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《Tetrahedron letters》1987,28(51):6489-6492
Bicyclo[3.3.0]oct-2-ene derivatives with high optical purities (87–99% e.e) were obtained by asymmetric elimination of the trifluoromethanesulfonates (10, 11, 12) by chiral N,N-dimethyl-1-phenethylamine. 相似文献
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Nelsen SF Reinhardt LA Tran HQ Clark T Chen GF Pappas RS Williams F 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(5):1074-1081
The bicyclo[2.2.2]oct-2-ene radical cation (1(.+)) exhibits matrix ESR spectra that have two very different types of gamma-exo hydrogens (those hydrogens formally in a W-plan with the alkene pi bond), a(2H) about 16.9 G and a(2H) about 1.9 G, instead of the four equivalent hydrogens as would be the case in an untwisted C(2v) structure. Moreover, deuterium substitution showed that the vinyl ESR splitting is not resolved (and under about 3.5 G); this is also a result of the twist. Enantiomerization of the C(2) structures is rapid on the ESR timescale above 110 K (barrier estimated at 2.0 kcalmol(-1)). Density functional theory calculations estimate the twist angle at the double bond to be 11-12 degrees and the barrier as 1.2-2.0 kcalmol(-1). Single-configuration restricted Hartree-Fock (RHF) calculations at all levels that were tried give untwisted C(2v) structures for 1(.+), while RHF calculations that include configuration interactions (CI) demonstrate that this system undergoes twisting because of a pseudo Jahn-Teller effect (PJTE). Significantly, twisting does not occur until the sigma-orbital of the predicted symmetry is included in the CI active space. UHF calculations at all levels that include electron correlation (even semiempirical) predict twisting at the alkene pi bond because they allow the filled alpha and the beta hole of the SOMO to have different geometries. The 2,3-dimethylbicyclo[2.2.2]oct-2-ene radical cation (2(.+)) is twisted significantly less than 1(.+), but has a similar temperature for maximum line broadening. Neither the 2,3-dioxabicyclo[2.2.2]octane radical cation (3(.+)) nor its 2,3-dimethyl-2,3-diaza analogue (5(.+)) shows any evidence of twisting. Calculations show that the orbital energy gap between the SOMO and PJTE-active orbitals for 3(.+) is too large for significant PJTE stabilization to occur. 相似文献
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Powers DC Leber PA Gallagher SS Higgs AT McCullough LA Baldwin JE 《The Journal of organic chemistry》2007,72(1):187-194
At 300 degrees C, bicyclo[4.2.0]oct-2-ene (1) isomerizes to bicyclo[2.2.2]oct-2-ene (2) via a formal [1,3] sigmatropic carbon migration. Deuterium labels at C7 and C8 were employed to probe for two-centered stereomutation resulting from C1-C6 cleavage and for one-centered stereomutation resulting from C1-C8 cleavage, respectively. In addition, deuterium labeling allowed for the elucidation of the stereochemical preference of the [1,3] migration of 1 to 2. The two possible [1,3] carbon shift outcomes reflect a slight preference for migration with inversion rather than retention of stereochemistry; the si/sr product ratio is approximately 1.4. One-centered stereomutation is the dominant process in the thermal manifold of 1, with lesser amounts of fragmentation and [1,3] carbon migration processes being observed. All of these observations are consistent with a long-lived, conformationally promiscuous diradical intermediate. 相似文献
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Applying the method of maximum overlap, the hybridization in bicyclo[2.1.0]pent-2-ene is determined. In addition, upon comparing these results with those of cyclobutene, cyclopropane, Dewar benzene and bicyclo[1.1.0]butane, it is found that the hybrids calculated by the method of maximum overlap are transferable between parts of molecules for which the structural features are similar. 相似文献
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The formation and trapping of bicyclo[3.1.0]hex-(1,5)-ene and bicyclo[4.1.0]hept-(1,6)-ene from the corresponding vicinal dibromides is described. 相似文献
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Ershov O. V. Lipin K. V. Belikov M. Yu. Ievlev M. Yu. 《Russian Journal of Organic Chemistry》2019,55(7):1009-1012
Russian Journal of Organic Chemistry - Tetracyanoethylene adducts with ketones, 4-oxoalkane-1,1,2,2-tetracarbonitriles reacted with hydrogen chloride or phosphorus(III) chloride in 1,4-dioxane to... 相似文献
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Ohno H Mizutani T Kadoh Y Aso A Miyamura K Fujii N Tanaka T 《The Journal of organic chemistry》2007,72(12):4378-4389
Thermal [2 + 2] cycloaddition of allenes with an additional multiple bond is described. By simply heating the allenenes or allenynes having a three-atom tether in an appropriate solvent such as dioxane or DMF, the distal double bond of the allenic moiety regioselectively participates in the cycloaddition to form bicyclo[4.2.0]oct-5-ene derivatives in good to excellent yields. In all the reactions of allenenes, the olefin geometry was completely transferred to the cycloadducts. While the reaction of terminal allenes afforded bicyclic cyclobutane derivatives as a single isomer, the cycloaddition of some internal allenes with axial chirality yielded a diastereomeric mixture of cycloadducts. These results are in good accordance with the stepwise mechanism through a biradical intermediate with a coplanar allyl radical. 相似文献
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Issifu I. Harruna Malcolm B. Polk 《Journal of polymer science. Part A, Polymer chemistry》1988,26(8):2171-2182
Random copolyesters based on 1,4-benzenedimethanol, trans-1,4-cyclohexanedimethanol, and 1,4-bicyclo[2.2.2]octanedimethanol as spacers in ratios of 2 : 3 of the mesogenic group, bicyclo[2.2.2]oct-2-ene-1,4-diol were prepared and characterized. The copolyesters containing the 1,4-benzenedimethanol moiety formed a more brightly colored birefringent fluid in the melt. 相似文献
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Baldwin JE Gallagher SS Leber PA Raghavan AS Shukla R 《The Journal of organic chemistry》2004,69(21):7212-7219
The thermal conversion of cis-bicyclo[4.2.0]oct-7-ene to cis,cis-1,3-cyclooctadiene might involve a direct disrotatory ring opening, or it might possibly take place by way of cis,trans-1,3-cyclooctadiene. This cis,trans-diene might possibly form the more stable cis,cis isomer through a [1,5] hydrogen shift or a trans-to-cis isomerization about the trans double bond. Deuterium kinetic isotope effect determinations for the isomerizations of 2,2,5,5-d(4)-bicyclo[4.2.0]oct-7-ene and 7,8-d(2)-bicyclo[4.2.0]oct-7-ene rule out these two alternatives because the observed effects are much smaller than would be anticipated for these mechanisms: k(H)/k(D)(d(4)) at 250 degrees C is 1.17 (1.04 per D), and k(H)/k(D)(d(2)) at 238 degrees C is 1.20 (1.10 per D). The direct disrotatory ring opening route remains the preferred mechanism. 相似文献
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Two new substituted [1.1.1]propellanes have been generated from the corresponding bicyclo[1.1.0]butanes in either single-step (1a) or four-step procedures (1b). The observed degree of double lithiation of the bicyclo[1.1.0]butanes is discussed in the context of DFT computational results. Addition reactions across the central C(1)-C(3) bonds of the propellanes were studied. Only the propellane 1b gave the biacetyl addition product. 相似文献
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Joseph F. Chiang Raymond L. Chiang Martin T. Kratus 《Journal of Molecular Structure》1975,26(2):175-188
The average molecular structures of 2,3-diazabicyclo[2.2.1]hept-2-ene and 2,3-diazabicyclo[2.2.2] oct-2-ene have been determined by electron diffraction in the gas phase. The structural parameters were obtained by applying a least squares analysis on the molecular scattering intensity functions. For 2,3-diazabicyclo[2.2.1]hept-2-ene, Cs symmetry was assumed in calculating the geometry of the molecule. The parameters thus determined are: N3=N2 = 1.221 Å, N3- C4 = 1.445 Å, C4-C5 = 1.538 Å, C-H(ave.) = 1.112 Å, < C1N2N3 = 116.3°, < N3C4C5 = 105.2°, < C1C4C5 = 71.5°, C4-C7 = 1.547 Å, C5-C6 = 1.530 Å, < C1C7C4 = 108.0°. For 2,3-diazabicyclo[2.2.2]oct-2-ene, C2vsymmetry was assumed. The geometrical parameters are: N3 = N2 = 1.243 Å, N3-C4 = 1.473 Å, C4-C5 = 1.550 Å, C5-C6 = 1.516 Å, C-H(ave.) = 1.119 Å,< C1N2N3 = 115.1°, < N3C4C5 = 109.1°, < C6C1C4 = 71.6°. 相似文献
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Application of the intramolecular Wadsworth-Emmons reaction to bicyclo[3..3.0]oct-2-en-3-ones results in the formation of a novel dimer (11) of the parent member (6) whose structure has been determined by X-ray crystallography. 相似文献
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Graeme Butt N. Pirzada Ronald D. Topsom William Adcock Anil N. Abeywickrema 《Tetrahedron letters》1982,23(21):2161-2162
The carbon-13 substituent chemical shifts of 4-substituted bicyclo[2.2.2]oct-1-yl cyanides are a linear function of the substituent inductive parameters. 相似文献
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Issifu I. Harruna Malcolm B. Polk 《Journal of polymer science. Part A, Polymer chemistry》1990,28(2):285-298
Homopolyesters based on bicyclo[2.2.2]oct-2-ene as a mesogenic group were prepared and characterized. The use of bicyclo[2.2.2]oct-2-ene in these homopolyesters lowered the symmetry of the resulting systems enough to lead to the observation of melting behavior. 相似文献
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Angel-Manuel Montaa Albert Moyano Miquel A. Pericas Felix Serratosa 《Tetrahedron》1985,41(24):5995-6003
Reaction of bicyclo[3.3.0]oct-2-ene with different hexacarbonyl dicobalt complexes of propargyl derivatives leads, under a great variety of experimental conditions, to the exclusive formation of angularly fused triquinanes, the corresponding reduced products being formed if the reaction is run at high temperature. The intermediacy of a π-allyl complex is suggested in order to account for these results, as well as for the presence of minor amounts of Diels-Alder adducts in the reaction mixture. 相似文献