- Structural determination, DFT Calculation, and Formation Mechanism of Ethyl 2-Cyano-3-Alkoxypent-2-enoates synthesized via Ru-mediated coupling reaction between α,β-unsaturated acetals and cyanoacetate
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Ethyl 2-cyano-3-Alkoxypent-2-enoates were synthesized in moderate yields via the coupling reaction between α,β- unsaturated acetals and cyanoacetate, catalyzed by [RuHCl- (CO)(PPh3)3]. The E-And Z-isomers were separated and determined by X-ray crystallography for the first time. Structural distortion associated with steric hindrance around the tetrasubstituted alkene moiety was revealed: e.g., the C(carbonyl)C( α)C( β) angle expands to about 125°. Density functional theory calculation was performed, and the restricted B3LYP hybrid functional with the 6-31G(d,p) basis set was found to successfully elucidate the solid-state structure and conformation, as well as spectroscopic properties. A plausible formation mechanism was proposed, in which the Ru complex catalyzed the C=C bond migration of the α,β-unsaturated acetal to give the corresponding ketene acetal and assisted the subsequent condensation reaction with cyanoacetate to some extent.
- Seino, Hidetake,Kondo, Takumi,Mochizuki, Chihiro,Tokunaga, Ken,Yamaguchi, Motowo,Sato, Mitsunobu
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- A new method for the synthesis of mixed orthoesters from O-allyl acetals
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Two new methods for the synthesis of orthoesters and compounds containing an orthoester moiety (dihydroisoxazoles) are presented. Mixed orthoesters of general formulas RC(OR1)(OR2)2 and RC(OR1)(OR2)(O
- Krompiec, Stanis?aw,Penczek, Robert,Bujak, Piotr,Kubik, Ewelina,Malarz, Joanna,Penkala, Mateusz,Krompiec, Micha?,Ku?nik, Nikodem,Maciejewski, Hieronim
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experimental part
p. 1193 - 1195
(2009/06/28)
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- 2-Ethoxyvinyllithiums and diethoxyvinyllithiums: What makes them stable or fragile?
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The elusive (E)-2-ethoxyvinyllithium can be readily generated in tetrahydrofuran at -75 °C from (E)-1-bromo-2-ethoxyethylene by halogen/metal exchange and subsequently trapped with electrophiles. Alkylation opens a convenient entry to (E)-configurated enethers. (E)-2-Ethoxyvinyllithium decomposes rapidly at -50 °C whereas its (Z)-isomer, which lacks the possibility to eliminate lithium ethoxide in a favorable anti-periplanar process, is stable under the same conditions. (E)-1,2-Diethoxyvinyllithium even sustains reflux temperatures (approximately 75 °C). 2,2-Diethoxyvinyllithium and (Z)-1,2-diethoxyvinyllithium can be conserved at 0 °C although this time loss of alcoholate can occur in the anti-mode. Obviously it matters whether the energy-rich ethoxyacetylene is formed as the elimination product or simple acetylene, as in the case of (E)-2-ethoxyvinyllithium.
- Schlosser, Manfred,Wei, Heng-Xu
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p. 1735 - 1742
(2007/10/03)
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- 2,2-Di(ethoxy)vinyllithium: A synthetic equivalent of the ethyl acetate anion
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2,2-Diethoxyvinyllithium can be readily generated from 2-bromo-1,1,-diethoxyethylene by treatment with butyllithium. When dissolved in tetrahydrofuran, it can be stored at -25°C for hours, but decomposes rapidly at 0°C.
- Wei,Schlosser
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p. 2771 - 2772
(2007/10/03)
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- 12-hetero substituted 6,11-ethano-6,11-dihydrobenzo (b) quinolizinium salts and compositions and method of use thereof
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1-Hetero substituted 6,11-ethano-6,11-dihydrobenzo[b]quinolizinium salts, pharmaceutical compositions containing them, and methods for the treatment or prevention of neurodegenerative disorders or neurotoxic injuries utilizing them.
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- 13C NMR study of the structures of some acyclic and cyclic ketene acetals
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A 13C NMR study of the spatial structures of some acyclic and cyclic ketene acetals (for example, ketene dimethyl acetal and 2-methylene-1,3-dioxolane) has been carried out. The conclusions obtained are based on observation of the effect of structural changes on the 13C NMR chemical shift of the β carbon on the ketene moity. Since the extent of p-π conjugation and hence the 13C chemical shift of this carbon depend on the spatial orientation of the alkoxy groups about the O-C(sp2) bonds, the shift concerned may be used as a measure of the planarity of the system. The most stable retamers of ketene dimethyl acetal are s-cis,s-cis (planar) and s-cis,gauche (slightly nonplanar), in the order of decreasing stability. For ketene dialkyl acetals, the relative stability of the planar s-cis,s-cis form decreases with increasing bulkiness of the alkyl groups, but at least for primary and secondary alkyl groups, the s-cis,s-cis rotamer appears to be the most favored species. The conformations of 5- to 8-membered cyclic ketene acetals are discussed and compared with those of the corresponding cyclic vinyl ethers and hydrocarbons.
- Taskinen,Pentikaeinen
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p. 2365 - 2370
(2007/10/04)
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