, 7-fluoro-2,4-methylene-17,20-dimethylprostacyclins (1, 2) with potent and long-lasting anti-anginal activities has been achieved.The cyclobutylene prostaglandin skeleton 10 was constructed efficiently according
- Matsumura, Yasushi,Shimada, Toyomichi,Nakayama, Toshiaki,Urushihara, Masahiro,Asai, Tomoyuki,et al.
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p. 8771 - 8782
(2007/10/02)
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- SYNTHESIS OF SQ-32,829, A NEW NUCLEOSIDE ANTIVIRAL AGENT
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The guanine-containing cyclobutane nucleoside analog SQ-32,829 (1) was synthesized in 8 steps from 1,1-cyclobutanedicarboxylic acid(3).
- Jacobs, G. A.,Tino, J. A.,Zahler, R.
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p. 6955 - 6958
(2007/10/02)
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- Prediction and Experimental Verification of the Stereoselective Electrocyclization of 3-Formylcyclobutene
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3-Formylcyclobutene has been synthesized from cyclobutene-1, 1-dicarboxylic acid; it opens at 25-70 deg C with an activation energy of 27 +/- 1 kcal/mol to give exclusively (> 98percent) the Z product, in accord with predictions.
- Rudolf, Klaus,Spellmeyer, David C.,Houk, K. N.
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p. 3708 - 3710
(2007/10/02)
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- An Electron Spin Resonance Study of Pentadienyl and Related Radicals: Homolytic Fission of Cyclobut-2-enylmethyl Radicals
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Pentadienyl radicals were generated from penta-1,4-diene and cis and trans-1-bromopenta-2,4-diene, and were observed in the E,E (1) and E,Z (2) conformations in hydrocarbon solution by e.s.r. spectroscopy.The E,Z-radicals are converted into the E,E-radicals at T > ca.170 K, but the E,E-radicals are not converted into the E,Z-radicals in the accessible temperature range.From the estimated barrier to rotation in E,Z-pentadienyl radicals the methane based stabilization energy (E8Me-H) was estimated to be 104 kJ mol-1.Pentadienyl radicals can also be obtained from ring-opening of cyclobut-2-enylmethyl radicals (3).Bromine abstraction from cyclobut-2-enyl methyl bromide by triethylsilyl radicals gave cyclobut-2-enylmethyl radicals at temperatures below ca.230 K.Above this temperature homolytic fission of the cyclobutene ring occured and pentadienyl radicals in the E,E-conformation were detected by e.s.r.Initially,E,Z-pentadienyl radicals must be formed, but at the temperature of ring fission these are converted into the E,E-radicals and so are not observed.Hydrogen abstraction from neither 3-methylcyclobutene nor from bicyclopentane yields (3) : instead 3-methylcyclobutenyl radicals and cyclopent-3-enyl radicals are formed, respectively.E.s.r.parameters are also reported for a range of substituted pentadienyl radicals generated from the corresponding 1,4-dienes.Of these radicals only 3-trimethylsiloxypentadienyl was observed in two conformations.
- Davies, Alwyn G.,Griller, David,Ingold, Keith U.,Walton, John C.,Lindsay, David A.
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p. 633 - 641
(2007/10/02)
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